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THE
PHILOSOPHY OF HEALTH;

OR,

AN EXPOSITION

OF THE

PHYSICAL AND MENTAL CONSTITUTION OF MAN,

WITH A VIEW TO THE PROMOTION OF

HUMAN LONGEVITY AND HAPPINESS.

BY

SOUTHWOOD SMITH, M.D.,

Physician to the London Fever Hospital, to the Eastern Dispensary, and to the Jews' Hospital.

IN TWO VOLUMES. Vol. I.

THIRD EDITION.

LONDON:

C. COX, 12, KING WILLIAM STREET, STRAND.

1847.

London: Printed by W. Clowes and Sons, Stamford Street.

CONTENTS OF VOL. I.

INTRODUCTION.

The object of the present work is to give a brief and plain account of the structure and functions of the body, chiefly with reference to health and disease. This is intended to be introductory to an account of the constitution of the mind, chiefly with reference to the development and direction of its powers. There is a natural connexion between these subjects, and an advantage in studying them in their natural order. Structure must be known before function can be understood: hence the science of physiology is based on that of anatomy. The mind is dependent on the body: hence an acquaintance with the physiology of the body should precede the study of the physiology of the mind. The constitution of the mind must be understood before its powers and affections can be properly developed and directed: hence a knowledge of the physiology of the mind is essential to a sound view of education and morals.

In the execution of the first part of this work, that which relates to the organization of the body, a formidable difficulty presents itself at the outset. The explanation of structure is easy when the part described can be seen. The teacher of anatomy finds no difficulty in communicating to the student a clear and exact knowledge of the structure of an organ; because, by the aid of dissection, he resolves the various complex substances, of which it is built up, into their constituent parts, and demonstrates the relation of these elementary parts to each other. But the case is different with him who attempts to convey a knowledge of the structure of an organ merely by the description of it. The best conceived and executed drawing is a most inadequate substitute for the object itself. It is impossible wholly to remove this difficulty: what can be done, by the aid of plates, to lessen it, is here attempted. A time may come when the objects themselves will be more generally accessible: meanwhile, the description now given of the chief organs of the body may facilitate the study of their structure to those who have an opportunity of examining the organs themselves, and will, it is hoped, enable every reader at once to understand much of their action.

Physical science has become the subject of popular attention, and men of the highest endowments, who have devoted their lives to the cultivation of this department of knowledge, conceive that they can make no better use of the treasures they have accumulated, than that of diffusing them. Of this part of the great field of knowledge, to make "the rough places plain, and the crooked places straight," is deemed a labour second in importance only to that of extending the boundaries of the field itself. But no attempt has hitherto been made to exhibit a clear and comprehensive view of the phenomena of life; the organization upon which those phenomena depend; the physical agents essential to their production, and the laws, as far as they have yet been discovered, according to which those agents act. The consequence is, that people in general, not excepting the educated class, are wholly ignorant of the structure and action of the organs of their own bodies, the circumstances which are conducive to their own health, the agents which ordinarily produce disease, and the means by which the operation of such agents may be avoided or counteracted; and they can hardly be said to possess more information relative to the connexion between the organization of the body and the qualities of the mind, the physical condition and the mental state; the laws which regulate the production, combination, and succession of the trains of pleasurable and painful thought, and the rules deducible from those laws, having for their object such a determination of voluntary human conduct, as may secure the pleasurable and avoid the painful.

Yet nothing would seem a fitter study for man than the nature of man in this sense of the term. A knowledge of the structure and functions of the body is admitted to be indispensable to whoever undertakes, as the business of his profession, to protect those organs from injury, and to restore their action to a sound state when it has become disordered; but surely some knowledge of this kind may be useful to those who have no intention to practise physic, or to perform operations in surgery; may be useful to every human being, to enable him to take a rational care of his health, to make him observant of his own altered sensations, as indications of approaching sickness; to give him the power of communicating intelligibly with his medical adviser respecting the seat and the succession of those signs of disordered function, and to dispose and qualify him to co-operate with his physician in the use of the means employed to avert impending danger, or to remove actual disease.

But if to every human being occasions must continually occur, when knowledge of this kind would be useful, the possession of it seems peculiarly necessary to those who have the exclusive care of infancy, almost the entire care of childhood, a great part of the care of the sick, and whose ignorance, not the less mischievous because its activity is induced by affection, constantly endangers, and often defeats, the best concerted measures of the physician.

The bodily organization and the mental powers of the child depend mainly on the management of the infant; and the intellectual and moral aptitudes and qualities of the man have their origin in the predominant states of sensation, at a period far earlier in the history of the human being than is commonly imagined. The period of infancy is divided by physiologists into two epochs; the first, commencing from birth, extends to the seventh month: the second, commencing from the seventh month, extends to the end of the second year, at which time the period of infancy ceases, and that of childhood begins. The first epoch of infancy is remarkable for the rapidity of the development of the organs of the body: the processes of growth are in extreme activity; the formative predominates over the sentient life, the chief object of the action of the former being to prepare the apparatus of the latter. The second epoch of infancy is remarkable for the development of the perceptive powers. The physical organization of the brain, which still advances with rapidity, is now capable of a greater energy, and a wider range of function. Sensation becomes more exact and varied; the intellectual faculties are in almost constant operation; speech commences, the sign, and, to a certain extent, the cause of the growing strength of the mental powers; the capacity of voluntary locomotion is acquired, while passion, emotion, affection, come into play with such constancy and energy, as to exert over the whole economy of the now irritable and plastic creature a prodigious influence for good or evil. If it be, indeed, possible to make correct moral perception, feeling, and conduct, a part of human nature, as much a part of it as any sensation or propensity—if this be possible for every individual of the human race, without exception, to an extent which would render all more eminently and consistently virtuous than any are at present (and of the possibility of this, the conviction is the strongest in the acutest minds which have studied this subject the most profoundly), preparation for the accomplishment of this object must be commenced at this epoch. But if preparation for this object be really commenced, it implies, on the part of those who engage in the undertaking, some degree of knowledge; knowledge of the physical and mental constitution of the individual to be influenced; knowledge of the mode, in which circumstances must be so modified in adaptation to the nature of the individual being, as to produce upon it, with uniformity and certainty, a given result. The theory of human society, according to its present institutions, supposes that this knowledge is possessed by the mother; and it supposes, further, that this adaptation will actually take place in the domestic circle through her agency. Hence the presumed advantage of having the eye of the mother always upon the child; hence the apprehension of evil so general, I had almost said instinctive, whenever it is proposed to take the infant, for the purpose of systematic physical and mental discipline, from beyond the sphere of maternal influence. But society, which thus presumes that the mother will possess the power and the disposition to do this, what expedients has it devised to endow her with the former, and to secure the formation of the latter? I appeal to every woman whose eye may rest on these pages. I ask of you, what has ever been done for you to enable you to understand the physical and mental constitution of that human nature, the care of which is imposed upon you? In what part of the course of your education was instruction of this kind introduced? Over how large a portion of your education did it extend? Who were your teachers? What have you profited by their lessons? What progress have you made in the acquisition of the requisite information? Were you at this moment to undertake the guidance of a new-born infant to health, knowledge, goodness, and happiness, how would you set about the task? How would you regulate the influence of external agents upon its delicate, tender, and highly-irritable organs, in such a manner as to obtain from them healthful stimulation, and avoid destructive excitement? What natural and moral objects would you select as the best adapted to exercise and develope its opening faculties? What feelings would you check, and what cherish? How would you excite aims; how would you apply motives? How would you avail yourself of pleasure as a final end, or as the means to some further end? And how would you deal with the no less formidable instrument of pain? What is your own physical, intellectual, and moral state, as specially fitting you for this office? What is the measure of your own self-control, without a large portion of which no human being ever yet exerted over the infant mind any considerable influence for good? There is no philosopher, however profound his knowledge, no instructor, however varied and extended his experience, who would not enter upon this task with an apprehension proportioned to his knowledge and experience; but knowledge which men acquire only after years of study, habits which are generated in men only as the result of long-continued discipline, are expected to come to you spontaneously, to be born with you, to require on your part no culture, and to need no sustaining influence.

But, indeed, it is a most inadequate expression of the fact, to say that the communication of the knowledge, and the formation of the habits which are necessary to the due performance of the duties of women, constitute no essential part of their education: the direct tendency of a great part of their education is to produce and foster opinions, feelings, and tastes, which positively disqualify them for the performance of their duties. All would be well if the marriage ceremony, which transforms the girl into the wife, conferred upon the wife the qualities which should be possessed by the mother. But it is rare to find a person capable of the least difficult part of education, namely, that of communicating instruction, even after diligent study, with a direct view to teaching; yet an ordinary girl, brought up in the ordinary mode, in the ordinary domestic circle, is intrusted with the direction and control of the first impressions that are made upon the human being, and the momentous, physical, intellectual, and moral results that arise out of those impressions!

I am sensible of the total inadequacy of any remedy for this evil, short of a modification of our domestic institutions. Mere information, however complete the communication of it, can do little beyond affording a clearer conception of the end in view, and of the means fitted to secure it. Even this little, however, would be something gained; and the hope of contributing, in some degree, to the furtherance of this object, has supplied one of the main motives for undertaking the present work. Meantime, women are the earliest teachers; they must be nurses; they can be neither, without the risk of doing incalculable mischief, unless they have some understanding of the subjects about to be treated of. On these grounds I rest their obligation to study them; and I look upon that notion of delicacy, which would exclude them from knowledge calculated, in an extraordinary degree, to open, exalt, and purify their minds, and to fit them for the performance of their duties, as alike degrading to those to whom it affects to show respect, and debasing to the mind that entertains it.

Though each part of this work will be made as complete in itself as the author is capable of rendering it, and to that extent independent of any other part, yet there will be found to be a strict connexion between the several portions of the whole; and greatly as the topics included in the latter differ from those which form the earlier subjects, the advantage of having studied the former before the latter are entered on, will be felt precisely as the word study can be justly applied to the operation of the mind on such matters.

In the expository portion of the work I have not been anxious to abstain from the employment of technical terms, when a decidedly useful purpose was to be obtained by the introduction of them; but I have been very careful to use no such term without assigning the exact meaning of it. A technical term unexplained is a dark spot on the field of knowledge; explained, it is a clear and steady light.

In order really to understand the states of health and disease, an acquaintance with the nature of organization, and of the vital processes of which it is the seat and the instrument, is indispensable: it is for this reason that the exposition of structure and function, attempted in this first part of the work, is somewhat full; but there cannot be a question that, if it accomplish its object, it will not only enable the account of health and disease in the subsequent part of it to be much more brief, but that it will, at the same time, render that account more intelligible, exact, and practical.

S. S.

THE
PHILOSOPHY OF HEALTH.

CHAPTER I.

Characters by which living beings are distinguished from inorganic bodies—Characters by which animals are distinguished from plants—Actions common to plants and animals—Actions peculiar to animals—Actions included in the organic circle—Actions included in the animal circle—Organs and functions defined—Action of physical agents on organized structures—Processes of supply, and processes of waste—Reasons why the structure of the animal is more complex than that of the plant.

The distinction between a living being and an inorganic body, between a plant and a stone, is, that the plant carries on a number of processes which are not performed by the stone. The plant absorbs food, converts its food into its own proper substance, arranges this substance into bark, wood, vessels, leaves, and other organized structures; grows, arrives at maturity, and decays; generates and maintains a certain degree of heat; derives from a parent the primary structure and the first impulse upon which these varied actions depend; gives origin to a new being similar to itself, and, after a certain time, terminates its existence in death.

No such phenomena are exhibited by the stone; it neither absorbs food, nor arranges the matter of which it is composed into organized structure; nor grows, nor decays, nor generates heat, nor derives its existence from a parent, nor gives origin to a new being, nor dies. Nothing analogous to the processes by which these results are produced, is observable in any body that is destitute of life; all of them are carried on by every living creature. These processes are, therefore, denominated vital, and, being peculiar to the state of life, they afford characters by which the living being is distinguished from the inorganic body.

In like manner the distinction between an animal and a plant is, that the animal possesses properties of which the plant is destitute. It is endowed with two new and superior powers, to which there is nothing analogous in the plant; namely, the power of sensation, and the power of voluntary motion; the capacity of feeling, and the capacity of moving from place to place as its feeling prompts. The animal, like the plant, receives food, transforms its food into its own proper substance, builds this substance up into structure, generates, and maintains a certain temperature, derives its existence from a parent, produces an offspring like itself, and terminates its existence in death. Up to this point the vital phenomena exhibited by both orders of living creatures are alike: but at this point the vital processes of the plant terminate, while those of the animal are extended and exalted by the exercise of the distinct and superior endowments of sensation and voluntary motion. To feel, and to move spontaneously, in accordance with that feeling, are properties possessed by the animal, but not by the plant; and therefore these properties afford characters by which the animal is distinguished from the plant.

The two great classes of living beings perform, then, two distinct sets of actions: the first set is common to all living creatures; the second is peculiar to one class: the first set is indispensable to life; the second is necessary only to one kind of life, namely, the animal. The actions included in the first set, being common to all living or organized creatures, are called ORGANIC; the actions included in the second class, belonging only to one part of living or organized creatures, namely, animals, are called ANIMAL. The ORGANIC actions consist of the processes by which the existence of the living being is maintained, and the perpetuation of its species secured: the ANIMAL actions consist of the processes by which the living being is rendered percipient, and capable of spontaneous motion. The ORGANIC processes comprehend those of nutrition, respiration, circulation, secretion, excretion, and reproduction; the first five relate to the maintenance of the life of the individual being; the last to the perpetuation of its species. The ANIMAL processes comprehend those of sensation and of voluntary motion, often denominated processes of relation, because they put the individual being in communication with the external world. There is no vital action performed by any living creature which may not be included in one or other of these processes, or in some modification of some one of them. There is no action performed by any inorganic body which possesses even a remote analogy to either of these vital processes. The line of demarcation between the organic and the inorganic world is, therefore, clear and broad; and the line of demarcation between the two great divisions of the organic world, between the inanimate and the animate, that is, between plants and animals, is no less decided: for, of the two sets of actions which have been enumerated, the one, as has just been stated, is common to the whole class of living beings, while the second set is peculiar to one division of that class. The plant performs only the organic actions: all the vital phenomena it exhibits are included in this single circle; it is, therefore, said to possess only organic life: but the animal performs both organic and animal actions, and is therefore said to possess both organic and animal life.

Both the organic and the animal actions are accomplished by means of certain instruments, that is, organized bodies which possess a definite structure, and which are moulded into a peculiar form. Such an instrument is called an organ, and the action of an organ is called its function. The leaf of the plant is an organ, and the conversion of sap by the leaf into the proper juice of the plant, by the process called respiration, is the function of this organ. The liver of the animal is an organ; and the conversion of the blood that circulates through it into bile, by the process of secretion, is its function. The brain is an organ; the sentient nerve in communication with it is also an organ. The extremity of the sentient nerve receives an impression from an external object, and conveys it to the brain, where it becomes a sensation. The transmission of the impression is the function of the nerve; the conversion of the impression into a sensation is the function of the brain.

The living body consists of a congeries of these instruments or organs: the constituent matter of these organs is always partly in a fluid and partly in a solid state. Of the fluids and solids which thus invariably enter in combination into the composition of the organs, the fluids may be regarded as the primary and essential elements, for they are the source and the support of the solids. There is no solid which is not formed out of a fluid; no solid which does not always contain, as a constituent part of it, some fluid, and none which is capable of maintaining its integrity without a continual supply of fluids.

Whatever be the intimate composition of the fluids out of which the solids are formed, the investigation of which is more difficult than that of the solids and the nature of which is therefore less clearly ascertained, it is certain that all the matter which enters into the composition of the solid is disposed in a definite order. It is this disposition of the constituent matter of the living solid in a definite order that constitutes the arrangement so characteristic of all living substance. Definite arrangements are combined in definite modes, and the result is what is termed organization. From varied arrangements result different kinds of organized substances, each endowed with different properties, and exhibiting peculiar characters. By the recombination of these several kinds of organized substances, in different proportions and different modes, are formed the special instruments, or organs, of which we have just spoken; while it is the combining, or the building up of these different organized substances into organs, that constitutes structure.

In the living body, not only is each distinct organ alive, but, with exceptions so slight that they need not be noticed here, every solid which enters into the composition of the organ is endowed with vital properties. This is probably the case with the primary substances or tissues which compose the several organs of the plant; but that the animal solids are alive is indubitable; nay, the evidence is complete, that many even of the animal fluids possess vitality. The blood in the animal is as truly alive as the brain, and the bone as the flesh. The organized body, considered as a whole, is the seat of life; but life also resides in almost every component part of it.

Yet the matter out of which these living substances is formed is not alive. By processes of which we know nothing, or, at least, of which we see only the first steps,—matter, wholly destitute of life, is converted into living substance. The inorganic matter, which is the subject of this wonderful transformation, is resolvable into a very few elementary substances. In the plant, these substances consist of three only, namely, oxygen, hydrogen, and carbon. The first two are aëriform or gaseous bodies; the last is a solid substance, and it is of this that the plant is chiefly composed: hence the basis of the plant is a solid. The elementary bodies, into which all animal substance is resolvable, are four, namely, azote, oxygen, hydrogen, and carbon. Into every animal fluid and solid this new substance azote enters so largely, that it may be considered as the fundamental and distinctive element of the animal organization: hence the basis of the animal is an aëriform or gaseous fluid. The animal is composed of air, the plant of solid matter; and this difference in their elementary nature gives origin to several distinctive characters between the plant and the animal, in addition to those which have been already stated.

Thus the characters of the plant are solidity, hardness, fixedness, and durability; while the animal is comparatively fluid, soft, volatile, and perishable; and the reason is now manifest. The basis of the animal being an aëriform fluid, its consistence is softer than that of the plant, the basis of which is a firm solid; and, at the same time, the component elements of the animal being more numerous than those of the plant, and the fluidity of these elements, and of the compounds they form, greatly favouring their action and reaction on each other and on external agents, the animal body is more volatile and perishable during life, and more readily decomposed after death.

It has been stated, that the object of every structure or organ of the living body, is the performance of some special action or function,—the ultimate object of the fluids being the production of the solids; the ultimate object of the solids being the formation of organs; the ultimate object of organs being the performance of actions or functions; while it is in the performance of actions or functions that life consists. Functions carried on by organs; organs in action; special organs performing definite actions, this it is that constitutes the state of life. Every particle of matter which enters into the composition of the living body has thus its own place, forming, or destined to form, a constituent part of some organ; every organ has its own action; all the organs of the body form the body; and all the actions of all the organs constitute the aggregate of the vital phenomena.

Every organ is excited to action, or its function is called into operation by means of some external body. The external bodies capable of exciting and maintaining the functions of living organs, consist of a definite class. Because these bodies belong to that department of science which is called physical, they are termed physical agents. They are air, water, heat, cold, electricity, and light. Without the living organ, the physical agent can excite no vital action: without the physical agent, the living organ can carry on no vital process. The plant cannot perform the vital process of respiration without the leaf, nor, with the leaf, without air. The physical agent acts upon the living organ; the living organ reacts upon the physical agent, and the action between both is definite. In the lung of the animal a certain principle of the air unites, in definite proportions, with a certain principle of the blood; the oxygen of the air combines with the carbon of the blood; the air is changed by the abstraction of its oxygen; the blood is changed by the abstraction of its carbon. Atmospheric air goes to the lung, but atmospheric air does not return from the lung; it is converted into a new substance by the action of the organ: it is changed into carbonic acid by the union of a given quantity of oxygen, which it transmits to the organ, with a given quantity of carbon which the organ conveys to it. Venous blood goes to the lung, but venous blood does not return from the lung; it is converted, by the instrumentality of the organ, into a new substance, into arterial blood, by giving to the air carbon, and by receiving from the air oxygen. In this manner the change in the physical agent is definite and uniform; and the change in the living substance is equally definite and uniform.

It is this determinate interchange of action between the living organ and the physical agent that constitutes what is termed a vital process. All vital processes are carried on by living organs; the materials employed in all vital processes are physical agents; the processes themselves are vital functions. All the changes produced by all the organs of the plant upon physical agents, and all the changes produced by all physical agents upon the organs of the plant, constitute all the vital processes of the plant—comprehend the whole sum of its vital phenomena. The root, the trunk, the woody substance, the bark, the ascending vessels bearing sap, the descending vessels bearing secreted fluids, the leaves, the flowers, these are the living organs of the plant. Air, water, heat, cold, electricity, light, these are the physical agents which produce in these organs definite changes, and which are themselves changed by them in definite modes; and the whole of these changes, taken together, comprehend the circle of actions, or the range of functions performed by this living being.

In the state of life, during the interchange of action which thus incessantly goes on between physical agents and vital organs, the laws to which inorganic matter is subject are resisted, controlled, and modified. Physical and chemical attractions are brought under the influence of a new and superior agency, with the laws of which we are imperfectly acquainted, but the operation of which we see, and which we call the agency of life. Air, water, heat, electricity, are physical agents, which subvert the most intimate combinations of inorganic bodies, resolving them into their simple elements, and recombining these elements in various modes, and thus forming new bodies, endowed with totally different properties; but the physical and chemical agencies by which these changes are wrought in the inorganic, are resisted, controlled, and modified by the living body: resisted, for these physical agents do not decompose the living body; controlled and modified, for the living body converts these very agents into the material for sustaining its own existence Of all the phenomena included in that circle of actions which we designate by the general term life, this power of resisting the effects universally produced by physical agents on inorganic matter, and of bringing these very agents under subjection to a new order of laws, is one of the most essential and distinctive.

All vital processes are processes of supply, or processes of waste. By every vital action performed by the organized body, some portion of its constituent matter is expended. Numerous vital actions are constantly carried on for the sole purpose of compensating this expenditure. Every moment old particles are carried out of the system; every moment new particles are introduced into it. The matter of which the organized, and more especially the animal, body is composed, is thus in a state of perpetual flux; and in a certain space of time it is completely changed, so that of all the matter that constitutes the animal body at a given point of time, not a single particle remains at another point of time at a given distance.

All the wants of the economy of the plant are satisfied by a due supply of air, water, heat, cold, electricity, and light. Some of these physical agents constitute the crude aliment of the plant; others produce in this aliment a series of changes, by which it is converted from crude aliment into proper nutriment, while others act as stimulants, by which movements are excited, the ultimate object of which is the distribution of the nutriment to the various parts of the economy of the plant.

The same physical agents are indispensable to the support of the animal body; but the animal cannot be sustained by these physical agents alone; for the maintenance of animal life, in some shape or other, vegetable or animal matter, or both in a certain state of combination, must be superadded: hence another distinction between the plant and the animal,—the necessity, on the part of the animal, of an elaborated aliment to maintain its existence. By the vital processes of its economy, the plant converts inorganic into organic matter; by the vital processes of its economy, the animal converts matter, already rendered organic, into its own proper substance. The plant is thus purveyor to the animal: but it is more than purveyor to it; for while it provides, it also prepares its food; it saves the animal one process, that of the transmutation of inorganic into organic matter. The ultimate end, or the final cause of the vital processes performed by the first class of living beings, is thus the elaboration of aliment for the second: the inferior life is spent in ministering, and the great object of its being is to minister to the existence of the superior.

At the point at which organization commences structure is so simple that there is no manifest distinction of organs. Several functions are performed apparently by one single organized substance. The lowest plants and the lowest animals are equally without any separate organs, as far as it is in our power to distinguish them, for carrying on the vital actions they perform. An organized tissue, apparently of an homogeneous nature, containing fluid matter, is all that can be made out by which the most simply-constructed plant carries on its single set, and by which the most simply-constructed animal carries on its double set, of actions. But this simplicity of structure exists only at the very commencement of the organized world. Every advancement in the scale of organization is indicated by the construction of organs manifestly separate for the performance of individual functions; and, invariably, the higher the being, the more complete is this separation of function from function, and, consequently, the greater the multiplication of organs, and the more elaborate and complex the structure;—and hence another distinction between the plant and the animal. The simplicity of the structure of the plant is in striking contrast to the complexity of the structure of the animal; and this difference is not arbitrary; it is a matter of absolute necessity, and the reason of this necessity it will be instructive to contemplate.

The plant, as has been shown, performs only one set of functions, the organic; while the animal performs two sets of functions, the organic and the animal. The animal, then, performs more functions than the plant, and functions of a higher order; it carries on its functions with a greater degree of energy; its functions have a more extended range, and all its functions bear a certain relation to each other, maintaining an harmonious action. The number, the superiority, the relation, the range, and the energy of the functions performed by the animal are, then, so many conditions, which render it absolutely indispensable that it should possess a greater complexity of structure than the plant.

1. To build up structure is to create, to arrange, and to connect organs. Organs are the instruments by which functions are performed, and without the instrument there can be no action. With as many more organs than the plant possesses the animal must, therefore, be provided, as are necessary to carry on the additional functions it performs. Organs, for its organic functions, it must have as well as the plant; but to these must be superadded organs of another class, for which the plant has no need, namely, organs for its animal functions. Two sets of organs must, therefore, be provided for the animal, while the plant requires but one.

2. Some functions performed by the animal are of a higher order than any performed by the plant, and the superior function requires a higher organization. The construction of an organ is complex as its action is elevated; the instrument is elaborately prepared in proportion to the nobleness of its office.

3. But this is not all; for the addition of a superior function requires not only the addition of an organ having a corresponding superiority of structure, but it requires, further, that a certain elevation of structure should be communicated to all the organs of all the inferior functions, on account of the relation which it is necessary to establish between function and function. Unless the organ of an inferior function be constructed with a perfection corresponding to that of the organ of a superior function, the inferior will be incapable of working in harmony with the superior. Take, for example, the inferior function of nutrition: nutrition is an organic function equally necessary to the plant and to the animal, and requiring in both organs for performing it; but this function cannot be performed in the animal by organs as simple as suffice for the plant. Nutrition, in the plant, is carried on in the following mode:—The root of the plant is divided, like the trunk, into numerous branches (fig. I. 1). These branches divide and subdivide into smaller and smaller branches, until at last they reach an extreme degree of minuteness (fig. I. 2 2). The smallest of these divisions, called, from their hair-like tenuity, capillary (fig. I. 2 2), are provided with a peculiar structure, which is endowed with a specific function. In most plants this peculiar structure is found at the terminal point of the rootlet (fig. I. 2 2); but in some plants the capillary branches of the rootlets are provided with distinct bodies (fig. II. 1 2), scarcely to be discerned when the root has been removed some time from the soil, and has become dry (fig. II. 2 2); but which, in a few minutes after the root has been plunged in water, provided the plant be still alive, become turgid with fluid, and, consequently, distinctly visible (fig. II. 1 1 1). These bodies, when they exist, or the terminal point of the rootlet when these bodies are absent, are termed spongeolæ, or spongeoles; and the structure and function of the organ, in both cases, are conceived to be precisely the same. In both the organ consists of a minute cellular structure. Fig. III. 1, shows this structure as it appears when the object is magnified. The office of this organ is to absorb the aliment of the plant from the soil; and so great is its absorbing power, that, as is proved by direct experiment, it absorbs the colouring molecules of liquids, though these molecules will not enter the ordinary pores, which are of much greater magnitude. With the spongeoles are connected vessels which pass through the substance of the stem or trunk to the leaf. Fig. III. 2, shows these tubes springing from the cellular structure of the spongeole, and passing up to the stem or trunk. Fig. IV. 2, exhibits a magnified view of the appearance of the mouths of these tubes on making an horizontal section of the spongeole. Fig. V. 1 1 1, exhibits a view of these tubes passing to the leaf. Figs. VI. and VII. 1 1 1 1, show these vessels spread out upon, and ramifying through, the leaf. The crude aliment, borne by these tubes to the leaf, is there converted into proper nutriment; and from the leaf, when duly elaborated, this proper nutriment is carried out by ducts to the various organs of the plant, in order to supply them with the aliment they need.

Now, for carrying on the process of nutrition in this mode, there must be organs to absorb the crude aliment, organs to convey the crude aliment to the laboratory, the leaf, in which it is converted into proper nutriment; and, finally, organs for carrying out this proper nutriment to the system. Complication of structure, to this extent, is indispensable; and, accordingly, with spongeolæ, with sap-vessels, with leaves, with distributive ducts, the plant is provided. Without all the parts of this apparatus it could not carry on its function: any further complication would be useless.

But, suppose a new and superior function to be added to the plant; suppose it to be endowed with the power of locomotion, what would be the consequence of communicating to it this higher power? That its former state of simplicity would no longer suffice for the inferior function. Why? because the exercise of the superior would interrupt the action of the inferior function. Nutrition by imbibition, and the exercise of locomotion, cannot go on simultaneously in the same being. The plant is fixed in the soil by its roots; and from this, its state of immobility, results this most important consequence, that its spongeolæ are always in contact with its food.

But we may imagine a plant not fixed to the soil; a plant so constituted as to be capable of moving from place to place; such a plant would not be always in contact with its food, and therefore, as it exercised its faculty of locomotion, it could not but interrupt or suspend its function of nutrition. In a being capable of carrying on these two functions simultaneously, the entire apparatus of the function of nutrition must then be modified. Instead of having spongeolæ fixed immovably in the earth, and spread out in a soil adapted to transmit to these organs nutrient matter in a state fitted for absorption, it must be provided with a reservoir for containing its food, in order that it may carry its aliment about with it in all its changes of place. And such is the modification uniformly found in all animals: an internal reservoir for containing its food is provided, perhaps, for every animal without exception. Even the simplest and minutest creatures with which the microscope has made us acquainted, the lowest tribes of the Infusoria (fig. VIII.), the sentient, self-moving cellules, placed at the very bottom of the animal scale, possess this modification of structure. For a long time it was conceived that these minute and simple creatures were without distinction of parts, that they had no separate organs for the reception and digestion of their food; that they absorbed their aliment through the porous tissue of which their body is composed; that thus, instead of having a separate stomach, their entire body is a stomach, and instead of having even as much as a separate organ for absorption, like the more perfect plant, the whole body might be considered as a single spongeole.

But, by a simple and beautiful experiment, a German physiologist has shown the incorrectness of this opinion, and has established the fact, that the distinction between the plant and the animal, here contended for, is found even at the very lowest point of the animal scale. Like other physiologists, conceiving that the difficulty of discovering the structure of the lower tribes of the animalculi might be owing to the transparency or the tissues of which they are composed, it struck Ehrenberg, that if he could feed them with coloured substances, he might obtain some insight into their organization. In his first endeavours to accomplish this object he failed, for he employed the pigments in ordinary use; but either the animals would not touch aliment thus adulterated, or those that did so were instantly killed. It then occurred to him, that these colours are adulterated with lead and other substances, in all probability noxious to the little subjects of his experiment. "What I require," said he, "is some vegetable or animal colouring matter perfectly pure." He then tried perfectly pure indigo and perfectly pure carmine. His success was now complete: in a minute or two, after mixing with their food pure vegetable colouring matter, he observed in the interior of the body of these creatures minute spots of a definite figure, and of the colour of the pigment employed (fig. VIII. 1 1 1 1). The form and magnitude of these spots were different in different tribes, but the same in the same individual, and even in the same species (fig. IX. 1 1, fig. X. 1 1). No other parts of the body were tinged with the colour, though the animals remained in the coloured fluid for days together. This was decisive. This physiologist had now obtained an instrument capable of revealing to him the interior organization of a class of beings, the structure of which had heretofore been wholly unknown. On applying it to the Monas Termo (fig. VIII.), the animated point, or cellule, which stands at the bottom of the animal scale, he discovered, in the posterior portion of its body, several coloured spots which constitute its stomachs (fig. VIII. 1 1 1 1). The different situations and different forms of the stomach in different tribes of these creatures, are represented by the coloured portions (fig. VIII. 1, fig. IX. 1, fig. X. 1), in which the currents of fluid flowing to their mouths are seen (fig. IX. 2, fig. X. 2). These experiments go far towards establishing the fact, that every animal, even the very lowest, has an external mouth and an internal stomach, and that it takes its food by an act of volition.

But if the proof of this must be admitted to be still imperfect with regard to the lowest tribes of animals, it is certain that, as we ascend in the scale of organization, the nutritive apparatus is uniformly arranged in this mode. Every animal of every class large enough to be distinctly visible, and the structure of which is not rendered inappreciable by the transparency of its solids and fluids, is manifestly provided with a distinct internal reservoir for containing its food. On the internal surface of this reservoir open the mouths of vessels, minute in size but countless in number, which absorb the food from the stomach.

Fig. XI. shows these vessels opening on the inner surface of the stomach, the white points representing their mouths, turgid with the food they have absorbed. Fig. XII. exhibits magnified views of the same vessels, the points representing their open mouths, and the lines the vessels themselves in continuation with their mouths. Fig. XIII. shows the appearance of the inner surface of the intestine soon after the animal has taken food; the smaller white lines (1 1 1 1) representing the absorbent vessels full of digested food, and the larger lines (2 2 2 2) the trunks of the absorbent vessels formed by the union of many of the smaller.

From this account, it is clear that the absorbing vessels of the stomach perform an office precisely analogous to that of the spongeoles of the root. What the soil is to the plant, the stomach is to the animal. The absorbing vessels diffused through the stomach, as long as the stomach contains food, are in exactly the same condition as the spongeoles of the root spread out in the soil; and the absorbing vessels of the stomach are as much and as constantly in contact with the aliment, which it is their office to take into the system, as the spongeoles of the root. Such, then, is the expedient adopted to render the function of nutrition compatible with the function of locomotion. A reservoir of food is placed in the interior of the animal, provided with absorbent vessels which are always in contact with the aliment. In this mode, contact with aliment is not disturbed by continual change of place; the organic process is not interrupted by the exercise of the animal function.

But the more elaborate organization which it is necessary to impart to the apparatus of the inferior function, in consequence of the communication of a superior faculty, is not completed simply by the addition of this new organ, the stomach. Other complications are indispensable; for if food be contained in an isolated organ, placed in the interior of the body, means must be provided for conveying the food into this organ; hence the necessity of an apparatus for deglutition. Moreover, the food having been conveyed to the stomach, and having undergone there the requisite changes, means must next be provided for conveying it from the stomach to the other parts of the body; hence the necessity of an apparatus for the circulation. But food, however elaborately prepared by the stomach, is incapable of nourishing the body, until it has been submitted to the action of atmospheric air; hence the necessity of an additional apparatus, either for conveying food to the air, or for transmitting air to the food, or for bringing both the food and the air into contact in the same organ. And, when structure after structure has been built up, in order to carry on this extended series of processes, the number of provisions required is not even yet complete; for of the most nutritious fond the whole mass is not nutritive; and even the whole of that portion of it which is actually applied to the purpose of nutrition, becomes, after a time, worn out, and must be removed from the system; hence the necessity of a further apparatus for excretion.

That nutrition and locomotion may go on together, it is clear, then, that there must be provided a distinct apparatus for containing food, a distinct apparatus for deglutition, a distinct apparatus for circulation, a distinct apparatus for respiration, a distinct apparatus for excretion, and so on; and that, in this manner, the communication of a single function of a superior order renders a modification not merely of one but of many inferior functions absolutely indispensable, in order to adjust the one to the other, and to enable them to act in harmony.

But the necessary complication of structure does not stop even here; for the communication of one function of a superior order imposes the necessity of communicating still another. Locomotion cannot be exercised without perception; sensation is indispensable to volition, and volition, of course, to voluntary motion. A being endowed with the power of moving from place to place, without possessing the power of perceiving external objects, must be speedily destroyed. The communication of sensation to a creature fixed immovably to a single spot, conscious of the approach of bodies, but incapable of avoiding their contact, would be not only useless but pernicious, since it would be to make a costly provision for the production of pain, and nothing else; but the communication of locomotion without sensation would be as unwisely defective, as the former would be perniciously expensive; since it would be to endow a being with a faculty, the exercise of which would be fatal to it for the want of a second faculty to guide the first. Nor could the possession of locomotion, without the further possession of sensation, be otherwise than fatal, for another reason. Consciousness is not necessary to nutrition as performed by the plant, but it is indispensable to nutrition as performed by the animal: for if the food of the animal be not always on the same spot with itself; if it be under the necessity of searching for it, and of conveying it, when found, into the interior of its body, it must, of course, possess the power of perceiving it when within its reach, and of apprehending and appropriating it by an act of volition, of none of which actions is it capable without the possession of sensation. Again, then, we see that, in order to secure harmonious action, function must be put in relation with function. In order to prevent jarring and mutually-destructive action, function must be superadded to function, and throughout the animal creation the complication of structure, which is necessary for the accomplishment of these ends, is given without parsimony, but without profusion: nothing is given which is not needed, nothing is withheld which is required.

4. As we ascend in the scale of organization, numerous functions being carried on, and numerous organs constructed for performing them, it is obvious that the range of each function must be proportionally extended; the range necessarily increasing with the multiplication of organ and function: and this is another cause of the unavoidable complication of structure. Slight consideration will suffice to show the necessary connexion between an extended range of action and complication of structure. Take, as an example, the organic function of respiration: respiration is the function by which air is brought into contact with food; it is the completion of digestion. The sole end of all the apparatus that belongs to this function is to bring the air and the food into a certain degree of proximity. Now, when all the substances that enter into the composition of the body of an animal are slight, delicate, and permeable to air (as in fig. XIV.), and when the body is always surrounded by air, air must at all times be in contact with the particular organ that contains the food, no less than with the general system to which the food is distributed. In this case, to construct a separate apparatus for containing air would be useless, because wherever food is, there air must be, since it constantly permeates every part of the body.

When, on the other hand, the tissues are so firm and dense as to be impermeable; when they are folded into bulky and complex organs, and when these organs are placed in situations to which the external air cannot reach, the construction of a separate apparatus for respiration is indispensable. The respiratory apparatus consists either of organs for carrying air to the food, or of organs for carrying food to the air. The one or the other is adopted, according to the nature of the body. If the size of the animal be small; if the tissues which form the solid portion of its body be delicate in texture; if, at the same time, the wants of its economy require that its food should be highly aërated (for there is the closest connexion between energy of function and perfect aëration of the food), an apparatus of sufficient magnitude to aërate the food in a high degree would occupy the entire bulk of the body. In such a case, it is easier to carry air to the food than food to the air; it is better to make the entire body a respiratory organ, than to construct a respiratory organ disproportioned to the magnitude of the body. Air-tubes diffused through every part of the body, and opening on its external surface, would obviously afford to every point of the system an easy access of air. By an expedient of this kind the system might be highly aërated, while the respiratory apparatus would occupy but a comparatively small space; the function might be performed on an extended scale, while there would be no necessity for encumbering a minute body with a bulky organ. And this is the mode in which respiration is carried on in large tribes of creatures, whose body is small in size and delicate in texture, and the functions of whose economy are performed with energy (fig. XV.).

The Achilles Butterfly of South America (Papilio Achilles),
showing the tracheæ on the upper and under side of the
wings.

But this contrivance will not do when the animal is of large magnitude; when its body is divided into numerous compartments; when these compartments extend far beneath the external surface; when important organs are placed in deeply-seated cavities; and when the substances that compose the organs are dense, hard, thick, and convoluted. To construct air-tubes of the requisite diameter and length, always open, always in a condition to permit the ingress and egress of an adequate current of air to and from the remotest nook and corner of a body such as this, would be difficult, if not impossible. At all events, it is easier, in such a case, to carry the food to the air, than the air to the food. But, for the accomplishment of this purpose, what is necessary? An organ for containing food; an organ for containing air; vessels to carry food to and from the receptacle of the aliment; vessels to carry air to and from the receptacle of the air; expedients to expose a stream of food to a current of air; and, finally, tubes to carry out to the system the product of this complicated operation. Accordingly, a reservoir of food and a reservoir of air; an apparatus by which both are conveyed to their respective receptacles; and an apparatus by which both are brought into contact sufficiently close to admit of their mutual action, are all combined in the lung of the animal, and in the mechanism by which its movements are effected. The object is accomplished, but the apparatus by which it is effected is as complex in structure as it is efficient in action; the result simple; the means by which the result is secured, highly complicated.

And if this be true of an inferior or organic function, it is still more strikingly true of a superior or animal function. The relation is still stricter between the complexity of the apparatus of sensation and the range of feeling, than between the complexity of the apparatus of respiration and the range of the respiratory process. The greater the number of the senses, the greater the number of the organs of sense; the more accurate and varied the impressions conveyed by each, the more complex the structure of the instrument by which they are communicated; the more extended the range of the intellectual operations, the larger the bulk of the brain, the greater the number of its distinct parts, and the more exquisite their organization. From the point of the animal scale, at which the brain first becomes distinctly visible, up to man, the basis of the organ is the same; but, as the range of its function extends, part after part is superadded, and the structure of each part becomes progressively more and more complex. The evidence of this, afforded by comparative anatomy, is irresistible, and the interest connected with the study of it can scarcely be exceeded.

5. In the last place, structure is complex in proportion to the energy of function. The greater the power with which voluntary motion is capable of being exerted, the higher the organization of the apparatus by which it is performed; the more compact and dense the shell, the cartilage, the bone, the firmer the fibre of the muscle, and, in general, the greater its comparative bulk. The wing of the eagle is as much more developed than the wing of the wren, as its flight is higher, and its speed swifter. The muscles which give to the tiger the rapidity and strength of its spring possess a more intense organization than those which slowly move on the tardigrade sloth. The structure of the brain of man is more exquisite than that of the fish, as his perceptions are more acute, and capable of greater combination, comprehension, and continuity.

Thus we see that the organization of the animal is more complex than that of the plant, not from an arbitrary disposition, but from absolute necessity. The few and simple functions performed by the plant require only the few and simple organs with which it is provided: the numerous and complicated functions performed by the animal require its numerous and complicated organs: the plant, simple as it is in structure, is destitute of no organ required by the nature of its economy; the animal, complex as it is in structure, is in possession of no organ which it could dispense with: from the one, nothing is withheld which is needed; to the other, nothing is given which is superfluous: in the one, there is economy without niggardliness; in the other, munificence without waste.

CHAPTER II.

Two distinct lives combined in the animal—Characters of the apparatus of the organic life—Characters of the apparatus of the animal life—Characteristic differences in the action of each—Progress of life—Progress of death.

Of the two sets of functions carried on by living beings, it has been shown, that the plant performs only one, while the animal exercises both. The two lives thus in continual play in the animal differ from each other as much as the process of vegetation differs from that of thought, yet they are united so closely, and act so harmoniously, that their existence as distinct states is not only not apparent to ordinary observation, but the very discovery of the fact is of recent date, and forms one among the splendid triumphs of modern physiology. Their action is perfect, yet their separate identity is so distinctly preserved, that each has its own apparatus and its own action, which are not only not the same, but, in many interesting circumstances, are in striking contrast to each other.

1. In general the organs that belong to the apparatus of the organic life are single, and not symmetrical; the organs that belong to the apparatus of the animal life are either double, or symmetrical, or both. As will be shown hereafter, the heart, the lungs, the stomach, the intestines, the liver, the pancreas, the spleen, the instruments by which the most important functions of the organic life are carried on, are single organs. (Chap. 5.) The figure of each is more or less irregular, so that if a line were carried through their centre, it would not divide them into two equal and precisely corresponding portions. On the contrary, the organs of the animal life are symmetrical. The brain and the spinal cord are divisible into two perfectly equal parts. (Chap. 5.) The nerves which go off from these organs for the most part go off in pairs equal in size and similar in distribution. (Ibid.) The trunk, so important an instrument of voluntary motion, when well formed, is divisible into two perfectly corresponding portions. (Ibid.) The muscular apparatus of one half of the body is the exact counterpart of that of the other; while the arms, the hands, and the lower extremities are not only double, but the organization of the one is precisely similar to that of its fellow.

2. In general, the apparatus of the organic life is placed in the interior of the body, while that of the animal life is placed on the external surface. The organic organs are the instruments by which life is maintained. There is no action of any one of them that can be suspended even for a short space of time without the inevitable extinction of life. But the animal organs are not so much instruments of life as means by which a certain relation is established between the living being and external objects. And this difference in their office is the reason of the difference in their position. Existence depending on the action of the organic organs, they are placed in the interior of the body; they are fixed firmly in their situation in order that they may not be disturbed by the movements of locomotion; they are enveloped in membranes, covered by muscles, placed under the shelter of bones, and every possible care is taken to secure them from accident and to shield them from violence. Existence not being immediately dependent on the action of the organs of the animal life, they do not need to be protected from the contact of external objects with extraordinary care, but it is necessary to the performance of their functions that they should be placed at the exterior of the body. And there they are placed, and so placed as to afford an effectual defence to the organic organs. Thus the groundwork of the animal is made the bulwark of the organic life. The muscles, the immediate agents by which voluntary motion is effected, and the bones, the fixed points and the levers by which that motion acquires the nicest precision and the most prodigious rapidity and power, are so disposed that, while the latter accomplish, in the most perfect manner, their primary and essential office in relation to the muscles, they serve a secondary but scarcely less important office in relation to the internal viscera. As we advance in our subject, we shall see that a beautiful illustration of this is afforded in the structure and action of the trunk; that the trunk is moveable; that it is composed of powerful muscles, and of firm and compact bones; and that while its movements are effected by the action of the muscles which are attached to the bones, these bones enclose a cavity, in which are placed the lungs, the heart, the great trunks of the venous system, the great trunks of the arterial system, and the main trunk of the thoracic duct, the vessel by which the digested aliment is carried into the blood. (Chap. 5.) Thus, by these strong and firm bones, together with the thick and powerful muscles that rest upon them, is formed a secure shelter for a main portion of the apparatus of the organic functions of respiration, circulation, and digestion. The bones and muscles of the thorax, themselves performing an important part in the function of respiration, afford to the lungs the chief organ of this function, composed of tender and delicate tissues, easily injured, and the slightest injury perilling life, a free and secure place to act in. The fragile part of the apparatus is defended by the osseous portion of it, the play of the latter being equally essential to the function as that of the former. In like manner the tender and delicate substance of the brain and spinal cord, the central seat of the animal life, with which all the senses are in intimate communion, is protected by bones and muscles which perform important voluntary movements while the organs of sense which put us in connexion with the external world, which render us susceptible of pleasure, and which give us notice of the approach of objects capable of exciting pain, are placed where external bodies may be brought most conveniently and completely into contact with them; and where alone they can be efficient as the sentinels of the system. For this reason, with the exception of the sense of touch, which, though placed especially at the extremities of the fingers, is also diffused over the whole external surface of the frame, all the senses have their several seats in the head, the most elevated part of the body, of an ovoid figure, capable of moving independently of the rest of the fabric, and which, being supported on a pivot, is enabled to describe at least two-thirds of a circle.

Such is the difference in the structure and position of the apparatus of the two lives, but the difference in their action is still more striking.

1. The action of the apparatus of the organic life when sound is without consciousness; the object of the action of the apparatus of the animal life is the production of consciousness. The final cause of the action of the apparatus of the organic life is the maintenance of existence; the final cause of the action of the apparatus of the animal life is the production of conscious existence. What purpose would be answered by connecting consciousness with the action of the organic organs? Were we sensible of the organic processes; did we know when the heart beats, and the lung plays, and the stomach digests, and the excretory organ excretes, the consciousness could not promote, but might disturb the due and orderly course of these processes. Moreover they would so occupy and engross our minds that we should have little inclination or time to attend to other objects. Beneficently therefore are they placed equally beyond our observation and control. Nevertheless, when our consciousness of these processes may be of service; when they are going wrong; when their too feeble or too intense action is in danger of destroying existence, the animal life is made sensible of what is passing in the organic, in order that the former may take beneficial cognizance of the latter, may do what experience may have taught to be conducive to the restoration of the diseased organ to a sound state, or avoid doing what may conduce to the increase or maintenance of its morbid condition.

But while the action of the organic organs is thus kept alike from our view and feeling, the sole object of the action of the animal organs is to produce and maintain a state of varied and extended consciousness. We do not know when the heart dilates to receive the vital current, nor when it contracts to propel it with renewed impetus through the system; nor when the blood rushes to the lung to give out its useless and noxious particles; nor when the air rushes to the blood to take up those particles, to replace them by others, and thus to purify and renovate the vital fluid. Many processes of this kind are continually going on within us during every moment of our existence, but we are no more conscious of them than we are of the motion of the fluids in the blade of grass on which we tread. On the contrary when an external object produces, in a sentient nerve, that change of state which we denote by the words "an impression;" when the sentient nerve transmits this impression to the brain; when the brain is thereby brought into the state of perception, the animal life is in active operation, and percipient or conscious existence takes place. Consciousness does not belong to the organic, it is the animal life.

2. The functions of the organic life are performed with uninterrupted continuity; to those of the animal life rest is indispensable. The action of the heart is unceasing; it takes not and needs not rest. On it goes, for the space of eighty or ninety years, at the rate of a hundred thousand strokes every twenty-four hours, having at every stroke a great resistance to overcome, yet it continues this action for this length of time without intermission. Alike incessant is the action of the lung, which is always receiving and always emitting air; and the action of the skin, which is always transpiring and always absorbing; and the action of the alimentary canal, which is always compensating the loss which the system is always sustaining.

But of this continuity of action the organs and functions of the animal life are incapable. No voluntary muscle can maintain its action beyond a given time; no effort of the will can keep it in a state of uninterrupted contraction; relaxation must alternate with contraction; and even this alternate action cannot go on long without rest. No organ of sense can continue to receive impression after impression without fatigue. By protracted exertion the ear loses its sensibility to sound, the eye to light, the tongue to savour, and the touch to the qualities of bodies about which it is conversant. The brain cannot carry on its intellectual operations with vigour beyond a certain period; the trains of ideas with which it works become, after a time, indistinct and confused; nor is it capable of reacting with energy until it has remained in a state of rest proportioned to the duration of its preceding activity.

And this rest is sleep. Sleep is the repose of the senses, the rest of the muscles, their support and sustenance. What food is to the organic, sleep is to the animal life. Nutrition can no more go on without aliment, than sensation, thought, and motion without sleep.

But it is the animal life only that sleeps: death would be the consequence of the momentary slumber of the organic. If, when the brain betook itself to repose, the engine that moves the blood ceased to supply it with its vital fluid, never again would it awake. The animal life is active only during a portion of its existence; the activity of the organic life is never for a moment suspended; and in order to endow its organs with the power of continuing this uninterrupted action, they are rendered incapable of fatigue: fatigue, on the contrary, is inseparable from the action of the organs of the animal life; fatigue imposes the necessity of rest, rest is sleep, and sleep is renovation.

3. Between all the functions of the organic life there is a close relation and dependence. Without the circulation there can be no secretion; without secretion, no digestion; without digestion, no nutrition; without nutrition, no new supply of circulating matter, and so through the entire circle. But the functions of the animal life are not thus dependent on each other. One of the circle may be disordered without much disturbance of the rest; and one may cease altogether, while another continues in vigorous action. Sensation may be lost, while motion continues; and the muscle may contract though it cannot feel. One organ of sense may sleep while the rest are awake. One intellectual faculty may be in operation while others slumber. The muscle of volition may act, while there is no consciousness of will. Even the organs of the voice and of progression may perform their office while the sensorium is deeply locked in sleep.

4. The two lives are born at different periods, and the one is in active operation before the other is even in existence. The first action observable in the embryo is a minute pulsating point. It is the young heart propelling its infant stream. Before brain, or nerve, or muscle can be distinguished, the heart is in existence and in action; that is, the apparatus of the organic function of the circulation is built up and is in operation before there is any trace of an animal organ. Arteries and veins circulate blood, capillary vessels receive the vital fluid, and out of it form brain and muscle, the organs of the animal, no less than the various substances that compose the organs of the organic life. The organic is not only anterior to the animal life, but it is by the action of the organic that existence is given to the animal life. The organic life is born at the first moment of existence; the animal life not until a period comparatively distant; the epoch emphatically called the period of birth, namely, the period when the new being is detached from its mother; when it first comes into contact with external objects; when it carries on all the functions of its economy by its own organs, and consequently enjoys independent existence.

5. The functions of the organic life are perfect at once. The heart contracts as well, the arteries secrete as well, the respiratory organs work as well the first moment they begin to act as at any subsequent period. They require no teaching from experience, and they profit nothing from its lessons. On the contrary, the operations of the brain, and the actions of the voluntary muscles, feeble and uncertain at first, acquire strength by slow degrees, and attain their ultimate perfection only at the adult age. How indistinct and confused the first sensations of the infant! Before it acquire accuracy, precision, and truth, how immense the labour spent upon perception! Sensations are succeeded by ideas; sensations and ideas coalesce with sensations and ideas; combinations thus formed suggest other combinations previously formed, and these a third, and the third a fourth, and so is constituted a continuous train of thought. But the infantile associations between sensation and sensation, between idea and idea, and between sensations and ideas, are, to a certain extent, incorrect, and to a still greater extent inadequate; and the misconception necessarily resulting from this early imperfection in the intellectual operations is capable of correction only by subsequent and more extended impressions. During its making hours, a large portion of the time of the infant is spent in receiving impressions which come to it every instant from all directions, and which it stores up in its little treasury; but a large portion is also consumed in the far more serious and difficult business of discrimination and correction. Could any man, after having attained the age of manhood, reverse the order of the course through which he has passed; could he, with the power of observation, together with the experience that belong to manhood, retrace with perfect exactness every step of his sentient existence, from the age of forty to the moment that the air first came into contact with his body at the moment of his leaving his maternal dwelling, among the truths he would learn, the most interesting, if not the most surprising, would be those which relate to the manner in which he dealt with his earliest impressions; with the mode in which he combined them, recalled them, laid them by for future use; made his first general deduction; observed what subsequent experience taught to be conformable, and what not conformable, to this general inference; his emotions on detecting his first errors, and his contrasted feelings on discovering those comprehensive truths, the certainty of which became confirmed by every subsequent impression. Thus to live backwards would be, in fact, to go through the analysis of the intellectual combinations, and, consequently, to obtain a perfect insight into the constitution of the mind; and among the curious results which would then become manifest, perhaps few would appear more surprising than the true action of the senses. The eye, when first impressed by light, does not perceive the objects that reflect it; the ear, when first impressed by sound, does not distinguish the sonorous body. When the operation for cataract has been successfully performed in a person born blind, the eye immediately becomes sensible to light, but the impression of light does not immediately give information relative to the properties of bodies. It is gradually, not instantaneously; it is even by slow degrees that luminous objects are discerned with distinctness and accuracy. To see, to hear, to smell, to taste, to touch, are processes which appear to be performed instantaneously, and which actually are performed with astonishing rapidity in a person who observes them in himself; but they were not always performed thus rapidly: they are processes acquired, businesses learnt; processes and businesses acquired and learnt, not without the cost of many efforts and much labour. But the senses afford merely the materials for the intellectual operations of memory, combination, comparison, discrimination, induction, operations the progress of which is so slow, that they acquire precision, energy, and comprehensiveness only after the culture of years.

And the same is true of the muscles of volition. How many efforts are made before the power of distinct articulation is acquired! how many before the infant can stand! how many before the child can walk! The organic life is born perfect; the animal life becomes perfect only by servitude, and the aptitude which service gives.

6. The organic life may exist after the animal life has perished. The animal life is extinguished when sensation is abolished, and voluntary motion can be performed no more. But disease may abolish sensation and destroy the power of voluntary motion, while circulation, respiration, secretion, excretion, in a word, the entire circle of the organic functions continues to be performed. In a single instant apoplexy may reduce to drivelling fatuity the most exalted intellect, and render powerless and motionless muscles of gigantic strength; while the action of the heart and the involuntary contractions of the muscles may not only not be weakened, but may act with preternatural energy. In a single instant, apoplexy may even completely extinguish the animal life, and yet the organic may go on for hours, days, and even weeks; while catalepsy, perhaps the most singular disease to which the human frame is subject, may wholly abolish sensation and volition, while it may impart to the voluntary muscles the power of contracting with such unnatural energy and continuity, that the head, the trunk, the limbs may become immoveably fixed in whatever attitude they happen to be at the moment the paroxysm comes on. In this extraordinary condition of the nervous system, however long the paroxysm last, and however complete the abolition of consciousness, the heart continues to beat, and the pulse to throb, and the lungs to respire, and all the organic organs to perform their ordinary functions. Dr. Jebb gives the following description of the condition of a young lady who was the subject of this curious malady.

"My patient was seized with an attack just as I was announced. At that moment she was employed in netting; she was in the act of passing the needle through the mesh; in that position she became immoveably rigid, exhibiting, in a pleasing form, a figure of death-like sleep, beyond the power of art to imitate, or the imagination to conceive. Her forehead was serene, her features perfectly composed. The paleness of her colour, and her breathing, which at a distance was scarcely perceptible, operated in rendering the similitude to marble more exact and striking. The position of her fingers, hands, and arms was altered with difficulty, but preserved every form of flexure they acquired: nor were the muscles of the neck exempted from this law, her head maintaining every situation in which the hand could place it, as firmly as her limbs."

In this condition of the system the senses were in a state of profound sleep; the voluntary muscles, on the contrary, were in a state of violent action; but this action not being excited by volition, nor under its control, the patient remained as motionless as she was insensible. The brain was in a state of temporary death; the muscle in a state of intense life. And the converse may happen: the muscle may die, while the brain lives; contractility may be destroyed, while sensibility is perfect; the power of motion may be lost, while that of sensation may remain unaffected. A case is on record, which affords an illustration of this condition of the system. A woman had been for some time confined to her bed, labouring under severe indisposition. On a sudden she was deprived of the power of moving a single muscle of the body; she attempted to speak, but she had no power to articulate; she endeavoured to stretch out her hand, but her muscles refused to obey the commands of her will, yet her consciousness was perfect, and she retained the complete possession of her intellectual faculties. She perceived that her attendants thought her dead, and was conscious of the performance upon her own person of the services usually paid to the dead; she was laid out, her toes were bound together, her chin was tied up; she heard the arrangements for her funeral discussed, and yet she was unable to make the slightest sign that she was still in the possession of sense, feeling, and life.

In one form of disease, then, the animal life, both the sensitive and the motive portions of it, may perish; and in another form of disease, either the one or the other part of it may be suspended, while the organic life continues in full operation: it follows that the two lives, blended as they are, are distinct, since the one is capable of perishing without immediately and inevitably involving the destruction of the other.

7. And, finally, as the organic life is the first born, so it is the last to die; while the animal life, as it is the latest born, and the last to attain its full development, so it is the earliest to decline and the first to perish. In the process of natural death, the extinction of the animal is always anterior to that of the organic life. Real death is a later, and sometimes a much later event than apparent death. An animal appears to be dead when, together with the abolition of sensation and the loss of voluntary motion, respiration, circulation, and the rest of the organic functions can no longer be distinguished; but these functions go on some time after they have ceased to afford external indications of their action. In man, and the warmblooded animals in general, suspension or submersion extinguishes the animal life, at the latest, within the space of four minutes from the time that the atmospheric air is completely excluded from the lung; but did the organic functions also cease at the same period, it would be impossible to restore an animal to life after apparent death from drowning and the like. But however complete and protracted the abolition of the animal functions, re-animation is always possible as long as the organic organs are capable of being restored to their usual vigour. The cessation of the animal life is but the first stage of death, from which recovery is possible; death is complete only when the organic together with the animal functions have wholly ceased, and are incapable of being re-established.

In man, the process of death is seldom altogether natural. It is generally rendered premature by the operation of circumstances which destroy life otherwise than by that progressive and slow decay which is the inevitable result of the action of organized structure. Death, when natural, is the last event of an extended series, of which the first that is appreciable is a change in the animal life and in the noblest portion of that life. The higher faculties fail in the reverse order of their development; the retrogression is the inverse of the progression, and the noblest creature, in returning to the state of non-existence, retraces step by step each successive stage by which it reached the summit of life.

In the advancing series, the animal is superadded to the organic life; sensation, the lowest faculty of the animal life, precedes ratiocination, the highest. The senses called into play at the moment of birth soon acquire the utmost perfection of which they are capable; but the intellectual faculties, later developed, are still later perfected, and the highest the latest.

In the descending series, the animal life fails before the organic, and its nobler powers decay sooner and more rapidly than the subordinate. First of all, the impressions which the organs of sense convey to the brain become less numerous and distinct, and consequently the material on which the mind operates is less abundant and perfect; but at the same time, the power of working vigorously with the material it possesses more than proportionally diminishes. Memory fails; analogous phenomena are less readily and less completely recalled by the presence of those which should suggest the entire train; the connecting links are dimly seen or wholly lost; the train itself is less vivid and less coherent; train succeeds train with preternatural slowness, and the consequence of these growing imperfections is that, at last, induction becomes unsound just as it was in early youth; and for the same reason, namely, because there is not in the mental view an adequate range of individual phenomena; the only difference being that the range comprehended in the view of the old man is too narrow, because that which he had learnt he has forgotten; while in the youth it is too narrow, because that which it is necessary to learn has not been acquired.

And with the diminution of intellectual power the senses continue progressively to fail: the eye grows more dim, the ear more dull, the sense of smell less delicate, the sense of touch less acute, while the sense of taste immediately subservient to the organic function of nutrition is the last to diminish in intensity and correctness, and wholly fails but with the extinction of the life it serves.

But the senses are not the only servants of the brain; the voluntary muscles are so equally; but these ministers to the master-power, no longer kept in active service, the former no longer employed to convey new, varied, and vivid impressions, the latter no longer employed to execute the commands of new, varied, and intense desires, become successively feebler, slower, and more uncertain in their action. The hand trembles, the step totters, and every movement is tardy and unsteady. And thus, by the loss of one intellectual faculty after another, by the obliteration of sense after sense, by the progressive failure of the power of voluntary motion; in a word, by the declining energy and the ultimate extinction of the animal life, man, from the state of maturity, passes a second time through the stage of childhood back to that of infancy; lapses even into the condition of the embryo: what the fœtus was, the man of extreme old age is: when he began to exist, he possessed only organic life; and before he is ripe for the tomb, he returns to the condition of the plant.

And even this merely organic existence cannot be long maintained. Slow may be the waste of the organic organs; but they do waste, and that waste is not repaired, and consequently their functions languish, and no amount of stimulus is capable of invigorating their failing action. The arteries are rigid and cannot nourish; the veins are relaxed and cannot carry on the mass of blood that oppresses them; the lungs, partly choked up by the deposition of adventitious matter, and partly incapable of expanding and collapsing by reason of the feeble action of the respiratory apparatus, imperfectly aërate the small quantity of blood that flows through them; the heart, deprived of its wonted nutriment and stimulus, is unable to contract with the energy requisite to propel the vital current; the various organs, no longer supplied with the quantity and quality of material necessary for carrying on their respective processes, cease to act; the machinery stops, and this is death.

And now the processes of life at an end, the body falls within the dominion of the powers which preside universally over matter; the tie that linked all its parts together, holding them in union and keeping them in action, in direct opposition to those powers dissolved, it feels and obeys the new attractions to which it has become subject; particle after particle that stood in beautiful order fall from their place; the wonderful structures they composed melt away; the very substances of which those structures were built up are resolved into their primitive elements; these elements, set at liberty, enter into new combinations, and become constituent parts of new beings; those new beings in their turn perish; from their death springs life, and so the changes go on in an everlasting circle.

As far as relates to the organized structures in which life has its seat, and to the operations of life dependent on those structures, such is its history; a history not merely curious, but abounding with practical suggestions of the last importance. The usefulness of a familiar acquaintance with the phenomena which have now been elucidated will be apparent at every step as we proceed.

CHAPTER III.

Ultimate object of organization and life—Sources of pleasure—Special provision by which the organic organs influence consciousness and afford pleasure—Point at which the organic organs cease to affect consciousness, and why—The animal appetites: the senses: the intellectual faculties: the selfish and sympathetic affections: the moral faculty—Pleasure the direct, the ordinary, and the gratuitous result of the action of the organs—Pleasure conducive to the development of the organs, and to the continuance of their action—Progress of human knowledge—Progress of human happiness.

The object of structure is the production of function. Of the two functions combined in the living animal, one is wholly subservient to the other. To build up the apparatus of the animal life, and to maintain it in a condition fit for performing its functions, is the sole object of the existence of the organic life. What then is the object of the animal life? That object, whatever it be, must be the ultimate end of organization, and of all the actions of which it is the seat and the instrument.

Two functions, sensation and voluntary motion, are combined in the animal life. Of these two functions, the latter is subservient to the former: voluntary motion is the servant of sensation, and exists only to obey its commands.

Is sensation, then, the ultimate object of organization? Simple sensation cannot be an ultimate object, because it is invariably attended with an ultimate result; for sensation is either pleasurable or painful. Every sensation terminates in a pleasure or a pain. Pleasure or pain, the last event in the series, must then be the final end.

Is the production of pain the ultimate object of organization? That cannot be, for the production of pain is the indirect, not the direct,—the extraordinary, not the ordinary, result of the actions of life. It follows that pleasure must be the ultimate object, for there is no other of which it is possible to conceive. The end of organic existence is animal existence; the end of animal existence is sentient existence; the end of sentient existence is pleasurable existence; the end of life therefore is enjoyment. Life commences with the organic processes; to the organic are superadded the animal; the animal processes terminate in sensation; sensation ends in enjoyment; it follows, that enjoyment is the final end. For this every organ is constructed; to this every action of every organ is subservient; in this every action ultimately terminates.

And without a single exception in the entire range of the sentient creation, the higher the organized structure the greater the enjoyment, mediately or immediately, to which it is subservient. From its most simple to its most complex state, every successive addition to structure, by which function is rendered more elevated and perfect, proportionally increases the exquisiteness of the pleasure to which the function ministers, and in which it terminates.

Pleasure is the result of the action of living organs, whether organic or animal; pleasure is the direct, the ordinary, and the gratuitous result of the action of both sets of organs; the pleasure resulting from the action of the organs is conducive to their complete development, and thereby to the increase of their capacity for affording enjoyment; the pleasure resulting from the action of the organs, and conducive to their development, is equally conducive to the perpetuation of their action, and consequently to the maintenance of life; it follows not only that enjoyment is the end of life, but that it is the means by which life is prolonged. Of the truth of each of these propositions, it will be interesting to contemplate the plenitude of the proof.

1. In the first place, pleasure is the result of the action of the organic organs. It has indeed been shown that the very character by which the action of these organs is distinguished is that they are unattended with consciousness. Nevertheless, by a special provision, consciousness is indirectly connected with the processes of this class, limited in extent indeed, and uniformly terminating at a certain point; but the extent and the limitation alike conducing to the pleasurableness of its nature. And this is an adjustment in the constitution of our frame which is well deserving of attention.

Organic processes are dependent on a peculiar influence derived from that portion of the nervous system distinguished by the term organic. The organic nerves, distributed to the organic organs, take their origin and have their chief seat in the cavities that contain the main instruments of the organic life, namely, the chest and abdomen (see chap. v.). As will be fully shown hereafter, these nerves encompass the great trunks of the blood-vessels that convey arterial blood to the organic organs. In all its ramifications through an organic organ, an arterial vessel is accompanied by its organic nerve; so that wherever the capillary arterial branch goes, secreting or nourishing, there goes, inseparably united with it, an organic nerve, exciting and governing.

Among the peculiarities of this portion of the nervous system, one of the most remarkable is, that it is wholly destitute of feeling. Sensibility is inseparably associated with the idea commonly formed of a nerve. But the nervous system consists of two portions, one presiding over sensation and voluntary motion, hence called the sentient and the motive portions; the other destitute of sensation, but presiding over the organic processes, hence called the organic portion. If the communication between the organic organ and the organic nerve be interrupted, the function of the organ, whatever it be, is arrested. Without its organic nerves, the stomach cannot secrete gastric juice; the consequence is, that the aliment is undigested. Without its organic nerves, the liver cannot secrete bile, the consequence is, that the nutritive part of the aliment is incapable of being separated from its excrementitious portion. The organic organ receives from its organic nerve an influence, without which it cannot perform its function; but the nerve belonging to this class neither feels nor communicates feeling, and hence it imparts no consciousness of the operation of any process dependent upon it. Yet there is not one of these processes that does not exert a most important influence over consciousness. How? By a special provision, as curious in its nature as it is important in its result.

Branches of sentient nerves are transmitted from the animal to the organic system, and from the organic to the animal; and an intimate communication is established between the two classes. The inspection of fig. XVI. will illustrate the mode in which this communication is effected. A B represents a portion of the spinal cord (one of the central masses of the sentient system), covered with its membranes. The part here represented is a front view of that portion of the spinal cord which belongs to the back, and which is technically called the dorsal portion.

1, 2, 3, 4, 5, 6, 7, 8, 9, the second, &c. ribs with the corresponding dorsal (sentient) nerves, a, b, c, d, e, f, g, h, going out to supply their respective organs with sensation.

C D E, a portion of the main trunk of the organic (non-sentient) nerve, commonly called the Great Sympathetic.

F G H, the membrane of the spinal cord cut open and exposing I K, the spinal cord itself, L, the anterior branch of one of the dorsal nerves, arising from the anterior surface of the spinal cord by several bundles of fibres.

M, the posterior branch of the same nerve, arising in like manner from the posterior surface of the spinal cord by several branches of fibres.

The anterior and posterior branches uniting to form one trunk N.

Two branches, P Q, sent off from the spinal (sentient) trunk to unite with the organic (non-sentient) trunk.

R S T U V W, other branches of the sentient, connected with the branches of the non-sentient nervous trunks in the same mode.

X Y, the main trunk of the sympathetic (non-sentient) nerve cut across and turned aside, in order that the parts beneath it (P N) may be more distinctly seen.

From this description, it is apparent that each sentient nerve, before it goes out to the animal organs, to which it is destined to communicate sensation, sends off two branches to the organic or the non-sentient. These sentient nerves mix and mingle with the insensible nerves; accompany them in their course to the organic organs, and ramify with them throughout their substance. It is manifest, then, that sentient nerves, that nerves not necessary to the organic processes, having, as far as is known, nothing whatever to do with those processes, enter as constituent parts into the composition of the organic organs. What is the result? That organic organs are rendered sentient; that organic processes, in their own nature insensible, become capable of affecting consciousness. What follows? What is the consciousness excited? Not a consciousness of the organic process. Of that we still remain wholly insensible. Not simple sensation. The result uniformly produced, as long as the state of the system is that of health, is pleasurable consciousness. The heart sends out to the organs its vital current. Each organ, abstracting from the stream the particles it needs, converts them into the peculiar fluid or solid it is its office to form. The stomach, from the arterial streamlets circulating through it, secretes gastric juice; the liver, from the venous streamlets circulating through it, secretes bile. When these digestive organs have duly prepared their respective fluids, they employ them in the elaboration of the aliment. We are not conscious of this elaboration, though it go on within us every moment; but is consciousness not affected by the process? Most materially. Why? Because sentient mingle with organic nerves; because the sentient nerves are impressed by the actions of the organic organs. And how impressed? As long as the actions of the organic organs are sound, that is, as long as their processes are duly performed, the impression communicated to the sentient nerves is in its nature agreeable; is, in fact, THE PLEASURABLE CONSCIOUSNESS WHICH CONSTITUTES THE FEELING OF HEALTH. The state of health is nothing but the result of the due performance of the organic organs: it follows that the feeling of health, the feeling which is ranked by every one among the most pleasurable of existence, is the result of the action of organs of whose direct operations we are unconscious. But the pleasurable consciousness thus indirectly excited is really the consequence of a special provision, established for the express purpose of producing pleasure. Processes, in their own nature insensible, are rendered sentient expressly for this purpose, that, over and above the special object they serve, they may afford enjoyment. In this case, the production of pleasure is not only altogether gratuitous, not only communicated for its own sake, not only rested in as an ultimate object, but it is made to commence at the very confines of life; it is interwoven with the thread of existence: it is secured in and by the actions that build up and that support the very framework, the material instrument of our being.

But if the communication of sensibility to processes in their own nature incapable of exciting feeling, for the purpose of converting them into sources of pleasurable consciousness, indicate an express provision for the production of enjoyment, that provision is no less exemplified in the point at which this superadded sensibility is made to cease.

Some of the consequences of a direct communication of consciousness to an organic process have been already adverted to. Had the eye, besides transmitting rays of light to the optic nerve, been rendered sensible of the successive passage of each ray through its substance, the impression excited by luminous bodies, which is indispensable to vision, the ultimate object of the instrument, if not wholly lost, must necessarily have become obscure, in direct proportion to the acuteness of this sensibility. The hand of the musician could scarcely have executed its varied and rapid movements upon his instrument, had his mind been occupied at one and the same instant with the process of muscular contraction in the finger, and the idea of music in the brain. Had the communication of such a twofold consciousness been possible, in no respect would it have been beneficial, in many it would have been highly pernicious; and the least of the evils resulting from it would have been, that the inferior would have interrupted the superior faculty, and the means deteriorated the end. But in some cases the evil would have been of a much more serious nature. Had we been rendered sensible of the flow of the vital current through the engine that propels it; were the distension of the delicate valves that direct the current ever present to our view; by some inward feeling were we reminded, minute by minute, of the progress of the aliment through the digestive apparatus, and were the mysterious operations of the organic nerves palpable to sight, the terror of the maniac, who conceived that his body was composed of unannealed glass, would be the ordinary feeling of life. Every movement would be a matter of anxious deliberation; and the approach of every body to our own would fill us with dismay. But adjusted as our consciousness actually is, invariably the point at which the organic process begins is that at which sensation ends. Had sensation been extended beyond this point, it would have been productive of pain: at this point it uniformly stops. Nevertheless, by the indirect connexion of sensation with the organic processes, a vast amount of pleasure might be created: a special apparatus is constructed for the express purpose of establishing the communication. There is thus the twofold proof, the positive and the negative, the evidence arising as well from what they do, as from what they abstain from doing, that the organic processes are, and are intended to be, sources of enjoyment.

But the production of pleasure, commencing at this the lowest point of conscious existence, increases with the progressive advancement of organization and function.

The appetite for food, and the voluntary actions dependent upon it, may be considered as the first advancement beyond a process purely organic. The function by which new matter is introduced into the system and converted into nutriment, is partly an animal and partly an organic operation. The animal part of it consists of the sensations of hunger and thirst, by which we are taught when the wants of the system require a fresh supply of aliment, together with the voluntary actions by which the aliment is introduced into the system. The organic part of the function consists of the changes which the aliment undergoes after its introduction into the system, by which it is converted into nutriment. Sensations always of a pleasurable nature arise indirectly in the manner already explained, from the due performance of the organic part of the function; but pleasure is also directly produced by the performance of the animal part of it. Wholesome food is grateful; the satisfaction of the appetite for food is pleasurable. Food is necessary to the support of life; but it is not indispensable to the maintenance of life that food should be agreeable. Appetite there must be, that food may be eaten; but the act of eating might have been secured without connecting it with pleasure. Pleasure, however, is connected with it, first directly, by the gratefulness of food, and secondly indirectly, by the due digestion of the food. And the annexation of pleasure in this twofold mode to the performance of the function of nutrition is another case of the gratuitous bestowment of pleasure; another instance in which pleasure is communicated for its own sake, and rested in as an ultimate object. Pleasures of this class are sometimes called low; they are comparatively low; but they are not the less pleasures, because they are exceeded in value by pleasures of a nobler nature. Man may regard them with comparative indifference, because he is endowed with faculties which afford him gratifications superior in kind and larger in amount; but it is no mark of wisdom to despise and neglect even these: for they are annexed to the exercise of a function which is the first to exalt us above a merely organic existence; they are the first pleasures of which, considered merely as sentient creatures, we are susceptible; they amount in the aggregate to an immense sum; and they mark the depth in our nature in which are laid the fountains of enjoyment.

Organs of sense, intellectual faculties, social affections, moral powers, are superadded endowments of a successively higher order: at the same time, they are the instruments of enjoyment of a nature progressively more and more exquisite.

An organ of sense is an instrument composed of a peculiar arrangement of organized matter, by which it is adapted to receive from specific agents definite impressions. Between the agent that produces and the organ that receives the impression, the adaptation is such, that the result of their mutual action is, in the first place, the production of sensation, and, in the second place, the production of pleasure. The pleasure is as much the result as the sensation. This is true of the eye in seeing, the ear in hearing, the hand in touching, the organ of smell in smelling, and the tongue in tasting. Pleasure is linked with the sense; but there might have been the sense without the pleasure. A slight difference in the construction of the organ, or in the intensity of the agent, would not merely have changed, it would even have reversed the result; would have rendered the habitual condition of the eye, the ear, the skin, not such as it now is in health, but such as it is in the state of inflammation. But the adjustment is such as habitually to secure that condition of the system in which every action that excites sensation produces pleasure as its ordinary concomitant; and the amount of enjoyment which is thus secured to every man, and which every man without exception actually experiences in the ordinary course of an ordinary life, it would be beyond his power to estimate were he always sensible of the boon; but the calculation is altogether impossible, when, as is generally the case, he merely enjoys without ever thinking of the provisions which enable him to do so.

But if the pleasures that arise from the ordinary operations of sense form, in the aggregate, an incalculable sum, how great is the accession brought to this stock by the endowments next in order in the ascending scale, namely, the intellectual faculties!

There is one effect resulting from the operation of the intellectual faculties on the senses that deserves particular attention. The higher faculties elevate the subordinate in such a manner as to make them altogether new endowments. In illustration of this, it will suffice to notice the change wrought, as if in the very nature of sensation, the moment it becomes combined with an intellectual operation, as exemplified in the difference between the intellectual conception of beauty, and the mere perception of sense. The grouping of the hills that bound that magnificent valley which I behold at this moment spread out before my view; the shadow of the trees at the base of some of them, stretching its deep and varied outline up the sides of others; the glancing light now brightening a hundred different hues of green on the broad meadows, and now dancing on the upland fallows; the ever-moving, ever-changing clouds; the scented air; the song of birds; the still more touching music which the breeze awakens in the scarcely trembling branches of those pine trees,—the elements of which this scene is composed, the mere objects of sense, the sun, the sky, the air, the hills, the woods, and the sounds poured out from them, impress the senses of the animals that graze in the midst of them; but on their senses they fall dull and without effect, exciting no perception of their loveliness, and giving no taste of the pleasures they are capable of affording. Nor even in the human being, whose intellectual faculties have been uncultivated, do they awaken either emotions or ideas; the clown sees them, hears them, feels them no more than the herds he tends: yet in him whose mind has been cultivated and unfolded, how numerous and varied the impressions, how manifold the combinations, how exquisite the pleasures produced by objects such as these!

And from the more purely intellectual operations, from memory, comparison, analysis, combination, classification, induction, how still nobler the pleasure! Not to speak of the happiness of him who, by his study of natural phenomena, at length arrived at the stupendous discovery that the earth and all the stars of the firmament move, and that the feather falls to the ground, by the operation of one and the same physical law; nor of the happiness of him who sent his kite into the cloud, and brought down from its quiet bed the lightning which he suspected was slumbering there; nor of the happiness of him who concentrated, directed, and controlled that mighty power which has enabled the feeble hand of man to accomplish works greater than have been feigned of fabled giant; which has annihilated distance; created, by economizing time; changed in the short space in which it has been in operation the surface of the habitable globe; and is destined to work upon it more and greater changes than have been effected by all other causes combined; nor of the happiness of him who devoted a longer life with equal success to a nobler labour, that of REARING THE FABRIC OF FELICITY BY THE HAND OF REASON AND OF LAW. The intellectual pleasures of such men as Newton, Franklin, Watt, and Bentham, can be equalled only by those who possess equal intellectual power, and who put forth equal intellectual energy: to be greatly happy as they were, it were necessary to be as highly endowed; but to be happy, it is not necessary to be so endowed. In the ordinary intellectual operations of ordinary men, in their ordinary occupations, there is happiness. Every human being whose moments have passed with winged speed, whose day has been short, whose year is gone almost as soon as it seemed commenced, has derived from the exercise of his intellectual faculties pleasures countless in number and inestimable in value.

But the sympathetic pleasures, out of which grow the social, are of a still higher order even than the intellectual. The pleasures that result from the action of the organic organs, from the exercise of the several senses, and from the operation of the intellectual faculties, like the sensations in which they arise, belong exclusively to the individual being that experiences them, and cannot be communicated to another. Similar sensations and pleasures may be felt by beings similarly constituted; but the actual sensations and pleasures afforded by the exercise of a person's own organs and faculties are no more capable of becoming another's than his existence. These, then, are strictly the selfish pleasures; and the provision that has been made for securing them has been shown.

But there are pleasures of another class, pleasures having no relation whatever to a person's own sensation or happiness; pleasures springing from the perception of the enjoyment of others. The sight of pleasure not its own affects the human heart, provided its state of feeling be natural and sound, just as it would be affected were it its own. Not more real is the pleasure arising from the gratification of appetite, the exercise of sense, and the operation of intellect, than that arising from the consciousness that another sentient being is happy. Pleasures of this class are called sympathetic, in contradistinction to those of the former class, which are termed selfish.

There are then two principles in continual operation in the human being, the selfish and the sympathetic. The selfish is productive of pleasure of a certain kind; the sympathetic is productive of pleasure of another kind. The selfish is primary and essential; the sympathetic, arising out of the selfish, is superadded to it. And so precisely what the animal life is to the organic, the sympathetic principle is to the selfish; and just what the organic life gains by its union with the animal, the mental constitution gains by the addition of the sympathetic to the selfish affection. The analogy between the combination in both cases is in every respect complete. As the organic life produces and sustains the animal, so the sympathetic principle is produced and sustained by the selfish. As the organic life is conservative of the entire organization of the body, so the selfish principle is conservative of the entire being. As the animal life is superadded to the organic, extending, exalting, and perfecting it, so the sympathetic principle is superadded to the selfish, equally extending, exalting, and perfecting it. The animal life is nobler than the organic, whence the organic is subservient to the animal; but there is not only no opposition, hostility, or antagonism between them, but the strictest possible connexion, dependence, and subservience. The sympathetic principle is nobler than the selfish, whence the selfish is subservient to the sympathetic; but there is not only no opposition, hostility, or antagonism between them, but the strictest possible connexion, dependence, and subservience. Whatever is conducive to the perfection of the organic, is equally conducive to the perfection of the animal life; and whatever is conducive to the attainment of the true end of the selfish is equally conducive to the attainment of the true end of the sympathetic principle. The perfection of the animal life cannot be promoted at the expense of the organic, nor that of the organic at the expense of the animal; neither can the ultimate end of the selfish principle be secured by the sacrifice of the sympathetic, nor that of the sympathetic by the sacrifice of the selfish. Any attempt to exalt the animal life beyond what is compatible with the healthy state of the organic, instead of accomplishing that end, only produces bodily disease. Any attempt to extend the selfish principle beyond what is compatible with the perfection of the sympathetic, or the sympathetic beyond what is compatible with the perfection of the selfish, instead of accomplishing the end in view, only produces mental disease. Opposing and jarring actions, antagonizing and mutually destructive powers, are combined in no other work of nature; and it would be wonderful indeed were the only instance of it found in man, the noblest of her works, and in the mind of man, the noblest part of her noblest work.

No one supposes that there is any such inharmonious combination in the organization of his physical frame, and the notion that it exists in his mental constitution, as it is founded in the grossest ignorance, so it is productive of incalculable mischief. In both, indeed, are manifest two great powers, each distinct; each having its own peculiar operation; and the one being subservient to the other, but both conducing alike to one common end. By the addition of the apparatus of the animal to that of the organic life, a nobler structure is built up than could have been framed by the organic alone: by the addition of the sympathetic to the selfish part of the mental constitution, a happier being is formed than could have been produced by the selfish alone. And as the organic might have existed without the animal life, but by the addition of the animal a new and superior being is formed, so might the selfish part of the mental constitution, and the pleasures that flow from it, have existed alone; but by the addition of the sympathetic, a sum is added to enjoyment, of the amount of which some conception may be formed by considering what human life would be, with every selfish appetite and faculty gratified in the fullest conceivable degree, but without any admixture whatever of sympathetic or social pleasure. Selfish enjoyment is not common. If any one set himself to examine what at first view might seem a purely selfish pleasure, he will soon be sensible that, of the elements composing any given state of mind to which he would be willing to affix the term pleasurable, a vast preponderance consists of sympathetic associations. The more accurately he examine, and the farther he carry his analysis, the stronger will become his conviction, that a purely selfish enjoyment, that is, a truly pleasurable state of mind, in no degree, mediately or immediately, connected with the pleasurable state of another mind, is exceedingly rare.

But if the constitution of human nature and the structure of human society alike render it difficult for the human heart to be affected with a pleasure in no degree derived from—absolutely and totally unconnected with sympathetic association, of that complex pleasure which arises out of social intercourse, partly selfish and partly sympathetic, how far sweeter the sympathetic than the selfish part; and as the sympathetic preponderates over the selfish, how vast the increase of the pleasure! And when matured, exalted into affection—affection, that holy emotion which exerts a transforming influence over the selfish part of human nature, turning it into the sympathetic; affection, which renders the happiness of the beloved object inexpressibly dearer to the heart than its own; affection, among the benignant feelings of which as there is none sweeter so there is none stronger than that of self-devotion, nay, sometimes even of self-sacrifice; affection, which is sympathy pure, concentrated, intense—Oh how beautiful is the constitution of this part of our nature, by which the most transporting pleasures the heart receives are the direct reflection of those it gives!

Nor ought it to be overlooked, that, while nearly all the selfish, like all the sensual pleasures, cannot be increased beyond a fixed limit, cannot be protracted beyond a given time, are short-lived in proportion as they are intense, and satiate the appetite they gratify, the sympathetic pleasures are capable of indefinite augmentation; are absolutely inexhaustible; no limit can be set to their number, and no bound to their growth; they excite the appetite they gratify; they multiply with and by participation, and the more is taken from the fountain from which they flow, the deeper, the broader, and the fuller the fountain itself becomes.

But not only is the mental state of affection in all its forms and degrees highly pleasurable, but the very consciousness of being the object of affection is another pleasure perfectly distinct from that arising immediately from the affection itself. It has been said of charity, that it is twice blessed, that it blesses alike him that gives and him that receives; but love has in it a threefold blessing: first, in the mental state itself; secondly, in the like mental state which the manifestation of it produces in another; and thirdly, in the mental state inseparable from the consciousness of being the object of affection. And this reflex happiness, this happiness arising from the consciousness of being the object, is even sweeter than any connected with being the subject of affection.

In like manner there is pleasure in the performance of beneficent actions; in energetic, constant, and therefore ultimately successful exertions to advance the great interests of human kind, in art, in science, in philosophy, in education, in morals, in legislation, in government; whether those exertions are put forth in the study, the school, the senate, or any less observed though perhaps not less arduous nor less important field of labour. Exertions of this kind beget in those for whom, towards those by whom, they are made, benignant feelings—respect, veneration, gratitude, love. With such feelings the philosopher, the instructor, the legislator, the statesman, the philanthropist, knows that he is, or that, sooner or later, he will be regarded by his fellow men; and in this consciousness there is happiness: but this is another source of happiness perfectly distinct from that arising from the performance of beneficent actions; it is a new happiness superadded to the former, and, if possible, still more exquisite. Thus manifold is the beneficent operation of the sympathetic affection: thus admirable is the provision made in the constitution of our nature for the excitement and extension of this affection, and, through its instrumentality, for the multiplication and exaltation of enjoyment!

In affections and actions of the class just referred to, and in the pleasures that result from them, there is much of the nature which is commonly termed moral. And the power to which the moral affections and actions are referred is usually and justly considered as the supreme faculty of the mind; for it is the regulator and guide of all the others; it is that by which they attain their proper and ultimate object. Of whatever pleasure human nature is capable in sensation, in idea, in appetite, in passion, in emotion, in affection, in action; whatever is productive of real pleasure, in contradistinction to what only cheats with the false hope of pleasure; whatever is productive of pure pleasure, in contradistinction to what is productive partly of pleasure and partly of pain, and consequently productive not of pure, but of mixed pleasure; whatever is productive of a great degree of pleasure in contradistinction to what is productive of a small degree of pleasure; whatever is productive of lasting pleasure, in contradistinction to what is productive of temporary pleasure; whatever is productive of ultimate pleasure, in contradistinction to what is productive of immediate pleasure, but ultimate pain; this greatest and most perfect pleasure it is the part of the moral faculty to discover. In the degree in which the operation of this faculty is correct and complete, it enables the human being to derive from every faculty of his nature the greatest, the purest, the most enduring pleasure; that is, the maximum of felicity. This is the proper scope and aim of the moral faculty; to this its right exercise is uniformly conducive; and this, as it is better cultivated and directed, it will accomplish in a higher degree, in a continual progression, to which no limit can be assigned. But if the operation of this faculty be to render every other in the highest degree conducive to happiness, conformity to the course of conduct required by it, must of course be that highest happiness. Conformity to the course of conduct pointed out by the moral faculty as conducive in the highest degree to happiness is moral excellence, or, in the definite and exact sense of the word, virtue. And in this sense it is that virtue is happiness. It is because it discriminates the true sources of happiness, that is, directs every other faculty into its proper course, and guides it in that course to the attainment of its ultimate object, that the moral faculty is ranked as the highest faculty of the mind. Supposing the operation of this faculty to be perfect, it is but an identical expression to say, that to follow its guidance implicitly is to follow the road that leads to the most perfect happiness. But, over and above the happiness thus directly and necessarily resulting from yielding uniform and implicit obedience to the moral faculty, there is, in the very consciousness of such conformity, a new happiness, as pure as it is exalted. Thus, in a twofold manner, is the moral the highest faculty of the mind, the source of its highest happiness; and thus manifest it is, from every view that can be taken of the constitution of human nature, that every faculty with which it is endowed, from the highest to the lowest, not only affords its own proper and peculiar pleasure, but that each, as it successively rises in the scale, is proportionately the source of a nobler kind, and a larger amount of enjoyment.

And the pleasure afforded by the various faculties with which the human being is endowed is the immediate and direct result of their exercise. With the exception of the organic organs, and the reason for the exception in regard to them has been assigned, the action of the organs is directly pleasurable. From the exercise of the organs of sense, from the operation of the intellectual faculties, from appetite, passion, and affection, pleasure flows as directly as the object for which the instrument is expressly framed.

And pleasure is the ordinary result of the action of the organs; pain is sometimes the result, but it is the extraordinary not the ordinary result. Whatever may be the degree of pain occasionally produced, or however protracted its duration, yet it is never the natural, that is, the usual or permanent state, either of a single organ, or of an apparatus, or of the system. The usual, the permanent, the natural condition of each organ, and of the entire system, is pleasurable. Abstracting, therefore, from the aggregate amount of pleasure, the aggregate amount of pain, the balance in favour of pleasure is immense. This is true of the ordinary experience of ordinary men, even taking their physical and mental states such as they are at present; but the ordinary physical and mental states, considered as sources of pleasure of every human being, might be prodigiously improved; and some attempt will be made, in a subsequent part of this work, to show in what manner and to what extent.

It has been already stated that there are cases in which pleasure is manifestly given for its own sake; in which it is rested in as an ultimate object: but the converse is never found: in no case is the excitement of pain gratuitous. Among all the examples of secretion, there is no instance of a fluid, the object of which is to irritate and inflame: among all the actions of the economy, there is none, the object of which is the production of pain.

Moreover, all such action of the organs, as is productive of pleasure, is conducive to their complete development, and consequently to the increase of their capacity for producing pleasure; while all such action of the organs as is productive of pain is preventive of their complete development, and consequently diminishes their capacity for producing pain. The natural tendency of pleasure is to its own augmentation and perpetuity. Pain, on the contrary, is self-destructive.

Special provision is made in the economy, for preventing pain from passing beyond a certain limit, and from enduring beyond a certain time. Pain, when it reaches a certain intensity, deadens the sensibility of the sentient nerve; and when it lasts beyond a certain time, it excites new actions in the organ affected, by which the organ is either restored to a sound state, or so changed in structure that its function is wholly abolished. But change of structure and abolition of function, if extensive and permanent, are incompatible with the continuance of life. If, then, the actions of the economy, excited by pain, fail to put an end to suffering by restoring the diseased organ to a healthy state, they succeed in putting an end to it by terminating life. Pain, therefore, cannot be so severe and lasting as materially to preponderate over pleasure, without soon proving destructive to life.

But the very reverse is the case with pleasure. All such action of the organs as is productive of pleasure is conducive to the perpetuation of life. There is a close connexion between happiness and longevity. Enjoyment is not only the end of life, but it is the only condition of life which is compatible with a protracted term of existence. The happier a human being is, the longer he lives; the more he suffers, the sooner he dies; to add to enjoyment, is to lengthen life; to inflict pain, is to shorten the duration of existence. As there is a point of wretchedness beyond which life is not desirable, so there is a point beyond which it is not maintainable. The man who has reached an advanced age cannot have been, upon the whole, an unhappy being; for the infirmity and suffering which embitter life cut it short. Every document by which the rate of mortality among large numbers of human beings can be correctly ascertained contains in it irresistible evidence of this truth. In every country, the average duration of life, whether for the whole people or for particular classes, is invariably in the direct ratio of their means of felicity; while, on the other hand, the number of years which large portions of the population survive beyond the adult age may be taken as a certain test of the happiness of the community. How clear must have been the perception of this in the mind of the Jewish legislator when he made the promise, that thy days may be long in the land which the Lord thy God hath given thee—the sanction of every religious observance, and the motive to every moral duty!

Deeply then are laid the fountains of happiness in the constitution of human nature. They spring from the depths of man's physical organization; and from the wider range of his mental constitution they flow in streams magnificent and glorious. It is conceivable that from the first to the last moment of his existence, every human being might drink of them to the full extent of his capacity. Why does he not? The answer will be found in that to the following question. What must happen before this be possible? The attainment of clear and just conceptions on subjects, in relation to which the knowledge hitherto acquired by the most enlightened men is imperfect. Physical nature, every department of it, at least, which is capable of influencing human existence and human sensation; human nature, both the physical and the mental part of it; institutions so adapted to that nature as to be capable of securing to every individual, and to the whole community, the maximum of happiness with the minimum of suffering—this must be known. But knowledge of this kind is of slow growth. To expect the possession of it on the part of any man in such a stage of civilization as the present, is to suppose a phenomenon to which there is nothing analogous in the history of the human mind. The human mind is equally incapable of making a violent discovery in any department of knowledge, and of taking a violent bound in any path of improvement. What we call discoveries and improvements are clear, decided, but for the most part gentle, steps in advancement of the actual and immediately-preceding state of knowledge. The human mind unravels the great chain of knowledge, link by link; when it is no longer able to trace the connecting link, it is at a stand; the discoverer, in common with his contemporaries, seeing the last ascertained link, and from that led on by analogies which are not perceived by, or which do not impress, others, at length descries the next in succession; this brings into view new analogies, and so prepares the way for the discernment of another link; this again elicits other analogies which lead to the detection of other links, and so the chain is lengthened. And no link, once made out, is lost.

Chemists tell us that the adjustment of the component elements of water is such, that although they readily admit of separation and are subservient to their most important uses in the economy of nature by this very facility of decomposition, yet that their tendency to recombination is equal, so that the quantity of water actually existing at this present moment in the globe is just the same as on the first day of the creation, neither the operations of nature, nor the purposes to which it has been applied by man, having used up, in the sense of destroying, a single particle of it. Alike indestructible are the separate truths that make up the great mass of human knowledge. In their ready divisibility and their manifold applications, some of them may sometimes seem to be lost; but if they disappear, it is only to enter into new combinations, many of which themselves become new truths, and so ultimately extend the boundaries of knowledge. Whatever may have been the case in time past, when the loss of an important truth, satisfactorily and practically established, may be supposed possible, such an event is inconceivable now when the art of printing at once multiplies a thousand records of it, and, with astonishing rapidity, makes it part and parcel of hundreds of thousands of minds. A thought more full of encouragement to those who labour for the improvement of their fellow beings there cannot be. No onward step is lost; no onward step is final; every such step facilitates and secures another. The savage state, that state in which gross selfishness seeks its object simply and directly by violence, is past. The semi-savage or barbarous state, in which the grossness of the selfishness is somewhat abated, and the violence by which it seeks its object in some degree mitigated, by the higher faculties and the gentler affections of our nature, but in which war still predominates, is also past. To this has succeeded the state in which we are at present, the so-called civilized state—a state in which the selfish principle still predominates, in which the justifiableness of seeking the accomplishment of selfish purposes by means of violence, that of war among the rest, is still recognized, but in which violence is not the ordinary instrument employed by selfishness, its ends being commonly accomplished by the more silent, steady, and permanent operation of institutions. This state, like the preceding, will pass away. How soon, in what precise mode, by what immediate agency, none can tell. But we are already in possession of the principle which will destroy the present and introduce a better social condition, namely, the principle at the basis of the social union, THE MAXIMUM OF THE AGGREGATE OF HAPPINESS; THE MAXIMUM OF THE AGGREGATE OF HAPPINESS SOUGHT BY THE PROMOTION OF THE MAXIMUM OF INDIVIDUAL HAPPINESS!

CHAPTER IV.

Relation between the physical condition and happiness, and between happiness and longevity—Longevity a good, and why—Epochs of life—The age of maturity the only one that admits of extension—Proof of this from physiology—Proof from statistics—Explanation of terms—Life a fluctuating quantity—Amount of it possessed in ancient Rome: in modern Europe: at present in England among the mass of the people and among the higher classes.

Life depends on the action of the organic organs. The action of the organic organs depends on certain physical agents. As each organic organ is duly supplied with the physical agent by which it carries on its respective process, and as it duly appropriates what it receives, the perfection of the physical condition is attained; and, according to the perfection or imperfection of the physical condition, supposing no accident interrupt its regular course, is the length or the brevity of life.

It is conceivable that the physical condition might be brought to a high degree of perfection, the mind remaining in a state but little fitted for enjoyment; because it is necessary to enjoyment that there be a certain development, occupation, and direction of the mental powers and affections: and the mental state may be neglected, while attention is paid to the physical processes. But the converse is not possible. The mental energies cannot be fully called forth while the physical condition is neglected. Happiness presupposes a certain degree of excellence in the physical condition; and unless the physical condition be brought to a high degree of excellence, there can be no such development, occupation, and direction of the mental powers and affections as is requisite to a high degree of enjoyment.

That state of the system in which the physical condition is sound is in itself conducive to enjoyment; while a permanent state of enjoyment is in its turn conducive to the soundness of the physical condition. It is impossible to maintain the physical processes in a natural and vigorous condition if the mind be in a state of suffering. The bills of mortality contain no column exhibiting the number of persons who perish annually from bodily disease, produced by mental suffering; but every one must occasionally have seen appalling examples of the fact. Every one must have observed the altered appearance of persons who have sustained calamity. A misfortune, that struck to the heart, happened to a person a year ago; observe him some time afterwards; he is wasted, worn, the miserable shadow of himself; inquire about him at the distance of a few months, he is no more.

It is stated by M. Villermé, that the ordinary rate of mortality in the prisons of France, taking all together, is one in twenty-three—a rate which corresponds to the age of sixty-five in the common course of life. But in the vast majority of cases the unfortunate victims of the law are no older than from twenty-five to forty-five years of age. Taking them at the mean age of thirty-five, it follows that the suffering from imprisonment, and from the causes that lead to it, is equivalent to thirty years wear and tear of life. But this is not all; for it is found that, during imprisonment, the ordinary chances of death are exactly quadrupled.

In regard to the whole population of a country, indigence may be assumed to be a fair measure of unhappiness, and wealth of happiness. If the rate of mortality in the indigent class be compared with that of the wealthy, according to M. Villermé, it will be found in some cases to be just double. Thus it is affirmed that, in some cases in France, taking equal numbers, where there are one hundred deaths in a poor arrondissement, there are only fifty in a rich; and that taking together the whole of the French population, human life is protracted twelve years and a half among the wealthy beyond its duration among the poor: consequently, in the one class, a child, newly born, has a probability of living forty-two and a half years; in the other only thirty years.

In the great life-insurance establishments in England, a vast proportion of the persons who insure their lives are persons compelled to do so by their creditors; while three-fourths of those who voluntarily insure their lives are professional men, living in great towns, and experiencing the anxieties and fatigues, the hopes and disappointments of professional life. In one of these establishments in London, out of 330 deaths that happened in twenty-six years preceding the year 1831, it was found that eleven died by suicide, being one in thirty, implying the existence of an appalling amount of mental suffering. The number of persons belonging to an insurance office who perish by suicide is sure to be accurately known, death by suicide rendering the policy void. It would be most erroneous to suppose that these persons put an end to their existence under the mere influence of the mental states of disappointment and despondency. The mind reacted upon the body: produced physical disease, probably inflammation of the brain, and under the excitement of this physical disease, the acts of suicide were committed. More than one case has come to my knowledge in which inflammation of the brain having been excited by mental suffering, suicide was committed by cutting the throat. During the flow of blood, which was gradual, the brain was relieved; the mind became perfectly rational; and the patient might have been saved had a surgeon been upon the spot, or had the persons about the patient known where and how to apply the pressure of the finger to staunch the flow of blood, until surgical aid could be procured.

By a certain amount and intensity of misery life may be suddenly destroyed; by a smaller amount and intensity, it may be slowly worn out and exhausted. The state of the mind affects the physical condition; but the continuance of life is wholly dependent on the physical condition: it follows that in the degree in which the state of the mind is capable of affecting the physical condition, it is capable of influencing the duration of life.

Were the physical condition always perfect, and the mental state always that of enjoyment, the duration of life would always be extended to the utmost limit compatible with that of the organization of the body. But as this fortunate concurrence seldom or never happens, human life seldom or never numbers the full measure of its days. Uniform experience shows, however, that, provided no accident occur to interrupt the usual course, in proportion as body and mind approximate to this state, life is long; and as they recede from it, it is short. Improvement of the physical condition affords a foundation for the improvement of the mental state; improvement of the mental state improves up to a certain point the physical condition; and in the ratio in which this twofold improvement is effected, the duration of life increases.

Longevity then is a good, in the first place, because it is a sign and a consequence of the possession of a certain amount of enjoyment; and in the second place, because this being the case, of course in proportion as the term of life is extended, the sum of enjoyment must be augmented. And this view of longevity assigns the cause, and shows the reasonableness of that desire for long life which is so universal and constant as to be commonly considered instinctive. Longevity and happiness, if not invariably, are generally, co-incident.

If there may be happiness without longevity, the converse is not possible: there cannot be longevity without happiness. Unless the state of the body be that of tolerable health, and the state of the mind that of tolerable enjoyment, long life is unattainable: these physical and mental conditions no longer existing, nor capable of existing, the desire of life and the power of retaining it cease together.

An advanced term of life and decrepitude are commonly conceived to be synonymous: the extension of life is vulgarly supposed to be the protraction of the period of infirmity and suffering, that period which is characterized by a progressive diminution of the power of sensation, and a consequent and proportionate loss of the power of enjoyment, the "sans teeth, sans eyes, sans taste, sans every thing." But this is so far from being true, that it is not within the compass of human power to protract in any sensible degree the period of old age properly so called, that is, the stage of decrepitude. In this stage of existence, the physical changes that successively take place clog, day by day, the vital machinery, until it can no longer play. In a space of time, fixed within narrow limits, the flame of life must then inevitably expire, for the processes that feed it fail. But though, when fully come, the term of old age cannot be extended, the coming of the term may be postponed. To the preceding stage, an indefinite number of years may be added. And this is a fact of the deepest interest to human nature.

The division of human life into periods or epochs is not an arbitrary distinction, but is founded on constitutional differences in the system, dependent on different physiological conditions. The periods of infancy, childhood, boyhood, adolescence, manhood, and old age, are distinguished from each other by external characters, which are but the outward signs of internal states. In physiological condition, the infant differs from the child, the child from the boy, the boy from the man, and the adult from the old man, as much in physical strength as in mental power. There is an appointed order in which these several states succeed each other; there is a fixed time at which one passes into another. That order cannot be inverted: no considerable anticipation or postponement of that fixed time can be effected. In all places and under all circumstances, at a given time, though not precisely at the same time in all climates and under all modes of life, infancy passes into childhood, childhood into boyhood, boyhood into adolescence, and adolescence into manhood. In the space of two years from its birth, every infant has ceased to be an infant, and has become a child; in the space of six years from this period, every male child will have become a boy; add eight years to this time, and every boy will have become a young man; in eight years more, every young man will have become an adult man; and in the subsequent ten years, every adult man will have acquired his highest state of physical perfection. But at what period will this state of physical perfection decline? What is the maximum time during which it can retain its full vigour? Is that maximum fixed? Is there a certain number of years in which, by an inevitable law, every adult man necessarily becomes an old man? Is precisely the same number of years appointed for this transition to every human being? Can no care add to that number? Can no imprudence take from it? Does the physiological condition or the constitutional age of any two individuals ever advance to precisely the same point in precisely the same number of years? Physically and mentally, are not some persons older at fifty than others are at seventy? And do not instances occasionally occur in which an old man, who reaches even his hundredth year, retains as great a degree of juvenility as the majority of those who attain to eighty?

If this be so, what follows? One of the most interesting consequences that can be presented to the human mind. The duration of the periods of infancy, childhood, boyhood, and adolescence, is fixed by a determinate number of years. Nothing can stay, nothing retard, the succession of each. Alike incapable of any material protraction is the period of old age. It follows that every year by which the term of human existence is extended is really added to the period of mature age; the period when the organs of the body have attained their full growth and put forth their full strength; when the physical organization has acquired its utmost perfection; when the senses, the feelings, the emotions, the passions, the affections, are in the highest degree acute, intense, and varied; when the intellectual faculties, completely unfolded and developed, carry on their operations with the greatest vigour, soundness, and continuity; in a word, when the individual is capable of receiving and of communicating the largest amount of the highest kind of enjoyment.

A consideration more full of encouragement, more animating, there cannot be. The extension of human life, in whatever mode and degree it may be possible to extend it, is the protraction of that portion of it, and only of that portion of it, in which the human being is capable of RECEIVING AND OF COMMUNICATING THE LARGEST MEASURE OF THE NOBLEST KIND OF ENJOYMENT.

Considerations, purely physiological, establish this indubitably; but it is curious that a class of facts, totally different from those of a physiological nature, equally prove it; namely, the results obtained from the observation of the actual numbers that die at different ages, and the knowledge consequently acquired of the progressive decrement of life. Mortality is subject to a law, the operation of which is as regular as that of gravitation. The labours of my valued friend Mr. Finlaison, the actuary of the National Debt, have not only determined what that law is in relation to different nations at different periods of their history, but this celebrated calculator has also invented a striking mode of expressing and representing the fact. He constructed a chart on which 100 perpendicular lines, answering to the respective ages of human life, are laid down and numbered in succession. These are crossed at right angles by 500 horizontal lines; so that, in the manner of musical notation, a point may be laid down either on the horizontal line, or on the space between any two of them: and thus, 1000 points may be laid down on each of the perpendicular lines. The horizontal lines are in like manner numbered from 1 to 1000, ascending from the base. Taking any observation which shows the number of living persons that commence, and in like manner the number that die in each particular year of human life, the calculator reduced by the rule of three every such actual number of living persons for every separate year to 10,000: he next showed the corresponding proportion of deaths out of such 10,000. These proportions he represented on the chart by a point inserted on the horizontal line or space for the number of deaths, and on the perpendicular line for the particular age. He then connected all the points so laid down, and the result is a curve, representing the track of death through an equal number of human beings existing at each age of life. As the curve rises on the perpendicular line, at any given age, it indicates by so much an increase of the mortality at that age; and as the curve falls, the reverse is denoted.

Now, it is a highly interesting fact, that the curves on this chart drawn upon it before the physiological phenomena were known to the operator, placed there because such he found to be the actual path along which death marshals his course, exactly correspond to the epochs which physiology teaches to be determinate stages of human existence. The infant, the child, the boy, the adolescent, the man, the old man, are not exposed to the same danger. The liability of each to death is not merely different; it is widely different; the liability of each class is uniformly the same, the circumstances influencing life remaining the same; and under no known change of circumstances does the relative liability of the class vary; under no change does the liability of the adolescent become that of the infant, or the liability of the adult that of the aged. Take from any statistical document any number of persons; observe out of this number the proportion that dies at the different stages just enumerated; and the period of human life which admits of extension will be strikingly manifest. Take with this view the Prussian statistical tables, the general correctness of which is admitted. From these tables it appears, and the correctness of the result is confirmed by a multitude of other tables, that out of a million living male births, there will die in the first year of life 180,492 infants, and out of the like number of living female births, there will die 154,705 infants. Let us follow up the decrement of life through the different epochs of human existence, confining our observations to the male sex, in which the development is more emphatically marked.

In Mr. Finlaison's report, printed by the House of Commons on the 30th of March, 1829, there are six original observations on the mortality of as many separate sets of annuitants of the male sex.

From an examination and comparison of these observations, it appears—1st. That the rate of mortality falls to a minimum at the close of the period of childhood. 2d. That from this point the mortality rises until the termination of adolescence or the commencement of adult age. 3d. That from the commencement of adult age the mortality again declines, and continues to decline to the period of perfect maturity. And 4th. That from the period of perfect maturity, the mortality rises, and uniformly, without a single exception, returns, at the age of forty-eight, to the point at which it stood at the termination of adolescence. These results clearly indicate that certain fixed periods are marked by nature as epochs of human life; and that at the date of the recorded facts which furnish the data for these observations, and as far as regards the class of persons to which they relate, the age of forty-eight was the exact point at which the meridian of life was just passed, and a new epoch began. The following table exhibits at one view the exact results of each of the observations. For example,

The observation, No. 15, is founded on the large mass of 9,347 lives and 4,870 deaths. From this observation, it appears that, at the age of thirteen, the mortality out of a million is 5,742, being 174,750 less than in the first year of infancy At the age of twenty-three, it is 15,074, being 9,332 more than at the close of childhood. At the age of thirty-four, the period of complete manhood, it falls to 11,707, being 3,367 less than at the close of adolescence. At the age of forty-eight, the mortality returns to 14,870, all but identically the same as at twenty-three, the adult age. From the age of forty-eight, when, as has been stated, life just begins to decline from its meridian, the mortality advances slowly, but in a steady and regular progression. Thus, at the age of fifty-eight it is 29,185, being 14,315 more than at the preceding decade, or almost exactly double. At the age of sixty-eight, it is 61,741, being 32,556 more than at the preceding decade, or more than double. At the age of seventy-eight, it is 114,255, being 52,514 more than at the preceding decade. At the age of eighty-eight, it is 246,803, being 132,548 more than at the preceding decade.

During the first year of infancy, as has been shown, the mortality out of a million is 180,492. At the extreme age of eighty-four, it is 178,130, very nearly the same as in the first year of infancy. Greatly as the mortality of all the other epochs of life is affected by country, by station, by a multitude of influences arising out of these and similar circumstances; yet the concurrent evidence of all observation shows that at this and the like advanced ages the mean term of existence is nearly the same in all countries, at all periods, and among all classes of society. Thus, among the nobility and gentry of England, the expectation of life at eighty-four is four years; among the poor fishermen of Ostend, it is precisely the same. M. De Parcieux, who wrote just ninety years ago, establishes the expectation of life at that time in France, at the same age, to have been three and a half years; and Halley, who wrote 120 years ago, and whose observations are derived from documents which go back to the end of the seventeenth century, states the expectation of life at eighty-four to be two years and nine months.

From these statements, then, it is obvious, that from the termination of infancy at three years of age, a decade of years brings childhood to a close, during which the mortality, steadily decreasing, comes to its minimum. Another decade terminates the period of adolescence, during which the mortality as steadily advances. A third decade changes the young adult into a perfect man, and during this period, the golden decade of human life, the mortality again diminishes; while, during another decade and a half, the mortality slowly rises, and returns at the close of the period to the precise point at which it stood at adult age. Thus the interval between the period of birth and that of adult age includes a term of twenty-three years. The interval between the period of adult age and that when life just begins to decline from its meridian, includes a term of twenty-four years: consequently, a period more than equal to all the other epochs of life from birth to adult age is enjoyed, during which mortality makes no advance whatever. Now the term of years included in the several epochs that intervene between birth and adult age is rigidly fixed. Thus the period of infancy includes precisely three years, that of childhood ten years, and that of adolescence ten years. Within the space of time comprehended in these intervals, physiological changes take place, on which depend every thing that is peculiar to the epochs. These changes cannot be anticipated, cannot be retarded, except in a very slight degree. In all countries, among all classes, they take place in the same order and nearly in the same space of time. In like manner, in extreme old age, or the age of decrepitude, which may be safely assumed to commence at the period when the mortality equals that of the first year of infancy, namely, the age of eighty-four, physiological changes take place, which, within a given space of time, inevitably bring life to a close. That space of time, in all countries, in all ranks, in all ages, or rather as far back as any records enable us to trace the facts, appears to be the same. As within a given time the boy must ripen into manhood, so within a given time the man of extreme old age must be the victim of death. Consequently, it is the interval between the adult age and the age of decrepitude, and only this, that is capable of extension. During the interval between adult age and the perfect meridian of life, comprehending at present, as we have seen, a period of twenty-four years, the constitution remains stationary, mortality making no sensible inroad upon it. But there is no known reason why this stationary or mature period of life should, like the determinate epochs, be limited to a fixed term of years. On the contrary, we do in fact know that it is not fixed; for we know that the physiological changes on which age depends are, in some cases, greatly anticipated, and in others, proportionately postponed; so that some persons are younger at sixty, and even at seventy, than others are at fifty; whereas, an analogous anticipation or postponement of the other epochs of life is never witnessed. So complete is the proof, that the extension of human life can consist in the protraction neither of the period of juvenility, nor in that of senility, but only in that of maturity.

Were it necessary to adduce further evidence of this most interesting fact, it would be found equally in the statistics of disease as in those of mortality. Indeed, the evidence derived from both these sources must be analogous, because mortality is invariably proportionate to the causes of mortality, of which causes, sickness, in all its forms, may be taken as the general or collective expression.

We do not possess the same means of illustrating the prevalence of disease through all the epochs of life as we do of showing the intensity of mortality; yet the report of Mr. Finlaison, already referred to, enables us to show its comparative prevalence at several of those stages. Thus, from this document, it appears, that among the industrious poor of London, members of benefit societies, out of a million of males, the proportion constantly sick at the age of twenty-three, is 19,410; at the age of twenty-eight, it is 19,670; at the age of thirty-three, it is 19,400; at the age of thirty-eight, it is 23,870; at the age of forty-three, it is 26,260; at the age of forty-eight, it is 26,140; at the age of fifty-three, it is 27,060; at the age of fifty-eight, it is 36,980; at the age of sixty-three, it is 57,000; at the age of sixty-eight, it is 108,040; at the age of seventy-three and upwards, it is 317,230. The prevalence of sickness is not an exact and invariable measure of the intensity of mortality; but there is a close connexion between them, as is manifest from the progressively increasing amount of sickness, as age advances. Thus, in the first ten years from the age of twenty-three to that of thirty-three, there is no increase of sickness, its prevalence is all but identically the same; in the next ten years from the age of thirty-three to that of forty-three, the increase of sickness, as compared with that of the preceding decade, is 6,860; in the next ten years from the age of forty-three to that of fifty-three, the increase is only 800; in the next ten years from the age of fifty-three to that of sixty-three, the increase is 29,940, while from the age of sixty-three to seventy-three, it is 260,230.

Such are the results derived from the experience of disease considered in the aggregate, all its varied forms taken together. I am enabled further to present an exact and most instructive proof, that one particular disease which, in this point of view, may be considered as more important than any other, because it is the grand agent of death, namely fever, carries on its ravages in a ratio which steadily and uniformly increases as the age of its victim advances. Having submitted the experience of the London Fever Hospital for the ten years preceding January 1834, an observation including nearly 6,000 patients affected with this malady, to Mr. Finlaison, it was subjected by him to calculation. Among other curious and instructive results to be stated hereafter, it was found that the mortality of fever resolves itself into the following remarkable progression. Thus suppose 100,000 patients to be attacked with this disease between the ages of 5 and 16, of these there would die - 8,266 and of an equal number

Thus the risk of life from this malady is twice as great at the age of thirty-one as it is at eleven. It is also nearly twice as great at forty-one as it is at twenty-one. It is five times as great at sixty-one as it is at eleven, and nearly four times as great above sixty-five as it is at twenty-one.

From the whole of the foregoing statements, it is manifest that life is a fluctuating quantity. In order to compare this fluctuating quantity under different circumstances, writers on this branch of statistics use several terms, the exact meaning of which it is desirable to explain. It is, for example, very important to have a clear understanding of what is meant by such expressions as the following: the expectation, the probability, the value, the decrement of life, and the law of mortality.

1. The Expectation of Life. It is important to bear in mind that several expressions in common use have a signification perfectly synonymous with this: namely, share of existence; mean duration of life; la vie moyenne.

By these terms is expressed the total number of years, including also the fractional parts of a year, ordinarily attained by human beings from and after any given age. Suppose, for example, that one thousand persons enter on the eighty-sixth year of their age: suppose the number of years and days which each one of them lives afterwards be observed and recorded; suppose the number ultimately attained by each be formed into a sum total; suppose this total be divided equally among the thousand, the quotient of this division is said to be each one's share of existence, or his mean duration of life, or his expectation of life. Thus, of the thousand persons in the present case supposed to commence the age of eighty-five, suppose the number of years they collectively attain amount to 3,500 years: the one-thousandth part of 3,500 is three and a half: three years and a half then is said to be the expectation of life at the age of eighty-five, because, of all the persons originally starting, this is the equal share of existence that falls to the lot of each.

2. Probability of Life; or the probable duration of life, la vie probable. These are synonymous terms, in use chiefly among continental writers as an expression of the comparative duration of life. The tabular methods of setting forth the duration of life consist, for the most part, in assuming that 10,000 infants are born; and that at the age of one, two, three, and each successive year of life, there are so many still remaining in existence. Fix on any age; observe what number remain alive to commence that age; note at what age this number decreases to one-half; the age at which they so come to one-half is called the probable term of life; because, say the continental writers, it is an equal wager whether a person shall or shall not be alive at that period. Thus, suppose one thousand males commence together the age of eighty-four; suppose the table indicate that there will be alive at the age of eighty-five, 817; at the age of eighty-six, 648; at the age of eighty-seven, 493; at the age of eighty-eight, 357, and so on. In the present case, the probable duration of life at eighty-four is said to be very nearly three years, because, at the age of eighty-seven there are left alive 493, very nearly one-half of the thousand that originally started together.

3. Value of Life. This term, when used accurately, expresses the duration of life as measured by one or other of the methods already expounded. But it is sometimes popularly used in a loose and singularly inaccurate sense. Thus it is very commonly said—"Such a man's life is not worth ten years' purchase," which is the same thing as to say, that an annuity, suppose a hundred pounds a year, payable during the life of the person in question, is not worth ten times its magnitude, that is one thousand pounds. If a thousand pounds be put into a bank at some rate of interest to be agreed upon, and if a hundred pounds be drawn every year from the stock, the expression under consideration affirms that the person in question will be dead before the principal and interest are exhausted. For instance, at four per cent., the value of an annuity of one hundred pounds to a man of the age of twenty-five is 1694l., which is 16-9/10 years' purchase; whereas, his expectation of life at that age is 35-9/10 years.

4. Law of Mortality. By this term is expressed the proportion out of any determinate number of human beings who enter on a given year of age, that will die in that year. Every observation on the duration of life presents certain numbers, which, by recorded facts, are found to pass through each year of age, and also shows how many have died or failed to pass through every year of age. Those numbers, by the rule of three, are converted into the proportions who would die at each age out of one million of persons, if such a number had commenced it. Suppose, then, a million of persons to be in existence at the first year of age; suppose a million to be in existence at the second year of age; suppose a million to be in existence at the third year of age; and in this manner suppose an equal number to be in existence at the commencement of each and every year to the extreme term of human life. Now, the proportions that by actual observation are found to die at each and every year out of the million that were alive at the commencement of it, form separately the law of mortality for each year, and collectively for the whole of life.

5. Decrement of Life. Assuming, as before, that a million of male children are born alive (for the still-born must be excluded from the calculation) if it be found that 180,492 would die in the first year, it follows that the difference, namely, 819,508, will enter upon the age of one year. Suppose the law of mortality indicate that the proportion that will die, out of a million, between the age of one and two, is 30,000; it is plain that the number who would die out of 819,508 will by the rule of three be 27,863, and consequently that the residue, namely, 791,615, will remain alive, and so enter on the age of two years. This method being pursued through each and every age to the extreme term of life, when none of the original million survive, the result is a table of mortality in the form in which it is commonly presented in the works of writers on this branch of science. In the table thus constructed there is a column containing the number of living persons who, out of the original million, lived to enter upon each and every year. Of this rank of numbers the difference between each term and its next succeeding one, is the number who die in that particular interval: that number is the measure of what is technically called the decrement of life for that particular year, and the whole of the decrements for each and every year taken collectively is termed the decrement of life. The decrement of life, then, is not only not the same as the law of mortality, but is carefully to be distinguished from it. The law of mortality is derived from observing the number who die out of one and the same number which is always supposed to enter on each and every year. The decrement of life constitutes a rank of numbers arising out of the successive deaths; that is, out of the original million in the first year; out of the survivors of that million in the second year; out of the survivors of those survivors in the third year, and so on. In the first case the number of the living is always the same; the number that die is the variable quantity: in the second case the number of the living is the variable quantity, while the number that die may remain pretty much the same for a succession of years; and on casting the eye on the tables constructed in the ordinary mode, it will be seen that the number often does remain the same for a considerable series of years.

We have said that life is a fluctuating quantity. It fluctuates in different countries at the same period; in the same country at different periods; in the same country, at the same period, in different places; in the same country, at the same period, in the same place, among different classes; in the same country, at the same period, in the same place, among the same class, at the different determinate stages of life. Some few of these fluctuations, and more especially the last, depend on the primary constitution of the organization in which life itself has its seat, over which man has little or no control. The greater part of them depend on external and adventitious agencies over which man has complete control. Human ignorance, apathy, and indolence, may render the duration of life, in regard to large classes and entire countries, short; human knowledge, energy and perseverance, may extend the duration of life far beyond what is commonly imagined. It will be interesting and instructive to select a few of the more striking examples of this from the records we possess, few and imperfect as they are, in relation to this subject.

Of the duration of life in the earlier periods of the history of the human race we know nothing with exactness, though there are incidental statements which afford the means of deducing with some probability the rate of mortality in particular situations. There has come down to us one document through Domitius Ulpianus, a judge, who flourished in the reign of Alexander Severus, which enables us to form a probable conjecture at least of the opinion of the Roman people of the value of life among the citizens of Rome in that age. It happened at Rome as in other countries, that when an estate came into the possession of an individual it was burthened with a provision for another person during the life of the latter, a younger brother, for example. This provision was called by the Romans an aliment. No estate, burthened with such a provision, could be sold by the heir in possession, unless the purchaser retained in his hands so much of the price as was deemed adequate to secure the regular and continuous payment of the aliment. This imposed upon the Romans the necessity of considering what the term of life would probably be from and after any given age. What they did conceive that term to be is stated in a document of Ulpianus, recorded by Justinian, and given in the note below.[1] This document imports that from infancy up to the age of

But between 40 and 50, as many years were to be allowed as the age of the party fell short of 60, deducting one year.

No clue has hitherto been obtained to the discovery of the real meaning of this document. It is, however, highly probable that the Romans had fallen on one of the two methods of measuring the value of life already explained; namely, that termed the Probability of Life. Of the two modes of determining the value of life, the probability was more likely to occur to a Roman judge than the expectation. He had no tables, no registers to guide him. What course, then, would he be likely to take? Probably he would form a list of his own school-fellows and others within his own knowledge, of the age, say, of twenty. By prevailing on persons of his own age, on whose correctness he could rely, to draw out similar lists, he might accumulate some thousand names. In this list it is probable that the male sex alone would be included, on account of the greater ease of ascertaining both their exact age and the exact date of their death. For the same reason, it is probable that the list would consist only of the nobility and the inhabitants of towns. Having thus completed his list, the next step would be to frame another list of all who died at the age of twenty-one; and next, another list of all who died at the age of twenty-two, and so on through each and every year of life. Now by subtracting the number in the list, No. 1, that is, those who died between twenty and twenty-one, from the number who originally started at twenty, which, in other words, would be to find the decrement of life, in the mode already explained, he would see how many lived to commence the age of twenty-one, and so on, through each year of life. But this would be to construct a table, showing the probable duration of life; that is, a table from which he could observe at what advanced age the number originally starting at twenty, and so on, came to diminish to one-half, when it would naturally occur to him that it is an equal wager whether such younger life would or would not be in existence at the advanced age so ascertained. If we suppose this to have been the method actually adopted by the Roman judge, and apply it to the table of Ulpianus, the result obtained is consistent in an extraordinary degree, and is highly interesting.

There is reason to believe that the mortality at present throughout Europe, taking all countries together, including towns and villages, and combining all classes into one aggregate, is one in thirty-six. Süssmilch, a celebrated German writer, who flourished about the middle of the last century, estimated it at this average at that period. The result of all Mr. Finlaison's investigations is a conviction that the average for the whole of Europe does not materially differ at the present time. He has ascertained by an actual observation, that in the year 1832 it was precisely this in the town of Ostend. Taking this town, then, as the subject of comparison, it is found that the probable duration of life among the male sex at Ostend exceeds the Roman allowance by the following number of years; namely,

At the age of 17, the excess in round

But it is not improbable that the Romans made some deduction from what they knew to be the real value of life among the citizens of Rome, on account of the use of the money appropriated to the aliment, which the purchaser of the estate retained in his own hands. It has been shown that the average mortality at present at Ostend is one in thirty-six; which is the same thing as to assert that a new-born child at Ostend has an expectation of thirty-five and a half years of life. The Roman allowance from birth, à primâ ætate, was thirty years. If we suppose the Romans deducted from the real value of life five and a half years for the interest of money, it would bring the Roman allowance and the duration of life at Ostend to the same. The like deduction at the age of seventeen would likewise bring the probability of life in both cases to the same. It is not likely that the Romans, without any record of the individual facts, and acting only on a general principle of utility, the best they could find, would make any variation for the intermediate years of childhood and youth: consequently the presumption is, that the duration of life at Rome, 1300 years ago, was very much the same as it is throughout Europe at the present day. This estimate, however, for the reasons already assigned, includes only the resident citizens of Rome, the male sex, and the higher classes. What the mortality was at Rome among the lower class, including the slaves—what it was in the Roman provinces, and in the less civilized countries of that age—we have no means of forming even a conjecture. What it was in Europe during the succeeding ages of barbarism we do not know. In civilized Rome, the value of life had probably reached a very high point; in barbarian Europe we may be sure it fell to an exceedingly low point. From that low point, in civilized Europe, it has been slowly but gradually rising, until, in modern times, the whole mass of the European population has, to say the very least, reached the highest point attained by the select class in ancient Rome. But in some favoured spots in Europe, the whole mass has advanced considerably beyond the select class in ancient Rome. In England, for example, the expectation of life, at the present day, for the mass of the people, as compared with that of the mass at Ostend, which, as has been shown, is the same as that of the whole of Europe, is as follows:—

It should be borne in mind that the females of the mass exceed in duration the lives of the males at every age by two or three years.

The earliest statistical document bearing on the rate of mortality, in any European nation, emerging from the state of barbarism, appears to be a manuscript of the fourteenth century, relating to the mortality of Paris, from which M. Villermé has calculated that the mortality of Paris at that period was one in sixteen. How the individual facts contained in this manuscript were collected, from which M. Villermé's calculation is made, does not appear; and it makes the mortality so excessive as to be altogether incredible. Yet a statement scarcely less extraordinary is made with regard to Stockholm, in the middle of the last century. From a table given by Dr. Price, vol. ii., p. 411, it appears that, for all Sweden, between the years 1756 and 1763, the expectation of life

Of males at birth, was Females,
33¼ years.35¾ years.

while at the same time it was at Stockholm,

For males at birth,Females,
14¼ years.18 years.

Whereas, for the twenty years preceding 1800, it
was, for all Sweden, at birth,

MalesFemales,
34¾37½ years.

Hitherto, in all places which man has made his abode, noxious agents have been present which act injuriously upon his body, tending to disturb the actions of its economy, and ultimately to extinguish life. All these noxious agents, of whatever name or quality, may be included under the term Causes of Mortality. Inherent in the constitution of the body are conservative powers, the tendency of which is to resist the influence of these causes of mortality. The actual mortality at all times will of course be according to the relative strength of these destructive agents, and the relative weakness of these conservative powers. There are states of the system tending to enfeeble these conservative powers. Such states become tests, often exceedingly delicate, of the presence and power of the destructive agents to which the body is exposed; and such, more especially, are, the states of parturition, infancy, and sickness. During the prevalence of these states, in which the conservative powers of the body are weak, life is destroyed by causes which do not prove mortal in other conditions of the system. Accordingly, in every age and country, the rate of mortality among its lying-in women, its infants and its sick, may be taken as a measure of the degree in which the state of the whole population is favourable or unfavourable to life.

The change that has taken place in the condition of lying-in women during the last century in all the nations of Europe cannot be contemplated without astonishment. The mortality of lying-in women in France, at the Hôtel Dieu of Paris, in 1780, is stated to have been one in 15. In 1817, for the whole kingdom of Prussia, including all ranks, it was one in 112. In England, in the year 1750, at the British Lying-in Hospital of London, it was one in 42; in 1780, it diminished to one in 60; in the years between 1789 and 1798, it further decreased to one in 288; in 1822, at the Lying-in Hospital of Dublin, it was no more than one in 223; while during the last fifteen years at Lewes, a healthy provincial town, out of 2410 cases there have been only two deaths, that is, one in 1205. There is no reason to suppose that the mortality in the state of parturition is less at Lewes than in any other equally healthy country-town in England.

Equally striking is the proof of the diminished violence of the prevalent causes of disease and death derived from the diminished mortality of children, the vital power of resistance being always comparatively weak in the human infant, and consequently, the agents that prove destructive to life exerting their main force on the new born, and on those of tender age. From mortuary tables, preserved with considerable accuracy at Geneva since the year 1566, it appears that at the time of the Reformation one-half of the children born died within the sixth year; in the seventeenth century, not till within the twelfth year; in the eighteenth century, not until the twenty-seventh year; consequently, in the space of about three centuries, the probability that a child born in Geneva would arrive at maturity has increased fivefold. In the present day, at Ostend, only half of the new-born children attain the age of thirty; whereas, in England, they attain the age of forty-five.

No less remarkable is the progressive diminution of mortality among the sick of all ages. Hippocrates has left a statement, which has come down to our times, of the history and fate of forty-two cases of acute disease. Out of this number, thirty-seven were cases of continued fever; of these thirty-seven febrile cases twenty-one died, above half of the whole. The remaining five were cases of local inflammation, and of these four were fatal; thus, of the whole number of the sick (forty-two), twenty-five were lost. Now, even in the Fever Hospital of London, to which, for the most part, only the worst cases that occur in the metropolis are sent, and even of these many not until so late a period of the disease that all hope of recovery is extinct, the mortality ranges in different years from one in six to one in twelve; and for a period of ten consecutive years, it is no more than one in seven; while, in the Dublin Fever Hospital, where most of the cases are sent very early, the average mortality from 1804 to 1812 was one in twelve. At the Imperial Hospital at Petersburg, the average mortality for fourteen years, ending in 1817, was one in four and a half. In the Charité of Berlin, on an average of twenty years, from 1796 to 1817, it was one in six. At Dresden, it was one in seven; at Munich, it was one in nine, the lowest of any hospital of equal size in Germany. In the year 1685, the average mortality at St. Bartholomew's and St. Thomas's Hospitals was from one in seven to one in ten. During the ten years from 1773 to 1783, it decreased to one in fourteen. From 1803 to 1813, it was one in sixteen. The average for fifty years from 1764 to 1813, was one in fifteen. In the smaller towns, the mortality is still less. It is less in Edinburgh and Dublin than in London; while in the hospital at Bath during 1827, even among the physician's patients, the mortality was only one in twenty. In the German provincial towns, the diminution is still more remarkable. In the hospital at Gottingen, for example, it is only one in twenty-one.

If the accuracy of these statements could be relied on, they would not only afford striking illustrations of the well-known fact that extraordinary differences prevail in the rate of mortality in different places, at different periods, and under different circumstances; but they would further prove that, during the last century, a steady and progressive diminution of mortality has taken place in all the countries of Europe. But of the truth of this there is much more certain evidence than can be derived from calculations, the trustworthiness of the data of which is not established, and the correctness of the calculators not known. Both the fluctuations of mortality and the increase in the value of life in the different countries of Europe, from the earliest period when statistical facts began to be collected and compared, are exhibited in a striking point of view in the following table, drawn up by Mr. Finlaison. The facts relating to selected lives and to the mass of the people are distinguished from each other, in order that they may be contrasted. The data are derived from the most authentic sources, and the calculations are made by men of the highest authority.

Let us trace from this table the differences that have taken place, in different countries at different periods, in the duration of life at a given age. Let us take the age given in the first column, namely, fifty. Assuming, then, the highest degree of longevity hitherto attained at the age of fifty to be twenty-three years, it appears that, between the years 1700 and 1725, the mass of the people in Breslau, in Silesia, fell short of reaching this period by 275 weeks; the inhabitants of the town of Ostend in Flanders, between 1805 and 1832, by 276 weeks; the nominees of the tontine of England, between the years 1693 and 1775, by 269 weeks; the inhabitants of the town of Northampton in England, between 1735 and 1780, by 209 weeks; the mass of the people in Sweden, between 1775 and 1795, by 207 weeks; the public annuitants of Holland, between 1615 and 1740, by 186 weeks; the inhabitants of all Belgium, between 1725 and 1832, by 183 weeks; the persons assured at the Equitable Office, between 1760 and 1834, by 119 weeks; the inhabitants of all England and Wales, between 1811 and 1831, by 100 weeks; the English government annuitants, between 1775 and 1832, only by 35 weeks.

From these statements, it appears that, towards the close of the seventeenth century, the duration of life in England was considerably less than in France: less even than in Holland nearly a century earlier. Thus, the nominees of the tontine of France, between the years 1693 and 1745, at the age of fifty, according to M. De Parcieux, fell short of the maximum longevity by 133 weeks; the public annuitants of Holland, seventy-eight years before, namely, between the years 1615 and 1740, according to M. Kersseboom, fell short of the maximum longevity by 186 weeks; whereas, the nominees of the tontine of England, between the years 1693 and 1775, according to Mr. Finlaison, fell short of it by 269 weeks; a difference nearly double that of Holland, and quite double that of France in persons of the corresponding rank in society.

Since that period, surprising changes have taken place in all the nations of Europe; but in none has the change been so great as in England. From that period, when its mortality exceeded that of any great and prosperous European country, its mortality has been steadily diminishing, and at the present time the value of life is greater in England than in any other country in the world. Not only has the value of life been regularly increasing until it has advanced beyond that of any country of which there is any record; but the remarkable fact is established, that the whole mass of its people now live considerably longer than its higher classes did in the seventeenth and eighteenth centuries. Thus, by inspecting the preceding table, it will be seen that between the years 1693 and 1715, the nominees of the tontine of England, at the age of fifty, fell short of the maximum longevity by 269 weeks; whereas, the mass of the people in all England and Wales, between the years 1811 and 1831, fell short of it only by 100 weeks; the entire mass having not only reached the select class, but absolutely advanced beyond it by 169 weeks.

There cannot be a more interesting and instructive thing than to connect these facts with their causes. This will be attempted in a subsequent part of this work; but the reader will be incomparably better prepared for the investigation when the processes of life have been explained, and the influence of physical and moral agents upon them traced. And with this exposition we now proceed.

CHAPTER V.

Ultimate elements of which the body is composed—Proximate principles—Fluids and solids—Primary tissues—Combinations—Results—Organs, systems, apparatus—Form of the body—Division into head, trunk, and extremities—Structure and function of each—Regions—Seats of the more important internal organs.

1. The ultimate elements of which the human body is composed are azote, oxygen, and hydrogen (gaseous fluids); and carbon, phosphorus, calcium, sulphur, sodium, potassium, magnesium, and iron (solid substances). These bodies are called elementary and ultimate, because they are capable of being resolved by no known process into more simple substances.

2. These elementary bodies unite with each other in different proportions, and thus form compound substances. A certain proportion of azote uniting with a certain proportion of oxygen, hydrogen, and carbon, forms a compound substance possessing certain properties. Another proportion of azote uniting with a different proportion of oxygen, hydrogen, and carbon, forms another compound substance possessing properties different from the former. Oxygen, hydrogen, and carbon, uniting in still different proportions without any admixture of azote, form a third compound possessing properties different from either of the preceding. The compounds thus formed by the primary combinations of the elementary substances with each other are called PROXIMATE PRINCIPLES.

3. Each proximate principle constitutes a distinct form of animal matter, of which the most important are named gelatin, albumen, fibrin, oily or fatty matter, mucus, urea, pichromel, osmazome, resin, and sugar.

4. By chemical analysis it is ascertained that all the proximate principles of the body, however they may differ from each other in appearance and in properties, are composed of the same ultimate elements. Gelatin, for example, consists (in 100 parts) of azote 16-988/1000, oxygen 27-207/1000, hydrogen 7-914/1000, carbon 47-881/1000 parts. The elementary bodies uniting in the above proportions form an animal substance, soft, tremulous, solid, soluble in water, especially when heated, and on cooling, which may be considered as its distinctive property, separating from its solution in water into the same solid substance, without undergoing any change in its chemical constitution.

5. Again, albumen consists of azote 15-705/1000, oxygen 23-872/1000, hydrogen 7-540/1000, carbon 52-888/1000, parts. The elementary bodies uniting in these different proportions, there results a second proximate principle, an adhesive fluid, transparent, destitute of smell and taste, miscible in water, but when subjected to a temperature of about 165°, converted into a solid substance no longer capable of being dissolved in water. This conversion of albumen from a fluid, which is its natural state, into a solid, by the application of heat, is called coagulation. It is a process familiar to every one. The white of egg is nearly pure albumen, naturally a glary and adhesive fluid: by boiling, it is coagulated into a white and firm solid.

6. In like manner, fibrin consists of azote 19-934/1000, oxygen 19-685/1000, hydrogen 7-021/1000, carbon 53-360/1000 parts, forming a solid substance of a pale whitish colour and firm consistence, the peculiar character of which is its disposition to arrange itself into minute threads or fibres.

7. On the other hand, fat or oil, which is a fluid substance of a whitish yellow colour, inodorous, nearly insipid, unctuous, insoluble in water and burning with rapidity, consists of a larger proportion of hydrogen, a small proportion of oxygen, and a still smaller proportion of carbon, without any admixture of azote.

8. From this account of the composition of the proximate principles, which it is not necessary to extend further, it is manifest that all of them consist of the same ultimate elements, and that they derive their different properties from the different proportions in which their elements are combined.

9. The ultimate elements that compose the body are never found in a separate or gaseous state, but always in combination in the form of one or other of the proximate principles.

10. In like manner, the proximate principles never exist in a distinct and pure state, but each is combined with one or more of the others. No part consists wholly of pure albumen, gelatin, or mucus, but albumen is mixed with gelatin, or both with mucus.

11. Simple or combined, every proximate principle assumes the form either of a fluid or of a solid, and hence the most general and obvious division of the body is into fluids and solids. But the terms fluid and solid are relative, not positive; they merely express the fact that some of the substances in the body are soft and liquid compared with others which are fixed and hard; for there is no fluid, however thin, which does not hold in solution some solid matter, and no solid, however dense, which does not contain some fluid.

12. Fluids and solids are essentially the same in nature; they differ merely in their mode of aggregation; hence the easy and rapid transition from the one to the other which incessantly takes place in the living body, in which no fluid long remains a fluid, and no solid a solid, but the fluid is constantly passing into the solid and the solid into the fluid.

13. The relative proportion of the fluids in the human body is always much greater than that of the solids; hence its soft consistence and rounded form. The excess, according to the lowest estimate, is as 6 to 1, and according to the highest, as 10 to 1. But the proportion is never constant; it varies according to age and to the state of the health. The younger the age, the greater the preponderance of the fluids. The human embryo, when first perceptible, is almost wholly fluid: solid substances are gradually but slowly superadded, and even after birth the preponderance is strictly according to age; for in the infant, the fluids abound more than in the child; in the child, more than in the youth; in the youth, more than in the adolescent; in the adolescent, more than in the adult; and in the adult, more than in the aged. Thus, among the changes that take place in the physical constitution of the body in the progress of life, one of the most remarkable is the successive increase in the proportion of its solid matter: hence the softness and roundness of the body in youth; its hard, unequal, and angular surface in advanced life; its progressively increasing fixedness and immobility in old age, and ultimate inevitable death.

14. The fluids are not only more abundant than the solids, but they are also more important, as they afford the immediate material of the organization of the body; the media by which both its composition and its decomposition are effected. They bear nourishment to every part, and by them are carried out of the system its noxious and useless matter. In the brain they lay down the soft and delicate cerebral substance; in the bone, the hard and compact osseous matter; and the worn-out particles of both are removed by their instrumentality. Every part of the body is a laboratory in which complicated and transforming changes go on every instant; the fluids are the materials on which these changes are wrought; chemistry is the agent by which they are effected, and life is the governing power under whose control they take place.

15. The fluids, composed principally of water holding solid matter in solution, or in a state of mechanical division, either contribute to the formation of the blood, or constitute the blood, or are derived from the blood; and after having served some special office in a particular part of the system, are returned to the blood; and according to the nature and proportion of the substances they contain, are either aqueous, albuminous, mucous, gelatinous, fibrinous, oleaginous, resinous, or saline.

16. When the analysis of the different kinds of animal matter that enter into the composition of the body has been carried to its ultimate point, it appears to be resolvable into two primitive forms: first, a substance capable of coagulation, but possessing no determinate figure; and secondly, a substance having a determinate figure and consisting of rounded particles. The coagulable substance is capable of existing by itself; the rounded particles are never found alone, but are invariably combined with coagulated or coagulable matter. Alone or combined with the rounded particles, the coagulable matter forms, when liquid, the fluids, when coagulated, the solids.

17. When solid, the coagulable substance is disposed in one of two forms, either in that of minute threads or fibres, or in that of minute plates or laminæ; hence every solid of the body is said to be either fibrous or laminated. The fibres or laminæ are variously interwoven and interlaced, so as to form a net-work or mesh; and the interspaces between the fibres or laminæ are commonly denominated areolæ or cells (fig. XVII).

18. This concrete substance, fibrous or laminated, is variously modified either alone or in combination with the rounded particles. These different modifications and combinations constitute different kinds of organic substance. When so distinct as obviously to possess a peculiar structure and peculiar properties, each of these modifications is considered as a separate form of organized matter, and is called a PRIMARY TISSUE. Anatomists and physiologists have been at great pains to discriminate and classify these primary tissues; for it is found that when employed in the composition of the body, each preserves its peculiar structure and properties wherever placed, however combined, and to whatever purpose applied, undergoing only such modification as its local connexions and specific uses render indispensable. Considering every substance employed in the construction of the body, not very obviously alike, as a distinct form of organized matter, these primary tissues may be said to consist of five, namely, the membranous, the cartilaginous, the osseous, the muscular, and the nervous.

19. The first primary tissue is the peculiar substance termed MEMBRANE. It has been already stated (16) that one of the ultimate forms of animal matter is a coagulable substance, becoming concrete or solid under the process of coagulation. The commencement of organization seems to be the arrangement of this concrete matter into straight thready lines, at first so small as to be imperceptible to the naked eye. Vast numbers of these threads successively uniting, at length form a single thread of sufficient magnitude to be visible, but still smaller than the finest thread of the silkworm. If the length of these threads be greater than their breadth, they are called fibres; if, on the contrary, their breadth exceed their length, they are termed plates or laminæ. By the approximation of these fibres or plates in every possible direction, and by their accumulation, combination, and condensation, is constituted the simplest form of organized substance, the primary tissue called membrane.

20. Membrane once formed is extensively employed in the composition of the body: it is indeed the material principally used in producing, covering, containing, protecting, and fixing every other component part of it. It forms the main bulk of the cartilaginous tissue; it receives into its cells the earthy matter on which depend the strength and hardness of the osseous tissue; it composes the canals or sheaths in which are deposited the delicate substance of the muscular, and the still more tender pulp of the nervous tissue; it gives an external covering to the entire body; it lines all its internal surfaces; it envelopes all internal organs; it enters largely as a component element into the substance of every organ of every kind; it almost wholly constitutes all the internal pouches and sacs, such as the stomach, the intestines, the bladder; and all tubes and vessels, such as arteries, veins, and lymphatics; it furnishes the common substance in which all the parts of the body are, as it were, packed; it fills up the interstices between them; it fixes them in their several situations; it connects them all together; in a word, it forms the basis upon which the other parts are superinduced; or rather the mould into which their particles are deposited; so that were it possible to remove every other kind of matter, and to leave this primary tissue unaltered in figure and undiminished in bulk, the general form and outline of the body, as well as the form and outline of all its individual parts, would remain unchanged.

21. The properties which belong to membrane are cohesion, flexibility, extensibility, and elasticity. By its property of cohesion, the several parts of the body are held together; by its combined properties of cohesion, flexibility, and extensibility, the body in general is rendered strong, light, and yielding, while particular parts of it are made capable of free motion. But elasticity, that property by which parts removed from their situation in the necessary actions of life are restored to their natural position, may be regarded as its specific property. The varied purposes accomplished in the economy by the property of elasticity will be apparent as we advance in our subject. Meantime, it will suffice to observe that it is indispensable to the action of the artery in the function of the circulation; to the action of the thorax in the function of respiration; to the action of the joints in the function of locomotion: in a word, to the working of the entire mechanism by which motion of every kind and degree is effected. All these properties are physical, not vital; vital properties do belong even to this primary form of animal matter; but they are comparatively obscure. In the tissue with which organization commences, and which is the least removed from an inorganic substance, the properties that are prominent and essential are merely physical.

22. By chemical analysis, membrane is found to contain but a small proportion of azote, the peculiar element of animal matter. Its proximate principles are gelatin, albumen, and mucus. In infancy and youth, gelatin is the most abundant ingredient; at a more advanced period, albumen predominates[3]. Gelatin differs from albumen in containing a less proportion of azote and a greater proportion of oxygen; on both accounts it must be regarded as less animalized. Thus animalization bears a certain relation to organization. The simplest animal tissue is the least animalized, and the least of all at the earliest period of life. Not only are the physical and mental powers less developed in the young than in the adult, but the very chemical composition of the primary tissue of which the body is constructed is less characteristic of the perfect animal.

23. Membrane exists under several distinct forms; a knowledge of the peculiarities of which will materially assist us in understanding the composition of the body. The simplest form of membrane, and that which is conceived to constitute the original structure from which all the others art produced, is termed the cellular. When in thin slices, cellular membrane appears as a semi-transparent and colourless substance; when examined in thicker masses, it is of a whitish or greyish colour. It consists of minute threads, which cross each other in every possible direction, leaving spaces between them, and thus forming a mesh or net-work (fig. XVII.), not unlike the spider's web. The term cells, given to these interspaces, is employed rather in a figurative sense than as the expression of the fact; for there are no such distinct partitions as the term cell implies. The best conception that can be formed of the arrangement of the component parts of this structure is, to suppose a substance consisting of an infinite number of slender thready lines crossing each other in every possible direction (fig. XVII.). The interspaces between these lines during life, and in the state of health, are filled with a thin exhalation of an aqueous nature, a vapour rather than a fluid, rendering and keeping the tissue always moist. This vapour consists of the thinner part of the blood, poured into these interstitial spaces by a process hereafter to be described, termed secretion. When occupying those spaces, it makes no long abode within them, but is speedily removed by the process of absorption. In health, these two operations exactly equal each other; but if any cause arise to disturb the equilibrium, the vapour accumulates, condenses and forms an aqueous fluid, which distends the cells and gravitates to the most depending parts. Slightly organized as this tissue is, and indistinct as its vita functions may be, it is obvious that it must be the seat of at least two vital functions, secretion and absorption.

A single film of the cellular tissue lifted up and
slightly distended.

24. It is certain that the interspaces or cells of this membrane have no determinate form or size, that they communicate freely with each other, and that this communication extends over the whole body; for if a limb which has been infiltrated be frozen, a thousand small icicles will be formed, assuming the shape of the containing cells, some of which are found to be circular and others cylindrical, and so on. If air or water escape into any particular part of the body, it is often effused over the whole extent of it, and butchers are observed to inflate animals by making a puncture in some part where the cellular tissue is loose, and from this one aperture the air is forced to the most distant parts of the body.

25. Cellular membrane, variously modified and disposed, forms the main bulk of all the other solid parts of the body, constituting their common envelope and bond of union, and filling up all their interstices. It is dense or loose, coarse or fine, according to its situation and office. Wherever it is subject to pressure, it is dense and firm, as in the palm of the hand and the sole of the foot; around the internal organs it is more loose and delicate, and it becomes finer and finer as it divides and subdivides, in order to envelope the soft and tender structures of the body.

A portion of cellular tissue, very highly magnified, showing
the strings of globules of which its ultimate fibres are by
some supposed to consist.

26. According to some who have carefully examined with the microscope its component threads, they consist of minute particles of a globular figure (fig. XVIII.); other microscopical observers regard the cellular threads as coagulated or condensed animal substance, perfectly amorphous (without form).

27. Every part of this tissue is penetrated by arteries, veins, absorbents, and nerves, endowing it with properties truly vital, though in a less degree than any of the other primary tissues; and varied and important as the uses are which it serves in the economy, the most manifest, though certainly not the only ones, are those which depend upon its physical properties of cohesion, flexibility, extensibility, and elasticity.

1, A portion of adipose tissue; 2, minute bags containing
the fat; 3, a cluster of the bags, separated and suspended.