Biology and Its Makers / With Portraits and Other Illustrations

BIOLOGY
AND ITS MAKERS

With Portraits and Other Illustrations

BY

WILLIAM A. LOCY, Ph.D., Sc.D.

Professor in Northwestern University

NEW YORK

HENRY HOLT AND COMPANY

1908

Copyright, 1908,

BY

HENRY HOLT AND COMPANY

Published June, 1908

To MY GRADUATE STUDENTS
Who have worked by my side in the Laboratory Inspired by the belief that those who seek shall find This account of the findings of some of The great men of biological science Is dedicated by
The Author

PREFACE

The writer is annually in receipt of letters from students, teachers, ministers, medical men, and others, asking for information on topics in general biology, and for references to the best reading on that subject. The increasing frequency of such inquiries, and the wide range of topics covered, have created the impression that an untechnical account of the rise and progress of biology would be of interest to a considerable audience. As might be surmised, the references most commonly asked for are those relating to different phases of the Evolution Theory; but the fact is usually overlooked by the inquirers that some knowledge of other features of biological research is essential even to an intelligent comprehension of that theory.

In this sketch I have attempted to bring under one view the broad features of biological progress, and to increase the human interest by writing the story around the lives of the great Leaders. The practical execution of the task resolved itself largely into the question of what to omit. The number of detailed researches upon which progress in biology rests made rigid selection necessary, and the difficulties of separating the essential from the less important, and of distinguishing between men of temporary notoriety and those of enduring fame, have given rise to no small perplexities.

The aim has been kept in mind to give a picture sufficiently diagrammatic not to confuse the general reader, and it is hoped that the omissions which have seemed necessary will, in a measure, be compensated for by the clearness of the picture. References to selected books and articles have been given at the close of the volume, that will enable readers who wish fuller information to go to the best sources.

The book is divided into two sections. In the first are considered the sources of the ideas—except those of organic evolution—that dominate biology, and the steps by which they have been molded into a unified science. The Doctrine of Organic Evolution, on account of its importance, is reserved for special consideration in the second section. This is, of course, merely a division of convenience, since after its acceptance the doctrine of evolution has entered into all phases of biological progress.

The portraits with which the text is illustrated embrace those of nearly all the founders of biology. Some of the rarer ones are unfamiliar even to biologists, and have been discovered only after long search in the libraries of Europe and America.

An orderly account of the rise of biology can hardly fail to be of service to the class of inquirers mentioned in the opening paragraph. It is hoped that this sketch will also meet some of the needs of the increasing body of students who are doing practical work in biological laboratories. It is important that such students, in addition to the usual classroom instruction, should get a perspective view of the way in which biological science has come into its present form.

The chief purpose of the book will have been met if I have succeeded in indicating the sources of biological ideas and the main currents along which they have advanced, and if I have succeeded, furthermore, in making readers acquainted with those men of noble purpose whose work has created the epochs of biological history, and in showing that there has been continuity of development in biological thought.

Of biologists who may examine this work with a critical purpose, I beg that they will think of it merely as an outline sketch which does not pretend to give a complete history of biological thought. The story has been developed almost entirely from the side of animal life; not that the botanical side has been underestimated, but that the story can be told from either side, and my first-hand acquaintance with botanical investigation is not sufficient to justify an attempt to estimate its particular achievements.

The writer is keenly aware of the many imperfections in the book. It is inevitable that biologists with interests in special fields will miss familiar names and the mention of special pieces of notable work, but I am drawn to think that such omissions will be viewed leniently, by the consideration that those best able to judge the shortcomings of this sketch will also best understand the difficulties involved.

The author wishes to acknowledge his indebtedness to several publishing houses and to individuals for permission to copy cuts and for assistance in obtaining portraits. He takes this opportunity to express his best thanks for these courtesies. The parties referred to are the director of the American Museum of Natural History; D. Appleton & Co.; P. Blakiston's Sons & Co.; The Macmillan Company; The Open Court Publishing Company; the editor of the Popular Science Monthly; Charles Scribner's Sons; Professors Bateson, of Cambridge, England; Conklin, of Philadelphia; Joubin, of Rennes, France; Nierstrasz, of Utrecht, Holland; Newcombe, of Ann Arbor, Michigan; Wheeler and E.B. Wilson, of New York City. The editor of the Popular Science Monthly has also given permission to reprint the substance of Chapters IV and X, which originally appeared in that publication.

W.A.L.

Northwestern University,
Evanston, Ill., April, 1908.

CONTENTS

ILLUSTRATIONS

[1. Aristotle], 384-322 B.C.,
[2. Pliny], 23-79 A.D.,
[3. Galen,] 131-200,
[4. Vesalius,] 1514-1565,
[5. Anatomical Sketch from Vesalius' Fabrica] (1543),
[6. The Skeleton from Vesalius' Fabrica,]
[7. Initial Letters from the Fabrica,]
[8. Fallopius,] 1523-1563,
[9. Fabricius, Harvey's Teacher,] 1537-1619,
[10. William Harvey,] 1578-1657,
[11. Scheme of the Portal Circulation according to Vesalius] (1543),
[12. Hooke's Microscope] (1665),
[13. Malpighi,] 1628-1694,
[14. From Malpighi's Anatomy of the Silkworm] (1669),
[15. Swammerdam,] 1637-1680,
[16. From Swammerdam's Biblia Naturæ,]
[17. Anatomy of an Insect Dissected and Drawn by Swammerdam],
[18. Leeuwenhoek,] 1632-1723,
[19. Leeuwenhoek's Microscope],
[20a. Leeuwenhoek's Mechanism for Examining the Circulation of the Blood],
[20b. The Capillary Circulation, after Leeuwenhoek,]
[21. Plant Cells from Leeuwenhoek's Arcana Naturæ,]
[22. Lyonet,] 1707-1789,
[23. Larva of the Willow Moth, from Lyonet's Monograph] (1750),
[24. Muscles of the Larva of the Willow Moth, from Lyonet's Monograph],
[25. Central Nervous System and Nerves of the Same Animal],
[26. Dissection of the Head of the Larva of the Willow Moth],
[27. The Brain and Head Nerves of the Same Animal,]
[28. Roesel von Rosenhof,] 1705-1759,
[29. Réaumur,] 1683-1757,
[30. Nervous System of the Cockchafer, from Straus-Dürckheim's Monograph] (1828),
[31. Ehrenberg,] 1795-1876,8
[32. Gesner,] 1516-1565,
[33. John Ray,] 1628-1705,
[34. Linnæus at Sixty] (1707-1778),
[35. Karl Th. von Siebold,]
[36. Rudolph Leuckart,]
[37. Severinus,] 1580-1656,
[38. Camper,] 1722-1789,
[39. John Hunter,] 1728-1793,
[40. Vicq d'Azyr,] 1748-1794,
[41. Cuvier as a Young Man,] 1769-1829,
[42. Cuvier at the Zenith of His Power],
[43. H. Milne-Edwards], 1800-1885,
[44. Lacaze-Duthiers], 1821-1901,
[45. Lorenzo Oken,] 1779-1851,
[46. Richard Owen], 1804-1892,
[47. J. Fr. Meckel,] 1781-1833,
[48. Karl Gegenbaur,] 1826-1903,
[49. Bichat,] 1771-1801, 169
[50. Von Koelliker,] 1817-1905,
[51. Rudolph Virchow,] 1821-1903,
[52. Franz Leydig,] 1821-1908 (April),
[53. S. Ramon y Cajal,]
[54. Albrecht Haller,] 1708-1777,
[55. Charles Bell,] 1774-1842,
[56. Johannes Müller], 1801-1858,
[57. Ludwig,] 1816-1895,
[58. Du Bois-Reymond,] 1818-1896,
[59. Claude Bernard,] 1813-1878,
[60. Frontispiece of Harvey's Generatione Animalium] (1651),
[61. Selected Sketches from Malpighi's Works],
[62. Marcello Malpighi], 1628-1694,
[63. Plate from Wolff's Theoria Generationis] (1759),
[64. Charles Bonnet,] 1720-1793,
[65. Karl Ernst von Baer,] 1792-1876,
[66. Von Baer at about Seventy Years of Age,]
[67. Sketches from Von Baer's Embryological Treatise] (1828),
[68. A. Kowalevsky,] 1840-1901,
[69. Francis M. Balfour,] 1851-1882,
[70. Oskar Hertwig in 1890,]
[71. Wilhelm His,] 1831-1904,
[72. The Earliest Known Picture of Cells, from Hooke's Micrographia] (1665),
[73. Sketch from Malpighi's Treatise on the Anatomy of Plants] (1670),
[74. Theodor Schwann,] 1810-1882,
[75. M. Schleiden,] 1804-1881,
[76. The Egg and Early Stages in Its Development (after Gegenbaur)],
[77. An Early Stage in the Development of the Egg of a Rock Limpet (after Conklin)],
[78. Highly Magnified Tissue-Cells from the Skin of a Salamander (after Wilson)],
[79. Diagram of the Chief Steps in Cell-Division (after Parker)],
[80. Diagram of a Cell (modified after Wilson)],
[81. (A) Rotation of Protoplasm in Cells of Nitella.
(B) Highly Magnified Cells of a Tradescantia Plant,
Showing Circulation of Protoplasm (after Sedgwick and Wilson)],
[82. Félix Dujardin,] 1801-1860,
[83. Purkinje,] 1787-1869,
[84. Carl Nägeli], 1817-1891,
[85. Hugo von Mohl], 1805-1872,
[86. Ferdinand Cohn], 1828-1898,
[87. Heinrich Anton De Bary,] 1831-1888,
[88. Max Schultze,] 1825-1874,
[89. Francesco Redi,] 1626-1697,
[90. Lazzaro Spallanzani], 1729-1799,
[91. Apparatus of Tyndall for Experimenting on Spontaneous Generation,]
[92. Louis Pasteur (1822-1895) and His Granddaughter],
[93. Robert Koch, born 1843],
[94. Sir Joseph Lister, born 1827],
[95. Gregor Mendel,] 1822-1884,
[96. Francis Galton, born 1822],
[97. Charles Lyell,] 1797-1875,
[98. Professor Owen and the Extinct Fossil Bird of New Zealand],
[99. Louis Agassiz,] 1807-1873,
[100. E.D. Cope,] 1840-1897,
[101. O.C. Marsh,] 1831-1899,
[102. Karl von Zittel,] 1839-1904,
[103. Transmutations of Paludina (after Neumayer)],
[104. Planorbis Shells from Steinheim (after Hyatt)],
[105. Bones of the Foreleg of a Horse],
[106. Bones of Fossil Ancestors of the Horse,]
[107. Representation of the Ancestor of the Horse
Drawn by Charles R. Knight under the Direction of Professor Osborn.]
[108. Fossil Remains of a Primitive Bird (Archæopteryx)],
[109. Gill-clefts of a Shark Compared with those of the Embryonic Chick and Rabbit],
[110. Jaws of an Embryonic Whale, showing Rudimentary Teeth],
[111. Profile Reconstructions of the Skulls of Living and of Fossil Men],
[112. Lamarck,] 1744-1829,
[113. Charles Darwin,] 1809-1882,
[114. August Weismann, born 1834],
[115. Hugo de Vries],
[116. Buffon,] 1707-1788,
[117. Erasmus Darwin,] 1731-1802,
[118. Geoffroy Saint Hilaire,] 1772-1844, 416
[119. Charles Darwin,] 1809-1882,
[120. Alfred Russel Wallace, born 1823],
[121. Thomas Henry Huxley], 1825-1895,
[122. Ernst Haeckel, born 1834],
[123. The Biological Station at Naples],

[PART I]

THE SOURCES OF BIOLOGICAL IDEAS EXCEPT THOSE OF ORGANIC EVOLUTION

[CHAPTER I]

AN OUTLINE OF THE RISE OF BIOLOGY AND OF THE EPOCHS IN ITS HISTORY

"Truth is the Daughter of Time."

The nineteenth century will be for all time memorable for the great extension of the knowledge of organic nature. It was then that the results of the earlier efforts of mankind to interpret the mysteries of nature began to be fruitful; observers of organic nature began to see more deeply into the province of life, and, above all, began to see how to direct their future studies. It was in that century that the use of the microscope made known the similarity in cellular construction of all organized beings; that the substance, protoplasm, began to be recognized as the physical basis of life and the seat of all vital activities; then, most contagious diseases were traced to microscopic organisms, and as a consequence, medicine and surgery were reformed; then the belief in the spontaneous origin of life under present conditions was given up; and it was in that century that the doctrine of organic evolution gained general acceptance. These and other advances less generally known created an atmosphere in which biology—the great life-science—grew rapidly.

In the same period also the remains of ancient life, long since extinct, and for countless ages embedded in the rocks, were brought to light, and their investigation assisted materially in understanding the living forms and in tracing their genealogy.

As a result of these advances, animal organization began to have a different meaning to the more discerning naturalists, those whose discoveries began to influence the trend of thought, and finally, the idea which had been so often previously expressed became a settled conviction, that all the higher forms of life are derived from simpler ones by a gradual process of modification.

Besides great progress in biology, the nineteenth century was remarkable for similar advances in physics and chemistry. Although these subjects purport to deal with inorganic or lifeless nature, they touch biology in an intimate way. The vital processes which take place in all animals and plants have been shown to be physico-chemical, and, as a consequence, one must go to both physics and chemistry in order to understand them. The study of organic chemistry in late years has greatly influenced biology; not only have living products been analyzed, but some of them have already been constructed in the chemical laboratory. The formation of living matter through chemical means is still far from the thought of most chemists, but very complex organic compounds, which were formerly known only as the result of the action of life, have been produced, and the possibilities of further advances in that direction are very alluring. It thus appears that the discoveries in various fields have worked together for a better comprehension of nature.

The Domain of Biology.—The history of the transformation of opinion in reference to living organisms is an interesting part of the story of intellectual development. The central subject that embraces it all is biology. This is one of the fundamental sciences, since it embraces all questions relating to life in its different phases and manifestations. Everything pertaining to the structure, the development, and the evolution of living organisms, as well as to their physiology, belongs to biology. It is now of commanding importance in the world of science, and it is coming more and more to be recognized that it occupies a field of compelling interest not only for medical men and scholars, but for all intelligent people. The discoveries and conquests of biology have wrought such a revolution in thought that they should be known to all persons of liberal culture. In addition to making acquaintance with the discoveries, one ought to learn something about the history of biology; for it is essential to know how it took its rise, in order to understand its present position and the nature of its influence upon expanding ideas regarding the world in which we live.

In its modern sense, biology did not arise until about 1860, when the nature of protoplasm was first clearly pointed out by Max Schultze, but the currents that united to form it had long been flowing, and we can never understand the subject without going back to its iatric condition, when what is now biology was in the germ and united with medicine. Its separation from medicine, and its rise as an independent subject, was owing to the steady growth of that zest for exploration into unknown fields which began with the new birth of science in the sixteenth century, and has continued in fuller measure to the present. It was the outcome of applying observation and experiment to the winning of new truths.

Difficulties.—But biology is so comprehensive a field, and involves so many details, that it is fair to inquire: can its progress be made clear to the reader who is unacquainted with it as a laboratory study? The matter will be simplified by two general observations—first, that the growth of biology is owing to concurrent progress in three fields of research, concerned, respectively, with the structure or architecture of living beings, their development, and their physiology. We recognize also a parallel advance in the systematic classification of animals and plants, and we note, furthermore, that the idea of evolution permeates the whole. It will be necessary to consider the advances in these fields separately, and to indicate the union of the results into the main channel of progress. Secondly, in attempting to trace the growth of ideas in this department of learning one sees that there has been a continuity of development. The growth of these notions has not been that of a chaotic assemblage of ideas, but a well-connected story in which the new is built upon the old in orderly succession. The old ideas have not been completely superseded by the new, but they have been molded into new forms to keep pace with the advance of investigation. In its early phases, the growth of biology was slow and discursive, but from the time of Linnæus to Darwin, although the details were greatly multiplied, there has been a relatively simple and orderly progress.

Facts and Ideas.—There are many books about biology, with directions for laboratory observation and experiment, and also many of the leading facts of the science have been given to the public, but an account of the growth of the ideas, which are interpretations of the facts, has been rarely attempted. From the books referred to, it is almost impossible to get an idea of biology as a unit; this even the students in our universities acquire only through a coherent presentation of the subject in the classroom, on the basis of their work in the laboratory. The critical training in the laboratory is most important, but, after all, it is only a part, although an essential part, of a knowledge of biology. In general, too little attention is paid to interpretations and the drill is confined to a few facts. Now, the facts are related to the ideas of the science as statistics to history—meaningless without interpretation. In the rise of biology the facts have accumulated constantly, through observation and experiment, but the general truths have emerged slowly and periodically, whenever there has been granted to some mind an insight into the meaning of the facts. The detached facts are sometimes tedious, the interpretations always interesting.

The growth of the knowledge of organic nature is a long story, full of human interest. Nature has been always the same, but the capacity of man as its interpreter has varied. He has had to pass through other forms of intellectual activity, and gradually to conquer other phases of natural phenomena, before entering upon that most difficult task of investigating the manifestations of life. It will be readily understood, therefore, that biology was delayed in its development until after considerable progress had been made in other sciences.

It is an old saying that "Truth is the daughter of Time," and no better illustration of it can be given than the long upward struggle to establish even the elemental truths of nature. It took centuries to arrive at the conception of the uniformity of nature, and to reach any of those generalizations which are vaguely spoken of as the laws of nature.

The Men of Science.—In the progress of science there is an army of observers and experimenters each contributing his share, but the rank and file supply mainly isolated facts, while the ideas take birth in the minds of a few gifted leaders, either endowed with unusual insight, or so favored by circumstances that they reach general conclusions of importance. These advance-guards of intellectual conquest we designate as founders. What were they like in appearance? Under what conditions did they work, and what was their chief aim? These are interesting questions which will receive attention as our narrative proceeds.

A study of the lives of the founders shows that the scientific mood is pre-eminently one of sincerity. The men who have added to the growth of science were animated by an unselfish devotion to truth, and their lasting influence has been in large measure a reflection of their individual characters. Only those have produced permanent results who have interrogated nature in the spirit of devotion to truth and waited patiently for her replies. The work founded on selfish motives and vanity has sooner or later fallen by the wayside. We can recognize now that the work of scientific investigation, subjected to so much hostile criticism as it appeared from time to time, was undertaken in a reverent spirit, and was not iconoclastic, but remodelling in its influence. Some of the glories of our race are exhibited in the lives of the pioneers in scientific progress, in their struggles to establish some great truth and to maintain intellectual integrity.

The names of some of the men of biology, such as Harvey, Linnæus, Cuvier, Darwin, Huxley, and Pasteur, are widely known because their work came before the people, but others equally deserving of fame on account of their contributions to scientific progress will require an introduction to most of our readers.

In recounting the story of the rise of biology, we shall have occasion to make the acquaintance of this goodly company. Before beginning the narrative in detail, however, we shall look summarily at some general features of scientific progress and at the epochs of biology.

The Conditions under which Science Developed

In a brief sketch of biology there is relatively little in the ancient world that requires notice except the work of Aristotle and Galen; but with the advent of Vesalius, in 1543, our interest begins to freshen, and, thereafter, through lean times and fat times there is always something to command our attention.

The early conditions must be dealt with in order to appreciate what followed. We are to recollect that in the ancient world there was no science of biology as such; nevertheless, the germ of it was contained in the medicine and the natural history of those times.

There is one matter upon which we should be clear: in the time of Aristotle nature was studied by observation and experiment. This is the foundation of all scientific advancement. Had conditions remained unchanged, there is reason to believe that science would have developed steadily on the basis of the Greek foundation, but circumstances, to be spoken of later, arose which led not only to the complete arrest of inquiry, but also, the mind of man being turned away from nature, to the decay of science.

Aristotle the Founder of Natural History.—The Greeks represented the fullest measure of culture in the ancient world, and, naturally, we find among them the best-developed science. All the knowledge of natural phenomena centered in Aristotle (384-322 B.C.), and for twenty centuries he represented the highest level which that kind of knowledge had attained.

It is uncertain how long it took the ancient observers to lift science to the level which it had at the beginning of Aristotle's period, but it is obvious that he must have had a long line of predecessors, who had accumulated facts of observation and had molded them into a system before he perfected and developed that system. We are reminded that all things are relative when we find Aristotle referring to the ancients; and well he might, for we have indubitable evidence that much of the scientific work of antiquity has been lost. One of the most striking discoveries pointing in that direction is the now famous papyrus which was found by Georg Ebers in Egypt about 1860. The recent translation of this ancient document shows that it was a treatise on medicine, dating from the fifteenth century B.C. At this time the science of medicine had attained an astonishingly high grade of development among that people. And since it is safe to assume that the formulation of a system of medicine in the early days of mankind required centuries of observation and practice, it becomes apparent that the manuscript in question was no vague, first attempt at reducing medicine to a system. It is built upon much scientific knowledge, and must have been preceded by writings both on medicine and on its allied sciences.

It is not necessary that we should attempt to picture the crude beginnings of the observation of animated nature and the dawning of ideas relative to animals and plants; it is suitable to our purpose to commence with Aristotle, and to designate him, in a relative sense, as the founder of natural history.

That he was altogether dissatisfied with the state of knowledge in his time and that he had high ideals of the dignity of science is evidenced in his writings. Although he refers to the views of the ancients, he regarded himself in a sense as a pioneer. "I found no basis prepared," he says, "no models to copy.... Mine is the first step, and therefore a small one, though worked out with much thought and hard labor. It must be looked at as a first step and judged with indulgence." (From Osborn's From the Greeks to Darwin.)

There is general agreement that Aristotle was a man of vast intellect and that he was one of the greatest philosophers of the ancient world. He has had his detractors as well as his partisan adherents. Perhaps the just estimate of his attainments and his position in the history of science is between the enthusiastic appreciation of Cuvier and the critical estimate of Lewes.

This great man was born in Stagira in the year 384 B.C., and lived until 322 B.C. He is to be remembered as the most distinguished pupil of Plato, and as the instructor of Alexander the Great. Like other scholars of his time, he covered a wide range of subjects; we have mention, indeed, of about three hundred works of his composition, many of which are lost. He wrote on philosophy, metaphysics, psychology, politics, rhetoric, etc., but it was in the domain of natural history that he attained absolute pre-eminence.

His Position in the Development of Science.—It is manifestly unjust to measure Aristotle by present standards; we must keep always in mind that he was a pioneer, and that he lived in an early day of science, when errors and crudities were to be expected. His greatest claim to eminence in the history of science is that he conceived the things of importance and that he adopted the right method in trying to advance the knowledge of the natural universe. In his program of studies he says: "First we must understand the phenomena of animals; then assign their causes; and, finally, speak of their generation." His position in natural history is frequently misunderstood. One of the most recent writers on the history of science, Henry Smith Williams, pictures him entirely as a great classifier, and as the founder of systematic zoölogy. While it is true that he was the founder of systematic zoölogy, as such he did not do his greatest service to natural history, nor does the disposition to classify represent his dominant activity. In all his work classification is made incidental and subservient to more important considerations. His observations upon structure and development, and his anticipation of the idea of organic evolution, are the ones upon which his great fame rests. He is not to be remembered as a man of the type of Linnæus; rather is he the forerunner of those men who looked deeper than Linnæus into the structure and development of animal life—the morphologists.

Particular mention of his classification of animals will be found in the chapter on Linnæus, while in what follows in this chapter attention will be confined to his observation of their structure and development and to the general influence of his work.

His great strength was in a philosophical treatment of the structure and development of animals. Professor Osborn in his interesting book, From the Greeks to Darwin, shows that Aristotle had thought out the essential features of evolution as a process in nature. He believed in a complete gradation from the lowest organisms to the highest, and that man is the highest point of one long and continuous ascent.

His Extensive Knowledge of Animals.—He made extensive studies of life histories. He knew that drone bees develop without previous fertilization of the eggs (by parthenogenesis); that in the squid the yolk sac of the embryo is carried in front of the mouth; that some sharks develop within the egg-tube of the mother, and in some species have a rudimentary blood-connection resembling the placenta of mammals. He had followed day by day the changes in the chick within the hen's egg, and observed the development of many other animals. In embryology also, he anticipated Harvey in appreciating the true nature of development as a process of gradual building, and not as the mere expansion of a previously formed germ. This doctrine, which is known under the name of epigenesis, was, as we shall see later, hotly contested in the eighteenth century, and has a modified application at the present time.

In reference to the structure of animals he had described the tissues, and in a rude way analyzed the organs into their component parts. It is known, furthermore, that he prepared plates of anatomical figures, but, unfortunately, these have been lost.

In estimating the contributions of ancient writers to science, it must be remembered that we have but fragments of their works to examine. It is, moreover, doubtful whether the scientific writings ascribed to Aristotle were all from his hand. The work is so uneven that Huxley has suggested that, since the ancient philosophers taught viva voce, what we have of his zoölogical writings may possibly be the notes of some of his students. While this is not known to be the case, that hypothesis enables us to understand the intimate mixture of profound observation with trivial matter and obvious errors that occur in the writings ascribed to him.

Hertwig says: "It is a matter for great regret that there have been preserved only parts of his three most important zoölogical works, 'Historia animalium,' 'De partibus,' and 'De generatione,' works in which zoölogy is founded as a universal science, since anatomy and embryology, physiology and classification, find equal consideration."

Some Errors.—Dissections were little practised in his day, and it must be admitted that his observations embrace many errors. He supposed the brain to be bloodless, the arteries to carry air, etc., but he has been cleared by Huxley of the mistake so often attributed to him of supposing the heart of mammals to have only three chambers. It is altogether probable that he is credited with a larger number of errors than is justified by the facts.

He must have had unusual gifts in the exposition of these technical subjects; indeed, he made his researches appear so important to his royal patron, Alexander, that he was aided in the preparation of his great Natural History by a grant of 800 talents (equivalent to $200,000) and by numerous assistants and collectors. Thus in ancient times was anticipated the question that is being agitated to-day—that of the support and the endowment of research.

Personal Appearance.—Some idea of his looks may be gained from Fig. 1. This is a copy of a bas-relief found in the collection of Fulvius Ursinus (d. 1600), and was originally published by J. Faber. Its authenticity as a portrait is attested (1811) by Visconti, who says that it has a perfect resemblance to the head of a small bust upon the base of which the name of Aristotle is engraved. Portrait busts and statues of Aristotle were common in ancient times. The picture of him most familiar to general readers is the copy of the head and shoulders of an ancient statue representing him with a draping over the left shoulder. This is an attractive portrait, showing a face of strong intellectuality. Its authenticity, however, is not as well established as that of the picture shown here. Other pictures, believed to be those of Aristotle, represent him later in life with receding hair, and one exists in which his baldness is very extensive. He was described as short in stature, with spindling legs and small, penetrating eyes, and to have been, in his younger days, vain and showy in his dress.

He was early left an orphan with a considerable fortune; and there are stories of early excesses after coming into his property. These charges, however, lack trustworthy support, and are usually regarded as due mainly to that undermining gossip which follows one holding prominent place and enviable recognition. His habits seem to have been those of a diligent student with a zest in his work; he was an omnivorous reader, and Plato called him the mind of his school. His large private library and his manner of living bespeak the conserving of his property, rather than its waste in selfish indulgences.

Fig. 1.—Aristotle, 384-322 B.C.

His Influence.—The influence of Aristotle was in the right direction. He made a direct appeal to nature for his facts, and founded his Natural History only on observation of the structure, physiology, and development of animals. Unfortunately, the same cannot be said of his successors.

Galen, who is mentioned above in connection with Aristotle, was a medical writer and the greatest anatomist of antiquity. On account of the relation of his work to the growth of anatomy, however, the consideration of it is reserved for the chapter on Vesalius.

Soon after the period of Aristotle the center of scientific investigation was transferred to Alexandria, where Ptolemy had erected a great museum and founded a large public library. Here mathematics and geography flourished, but natural history was little cultivated.

In order to find the next famous naturalist of antiquity, it is necessary to look to Rome. Rome, although great in political power, never became a true culture center, characterized by originality. All that remains of their thought shows us that the Roman people were not creative. In the capital of the empire, the center of its life, there arose no great scientific investigator.

Fig. 2.—Pliny, 23-79 A.D.

Pliny.—The situation is represented by Pliny the Elder (23-79 A.D.), Roman general and littérateur (Fig. 2). His works on natural history, filling thirty-seven volumes, have been preserved with greater completeness than those of other ancient writers. Their overwhelming bulk seems to have produced an impression upon those who, in the nineteenth century, heralded him as the greatest naturalist of antiquity. But an examination of his writings shows that he did nothing to deepen or broaden the knowledge of nature, and his Natural History marks a distinct retrograde movement. He was, at best, merely a compiler—"a collector of anecdotes"—who, forsaking observation, indiscriminately mixed fable, fact, and fancy taken from the writings of others. He emphasized the feature of classification which Aristotle had held in proper subordination, and he replaced the classification of Aristotle, founded on plan of organization, by a highly artificial one, founded on the incidental circumstance of the abodes of animals—either in air, water, or on the earth.

The Arrest of Inquiry and its Effects.—Thus, natural history, transferred from a Greek to a Roman center, was already on the decline in the time of Pliny; but it was destined to sink still lower. It is an old, oft-repeated story how, with the overthrow of ancient civilization, the torch of learning was nearly extinguished. Not only was there a complete political revolution; there was also a complete change in the mental interests of mankind. The situation is so complex that it is difficult to state it with clearness. So far as science is concerned, its extinction was due to a turning away from the external world, and a complete arrest of inquiry into the phenomena of nature. This was an important part of that somber change which came over all mental life.

One of the causes that played a considerable part in the cessation of scientific investigation was the rise of the Christian church and the dominance of the priesthood in all intellectual as well as in spiritual life. The world-shunning spirit, so scrupulously cultivated by the early Christians, prompted a spirit which was hostile to observation. The behest to shun the world was acted upon too literally. The eyes were closed to nature and the mind was directed toward spiritual matters, which truly seemed of higher importance. Presently, the observation of nature came to be looked upon as proceeding from a prying and impious curiosity.

Books were now scarcer than during the classical period; the schools of philosophy were reduced, and the dissemination of learning ceased. The priests who had access to the books assumed direction of intellectual life. But they were largely employed with the analysis of the supernatural, without the wholesome check of observation and experiment; mystical explanations were invented for natural phenomena, while metaphysical speculation became the dominant form of mental activity.

Authority Declared the Source of Knowledge.—In this atmosphere controversies over trivial points were engendered, and the ancient writings were quoted as sustaining one side or the other. All this led to the referring of questions as to their truth or error to authority as the source of knowledge, and resulted in a complete eclipse of reason. Amusing illustrations of the situation are abundant; as when, in the Middle Ages, the question of the number of teeth in the horse was debated with great heat in many contentious writings. Apparently none of the contestants thought of the simple expedient of counting them, but tried only to sustain their position by reference to authority. Again, one who noticed spots on the sun became convinced of the error of his eyes because Aristotle had somewhere written "The face of the sun is immaculate."

This was a barren period not only for science, but also for ecclesiastical advance. Notwithstanding the fact that for more than a thousand years the only new works were written by professional theologians, there was no substantial advance in their field, and we cannot escape the reflection that the reciprocal action of free inquiry is essential to the growth of theology as of other departments of learning.

In the period from the downfall of Rome to the revival of learning, one eminent theologian, St. Augustine, stands in relief for the openness of his mind to new truth and for his expressions upon the relation of revelation in the Scriptures to the observation of nature. His position will be more clearly indicated in the chapter dealing with the rise of evolutionary thought.

Perhaps it has been the disposition of historians to paint the Middle Ages in too dark colors in order to provide a background on which fitly to portray the subsequent awakening. It was a remolding period through which it was necessary to pass after the overthrow of ancient civilization and the mixture of the less advanced people of the North with those of the South. The opportunities for advance were greatly circumscribed; the scarcity of books and the lack of facilities for travel prevented any general dissemination of learning, while the irresponsible method of the time, of appealing to authority on all questions, threw a barrier across the stream of progress. Intellectuality was not, however, entirely crushed during the prevalence of these conditions. The medieval philosophers were masters of the metaphysical method of argument, and their mentality was by no means dull. While some branches of learning might make a little advance, the study of nature suffered the most, for the knowledge of natural phenomena necessitates a mind turned outward in direct observation of the phenomena of the natural and physical universe.

Renewal of Observation.—It was an epoch of great importance, therefore, when men began again to observe, and to attempt, even in an unskilful way, hampered by intellectual inheritance and habit, to unravel the mysteries of nature and to trace the relation between causes and effects in the universe. This new movement was a revolt of the intellect against existing conditions. In it were locked up all the benefits that have accrued from the development of modern science. Just as the decline had been due to many causes, so also the general revival was complex. The invention of printing, the voyages of mariners, the rise of universities, and the circulation of ideas consequent upon the Crusades, all helped to disseminate the intellectual ferment. These generic influences aided in molding the environment, but, just as the pause in science had been due to the turning away from nature and to new mental interests, so the revival was a return to nature and to the method of science. The pioneers had to be men of determined independence; they labored against self-interest as well as opposition from the church and the priesthood, and they withstood the terrors of the Inquisition and the loss of recognition and support.

In this uncongenial atmosphere men like Galileo, Descartes, and Vesalius established the new movement and overthrew the reign of authority. With the coming of Vesalius the new era of biological progress was opened, but its growth was a slow one; a growth of which we are now to be concerned in tracing the main features.

The Epochs in Biological History

It will be helpful to outline the great epochs of biological progress before taking them up for fuller consideration. The foundation of progress was the renewal of observation in which, as already stated, all modern science was locked up.

It was an epoch in biological history when Vesalius overthrew the authority of Galen, and studied at first hand the organization of the human body.

It was an epoch when William Harvey, by adding experiment to observation, demonstrated the circulation of the blood and created a new physiology. The two coördinate branches of biology were thus early outlined.

The introduction of the microscope, mainly through the labors of Grew, Hooke, Malpighi, and Leeuwenhoek, opened a new world to the investigator, and the work of these men marks an epoch in the progress of independent inquiry.

Linnæus, by introducing short descriptions and uniform names for animals and plants, greatly advanced the subject of natural history.

Cuvier, by founding the school of comparative anatomy, so furthered the knowledge of the organization of animals that he created an epoch.

Bichat, his great contemporary, created another by laying the foundation of our knowledge of the structure of animal tissues.

Von Baer, by his studies of the development of animal life, supplied what was lacking in the work of Cuvier and Bichat and originated modern embryology.

Haller, in the eighteenth, and Johannes Müller in the nineteenth century, so added to the ground work of Harvey that physiology was made an independent subject and was established on modern lines.

With Buffon, Erasmus Darwin,, and Lamarck began an epoch in evolutionary thought which had its culminating point in the work of Charles Darwin.

After Cuvier and Bichat came the establishing of the cell-theory, which created an epoch and influenced all further progress.

Finally, through the discovery of protoplasm and the recognition that it is the seat of all vital activity, arrived the epoch which brought us to the threshold of the biology of the present day.

Step by step naturalists have been led from the obvious and superficial facts about living organisms to the deep-lying basis of all vital manifestations.

[CHAPTER II]

VESALIUS AND THE OVERTHROW OF AUTHORITY IN SCIENCE

Vesalius, although an anatomist, is to be recognized in a broad sense as one of the founders of biology. When one is attempting to investigate animal and plant life, not only must he become acquainted with the external appearance of living organisms, but also must acquire early a knowledge of their structure, without which other facts relating to their lives can not be disclosed. Anatomy, which is the science of the structure of organized beings, is therefore so fundamental that we find ourselves involved in tracing the history of its rise as one part of the story of biology. But it is not enough to know how animals and plants are constructed; we must also know something about the purpose of the structures and of the life that courses through them, and, accordingly, after considering the rise of anatomy, we must take a similar view of its counterpart, physiology.

The great importance of Vesalius in the history of science lies in the fact that he overthrew adherence to authority as the method of ascertaining truth, and substituted therefor observation and reason. Several of his forerunners had tried to accomplish the same end, but they had failed. He was indebted to them as every man is indebted to his forebears, but at the same time we can not fail to see that Vesalius was worthy of the victory. He was more resolute and forceful than any of his predecessors. He was one of those rare spirits who see new truth with clearness, and have the bravery to force their thoughts on an unsympathetic public.

The Beginning of Anatomy.—In order to appreciate his service it is necessary to give a brief account of his predecessors, and of the condition of anatomy in his time. Remembering that anatomy embraces a knowledge of the architecture of all animals and plants, we can, nevertheless, see why in early times its should have had more narrow boundaries. The medical men were the first to take an interest in the structure of the human body, because a knowledge of it is necessary for medicine and surgery. It thus happens that the earliest observations in anatomy were directed toward making known the structure of the human body and that of animals somewhat closely related to man in point of structure. Anatomical studies, therefore, began with the more complex animals instead of the simpler ones, and, later, when comparative anatomy began to be studied, this led to many misunderstandings; since the structure of man became the type to which all others were referred, while, on account of his derivation, his structure presents the greatest modification of the vertebrate type.

It was so difficult in the early days to get an opportunity to study the human body that the pioneer anatomists were obliged to gain their knowledge by dissections of animals, as the dog, and occasionally the monkey. In this way Aristotle and his forerunners learned much about anatomy. About 300 B.C., the dissection of the human body was legalized in the Alexandrian school, the bodies of condemned criminals being devoted to that purpose. But this did not become general even for medical practitioners, and anatomy continued to be studied mainly from brute animals.

Galen.—The anatomist of antiquity who outshines all others was Galen (Claudius Galenus, 130-200 A.D.), who lived some time in Pergamos, and for five years in Rome, during the second century of the Christian era. He was a man of much talent, both as an observer and as a writer. His descriptions were clear and forceful, and for twelve centuries his works exerted the greatest influence of those of all scientific writers. In his writings was gathered all the anatomical knowledge of his predecessors, to which he had added observations of his own. He was a man of originality, but not having the human body for dissection, he erred in expounding its structure "on the faith of observations made on lower animals." He used the right method in arriving at his facts. Huxley says: "No one can read Galen's works without being impressed with the marvelous extent and diversity of his knowledge, and by his clear grasp of those experimental methods by which alone physiology can be advanced."

Anatomy in the Middle Ages.—But now we shall see how the arrest of inquiry already spoken of operated in the field of anatomy. The condition of anatomy in the Middle Ages was the condition of all science in the same period. From its practical importance anatomy had to be taught to medical men, while physics and chemistry, biology and comparative anatomy remained in an undeveloped state. The way in which this science was taught is a feature which characterizes the intellectual life of the Middle Ages. Instead of having anatomy taught by observations, the writings of Galen were expounded from the desk, frequently without demonstrations of any kind. Thus his work came to be set up as the one unfailing authority on anatomical knowledge. This was in accord with the dominant ecclesiastical influence of the time. Reference to authority was the method of the theologians, and by analogy it became the method of all learning. As the Scriptures were accepted as the unfailing guide to spiritual truth, so Galen and other ancient writers were made the guides to scientific truth and thought. The baneful effects of this in stifling inquiry and in reducing knowledge to parrot-like repetition of ancient formulas are so obvious that they need not be especially dwelt upon.

Fig. 3.—Galen, 131-200.
From Acta Medicorum Berolinensium, 1715.

Predecessors of Vesalius.—Italy gave birth to the first anatomists who led a revolt against this slavery to authority in scientific matters. Of the eminent anatomists who preceded Vesalius it will be necessary to mention only three. Mundinus, or Mondino, professor at the University of Bologna, who, in the early part of the fourteenth century, dissected three bodies, published in 1315 a work founded upon human dissection. He was a man of originality whose work created a sensation in the medical world, but did not supersede Galen's. His influence, although exerted in the right direction, was not successful in establishing observation as the method of teaching anatomy. His book, however, was sometimes used as an introduction to Galen's writings or in conjunction with them.

The next man who requires notice is Berengarius of Carpi, who was a professor in the University of Bologna in the early part of the sixteenth century. He is said to have dissected not less than one hundred human bodies; and although his opportunities for practical study were greater than those of Mondino, his attempts to place the science of anatomy upon a higher level were also unsuccessful.

We pass now from Italy to France, where Sylvius (1478-1555), one of the teachers of Vesalius, made his mark. His name is preserved to-day in the fissure of Sylvius in the brain, but he was not an original investigator, and he succeeded only in "making a reputation to which his researches do not entitle him." He was a selfish, avaricious man whose adoption of anatomy was not due to scientific interest, but to a love of gain. At the age of fifty he forsook the teaching of the classics for the money to be made by teaching anatomy. He was a blind admirer of Galen, and read his works to medical students without dissections, except that from time to time dogs were brought into the amphitheater and their structure exposed by unskilled barbers.

Vesalius.—Vesalius now came upon the scene; and through his efforts, before he was thirty years of age, the idol of authority had been shattered, and, mainly through his persistence, the method of so great moment to future ages had been established. He was well fitted to do battle against tradition—strong in body, in mind, and in purpose, gifted and forceful; and, furthermore, his work was marked by concentration and by the high moral quality of fidelity to truth.

Vesalius was born in Brussels on the last day of the year 1514, of an ancestry of physicians and learned men, from whom he inherited his leaning toward scientific pursuits. Early in life he exhibited a passion for anatomy; he dissected birds, rabbits, dogs, and other animals. Although having a strong bent in this direction, he was not a man of single talent. He was schooled in all the learning of his time, and his earliest publication was a translation from the Greek of the ninth book of Rhazes. After his early training at Brussels and at the University of Louvain, in 1533, at the age of 18, he went to Paris to study medicine, where, in anatomy, he came under Sylvius and Günther.

His Force and Independence.—His impetuous nature was shown in the amphitheatre of Sylvius, where, at the third lecture, he pushed aside the clumsy surgeon barbers, and himself exposed the parts as they should be. He could not be satisfied with the exposition of the printed page; he must see with his own eyes, must grasp through his own experience the facts of anatomical structure. This demand of his nature shows not only how impatient he was with sham, but also how much more he was in touch with reality than were the men of his time.

After three years at the French capital, owing to wars in Belgium, he went back to Louvain without obtaining his medical degree. After a short experience as surgeon on the field of battle, he went to Padua, whither he was attracted by reports of the opportunities for practical dissection that he so much desired to undertake. There his talents were recognized, and just after receiving his degree of Doctor of Medicine in 1537, he was given a post in surgery, with the care of anatomy, in the university.

His Reform of the Teaching of Anatomy.—The sympathetic and graphic description of this period of his career by Sir Michael Foster is so good that I can not refrain from quoting it: "He at once began to teach anatomy in his own new way. Not to unskilled, ignorant barbers would he entrust the task of laying bare before the students the secrets of the human frame; his own hand, and his own hand alone, was cunning enough to track out the pattern of the structures which day by day were becoming more clear to him. Following venerated customs, he began his academic labors by 'reading' Galen, as others had done before him, using his dissections to illustrate what Galen had said. But, time after time, the body on the table said something different from that which Galen had written.

"He tried to do what others had done before him—he tried to believe Galen rather than his own eyes, but his eyes were too strong for him; and in the end he cast Galen and his writings to the winds, and taught only what he himself had seen and what he could make his students see, too. Thus he brought into anatomy the new spirit of the time, and the men of the time, the young men of the time, answered the new voice. Students flocked to his lectures; his hearers amounted, it is said, to some five hundred, and an enlightened senate recognized his worth by repeatedly raising his emoluments.

Fig. 4.—Vesalius, 1514-1564.

"Five years he thus spent in untiring labors at Padua. Five years he wrought, not weaving a web of fancied thought, but patiently disentangling the pattern of the texture of the human body, trusting to the words of no master, admitting nothing but that which he himself had seen; and at the end of the five years, in 1542, while he was as yet not twenty-eight years of age, he was able to write the dedication to Charles V of a folio work entitled the 'Structure of the Human Body,' adorned with many plates and woodcuts which appeared at Basel in the following year, 1543."

His Physiognomy.—This classic with the Latin title, De Humani Corporis Fabrica, requires some special notice; but first let us have a portrait of Vesalius, the master. Fig. 4 shows a reproduction of the portrait with which his work is provided. He is represented in academic costume, probably that which he wore at lectures, in the act of demonstrating the muscles of the arm. The picture is reduced, and in the reduction loses something of the force of the original. We see a strong, independent, self-willed countenance; what his features lack in refinement they make up in force; not an artistic or poetic face, but the face of the man of action with scholarly training.

His Great Book.—The book of Vesalius laid the foundation of modern biological science. It is more than a landmark in the progress of science—it created an epoch. It is not only interesting historically, but on account of the highly artistic plates with which it is illustrated it is interesting to examine by one not an anatomist. For executing the plates Vesalius secured the service of a fellow-countryman, John Stephen de Calcar, who was one of the most gifted pupils of Titian. The drawings are of such high artistic quality that for a long time they were ascribed to Titian. The artist has attempted to soften the necessarily prosaic nature of anatomical illustrations by introducing an artistic background of landscape of varied features, with bridges, roads, streams, buildings, etc. The employment of a background even in portrait-painting was not uncommon in the same century, as in Leonardo da Vinci's well-known Mona Lisa, with its suggestive perspective of water, rocks, etc.

Fig. 5.—Anatomical Sketch from Vesalius's Fabrica.
(Photographed and reduced from the facsimile edition of 1728.)

Fig. 5 will give an idea on a small scale of one of the plates illustrating the work of Vesalius. The plates in the original are of folio size, and represent a colossal figure in the foreground, with a background showing between the limbs and at the sides of the figure. There is considerable variety as regards the background, no two plates being alike.

Also, in delineating the skeleton, the artist has given to it an artistic pose, as is shown in Fig. 6, but nevertheless the bones are well drawn. No plates of equal merit had appeared before these; in fact, they are the earliest generally known drawings in anatomy, although woodcuts representing anatomical figures were published as early as 1491 by John Ketham. Ketham's figures showed only externals and preparations for opening the body, but rude woodcuts representing internal anatomy and the human skeleton had been published notably by Magnus Hundt, 1501; Phrysen, 1518; and Berengarius, 1521 and 1523. Leonardo da Vinci and other artists had also executed anatomical drawings before the time of Vesalius.

Previous to the publication of the complete work, Vesalius, in 1538, had published six tables of anatomy, and, in 1555, he brought out a new edition of the Fabrica, with slight additions, especially in reference to physiology, which will be adverted to in the chapter on Harvey.

Fig. 6.—The Skeleton, from Vesalius's Fabrica.

In the original edition of 1543 the illustrations are not collected in the form of plates, but are distributed through the text, the larger ones making full-page (folio) illustrations. In this edition also the chapters are introduced with an initial letter showing curious anatomical figures in miniature, some of which are shown in Fig. 7.

Fig. 7.—Initial letters from Vesalius's Fabrica of 1543.

The Fabrica of Vesalius was a piece of careful, honest work, the moral influence of which must not be overlooked. At any moment in the world's history, work marked by sincerity exercises a wholesome influence, but at this particular stage of intellectual development such work was an innovation, and its significance for progress was wider and deeper than it might have been under different circumstances.

Opposition to Vesalius.—The beneficent results of his efforts were to unfold afterward, since, at the time, his utterances were vigorously opposed from all sides. Not only did the ecclesiastics contend that he was disseminating false and harmful doctrine, but the medical men from whom he might have expected sympathy and support violently opposed his teachings.

Many amusing arguments were brought forward to discredit Vesalius, and to uphold the authority of Galen. Vesalius showed that in the human body the lower jaw is a single bone—that it is not divided as it is in the dog and other lower mammals, and, as Galen had taught, also in the human subjects. He showed that the sternum, or breast bone, has three parts instead of eight; he showed that the thigh bones are straight and not curved, as they are in the dog. Sylvius, his old teacher, was one of his bitterest opponents; he declared that the human body had undergone changes in structure since the time of Galen, and, with the object of defending the ancient anatomist, "he asserted that the straight thigh bones, which, as every one saw, were not curved in accordance with the teaching of Galen, were the result of the narrow trousers of his contemporaries, and that they must have been curved in their natural condition, when uninterfered with by art!"

The theologians also found other points for contention. It was a widely accepted dogma that man should have one less rib on one side, because from the Scriptural account Eve was formed from one of Adam's ribs. This, of course, Vesalius did not find to be the case. It was also generally believed at this time that there was in the body an indestructible resurrection-bone which formed the nucleus of the resurrection-body. Vesalius said that he would leave the question of the existence of such a bone to be decided by the theologians, as it did not appear to him to be an anatomical question.

The Court Physician.—The hand of the church was heavy upon him, and the hatred shown in attacks from various quarters threw Vesalius into a state of despondency and anger. In this frame of mind he destroyed manuscripts upon which he had expended much labor. His disappointment in the reception of his work probably had much to do in deciding him to relinquish his professorship and accept the post of court physician to Charles V of the United Kingdoms of Spain and Belgium. After the death of Charles, he remained with Philip II, who succeeded to the throne. Here he waxed rich and famous, but he was always under suspicion by the clerical powers, who from time to time found means of discrediting him. The circumstances of his leaving Spain are not definitely known. One account has it that he made a post-mortem examination of a body which showed signs of life during the operation, and that he was required to undertake a pilgrimage to the Holy Land to clear his soul of sacrilege. Whether or not this was the reason is uncertain, but after nineteen years at the Spanish Court he left, in 1563, and journeyed to Jerusalem. On his return from Palestine he suffered shipwreck and died from the effects of exposure on Zanti, one of the Ionian Islands. It is also said that while on this pilgrimage he had been offered the position of professor of anatomy as successor to Fallopius, who had died in 1563, and that, had he lived, he would have come back honorably to his old post.

Eustachius and Fallopius.—The work of two of his contemporaries, Eustachius and Fallopius, requires notice. Cuvier says in his Histoire des Sciences Naturelles that those three men were the founders of modern anatomy. Vesalius was a greater man than either of the other two, and his influence was more far-reaching. He reformed the entire field of anatomy, while the names of Eustachius and Fallopius are connected especially with a smaller part of the field. Eustachius described the Eustachian tube of the ear and gave especial attention to sense organs; Fallopius made special investigations upon the viscera, and described the Fallopian tube.

Fallopius was a suave, polite man, who became professor of anatomy at Padua; he opposed Vesalius, but his attacks were couched in respectful terms.

Eustachius, the professor of anatomy at Rome, was of a different type, a harsh, violent man, who assailed Vesalius with virulence. He corrected some mistakes of Vesalius, and prepared new plates on anatomy, which, however, were not published until 1754, and therefore did not exert the influence upon anatomical studies that those of Vesalius did.

Fig. 8.—Fallopius, 1523-1563.

The Especial Service of Vesalius.—It should be remembered that both these men had the advantage of the sketches made under the direction of Vesalius. Pioneers and path-breakers are under special limitations of being in a new territory, and make more errors than they would in following another's survey of the same territory; it takes much less creative force to correct the errors of a first survey than to make the original discoveries. Everything considered, Vesalius is deserving of the position assigned to him. He was great in a larger sense, and it was his researches in particular which re-established scientific method and made further progress possible. His errors were corrected, not by an appeal to authority, but by the method which he founded. His great claim to renown is, not that his work outshone all other work (that of Galen in particular) in accuracy and brilliancy, but that he overthrew dependence on authority and re-established the scientific method of ascertaining truth. It was the method of Aristotle and Galen given anew to the world.

The spirit of progress was now released from bondage, but we have still a long way to go under its guidance to reach the gateway of modern biology.

[CHAPTER III]

WILLIAM HARVEY AND EXPERIMENTAL OBSERVATION

After the splendid observations of Vesalius, revealing in a new light the construction of the human body, Harvey took the next general step by introducing experiment to determine the use or purpose of the structures that Vesalius had so clearly exposed. Thus the work of Harvey was complemental to that of Vesalius, and we may safely say that, taken together, the work of these two men laid the foundations of the modern method of investigating nature. The results they obtained, and the influence of their method, are of especial interest to us in the present connection, inasmuch as they stand at the beginning of biological science after the Renaissance. Although the observations of both were applied mainly to the human body, they served to open the entire field of structural studies and of experimental observations on living organisms.

Many of the experiments of Harvey, notably those relating to the movements of the heart, were, of course, conducted upon the lower animals, as the frog, the dog, etc. His experiments on the living human body consisted mainly in applying ligatures to the arms and the legs. Nevertheless, the results of all his experiments related to the phenomena of the circulation in the human body, and were primarily for the use of medical men.

In what sense the observations of the two men were complemental will be better understood when we remember that there are two aspects in which living organisms should always be considered in biological studies; first, the structure, and, then, the use that the structures subserve. One view is essential to the other, and no investigation of animals and plants is complete in which the two ideas are not involved. Just as a knowledge of the construction of a machine is necessary to understand its action, so the anatomical analysis of an organ must precede a knowledge of its office. The term "physiological anatomy of an organ," so commonly used in text-books on physiology, illustrates the point. We can not appreciate the work of such an organ as the liver without a knowledge of the arrangement of its working units. The work of the anatomist concerns the statics of the body, that of the physiologist the dynamics; properly combined, they give a complete picture of the living organism.

It is to be remembered that the observations of Vesalius were not confined exclusively to structure; he made some experiments and some comments on the use of parts of the body, but his work was mainly structural, while that which distinguishes Harvey's research is inductions founded on experimental observation of the action of living tissues.

The service of Vesalius and Harvey in opening the path to biological advance is very conspicuous, but they were not the only pioneers; their work was a part of the general revival of science in which Galileo, Descartes, and others had their part. While the birth of the experimental method was not due to the exertions of Harvey alone, nevertheless it should stand to his credit that he established that method in biological lines. Aristotle and Galen both had employed experiments in their researches, and Harvey's step was in the nature of a revival of the method of the old Greeks.

Harvey's Education.—Harvey was fitted both by native talent and by his training for the part which he played in the intellectual awakening. He was born at Folkestone, on the south coast of England, in 1578, the son of a prosperous yeoman. The Harvey family was well esteemed, and the father of William was at one time the mayor of Folkestone. Young Harvey, after five years in the King's school at Canterbury, went to Cambridge, and in 1593, at the age of sixteen, entered Caius College. He had already shown a fondness for observations upon the organization of animals, but it is unlikely that he was able to cultivate this at the university. There his studies consisted mainly of Latin and Greek, with some training in debate and elementary instruction in the science of physics.

At Padua.—In 1597, at the age of nineteen, he was graduated with the Arts degree, and the following year he turned his steps toward Italy in search of the best medical instruction that could be found at that time in all the world. He selected the great university of Padua as his place of sojourn, being attracted thither by the fame of some of its medical teachers. He was particularly fortunate in receiving his instruction in anatomy and physiology from Fabricius, one of the most learned and highly honored teachers in Italy. The fame of this master of medicine, who, from his birthplace, is usually given the full name of Fabricius ab Aquapendente, had spread to the intellectual centers of the world, where his work as anatomist and surgeon was especially recognized. A fast friendship sprang up between the young medical student and this ripe anatomist, the influence of which must have been very great in shaping the future work of Harvey.

Fabricius was already sixty-one years of age, and when Harvey came to Padua was perfecting his knowledge upon the valves of the veins. The young student was taken fully into his confidence, and here was laid that first familiarity with the circulatory system, the knowledge of which Harvey was destined so much to advance and amplify. But it was the stimulus of his master's friendship, rather than what he taught about the circulation, that was of assistance to Harvey. For the views of Fabricius in reference to the circulation were those of Galen; and his conception of the use of the valves of the veins was entirely wrong. A portrait of this great teacher of Harvey is shown in Fig. 9.

At Padua young Harvey attracted notice as a student of originality and force, and seems to have been a favorite with the student body as well as with his teachers. His position in the university may be inferred from the fact that he belonged to one of the aristocratic-student organizations, and, further, that he was designated a "councilor" for England. The practice of having student councilors was then in vogue in Padua; the students comprising the council met for deliberations, and very largely managed the university by their votes upon instructors and university measures.

It is a favorable comment upon the professional education of his time that, after graduating at the University of Cambridge, he studied four or more years (Willis says five years) in scientific and medical lines to reach the degree of Doctor of Physic.

On leaving Padua, in 1602, he returned to England and took the examinations for the degree of M.D. from Cambridge, inasmuch as the medical degree from an English university advanced his prospects of receiving a position at home. He opened practice, was married in 1604, and the same year began to give public lectures on anatomy.

Fig. 9.—Fabricius, 1537-1619, Harvey's Teacher.

His Personal Qualities.—Harvey had marked individuality, and seems to have produced a powerful impression upon those with whom he came in contact as one possessing unusual intellectual powers and independence of character. He inspired confidence in people, and it is significant that, in reference to the circulation of the blood, he won to his way of thinking his associates in the medical profession. This is important testimony as to his personal force, since his ideas were opposed to the belief of the time, and since also away from home they were vigorously assailed.

Although described as choleric and hasty, he had also winning qualities, so that he retained warm friendships throughout his life, and was at all times held in high respect. It must be said also that in his replies to his critics, he showed great moderation.

Fig. 10.—William Harvey, 1578-1667.

The contemplative face of Harvey is shown in Fig. 10. This is taken from his picture in the National Portrait Gallery in London, and is usually regarded as the second-best portrait of Harvey, since the one painted by Jansen, now in possession of the Royal College of Physicians, is believed to be the best one extant. The picture reproduced here shows a countenance of composed intellectual strength, with a suggestion, in the forehead and outline of the face, of some of the portraits of Shakespeare.

An idea of his personal appearance may be had from the description of Aubrey, who says: "Harvey was not tall, but of the lowest stature; round faced, with a complexion like the wainscot; his eyes small, round, very black, and full of spirit; his hair black as a raven, but quite white twenty years before he died; rapid in his utterance, choleric, given to gesture," etc.

He was less impetuous than Vesalius, who had published his work at twenty-eight; Harvey had demonstrated his ideas of the circulation in public anatomies and lectures for twelve years before publishing them, and when his great classic on the Movement of the Heart and Blood first appeared in 1628, he was already fifty years of age. This is a good example for young investigators of to-day who, in order to secure priority of announcement, so frequently rush into print with imperfect observations as preliminary communications.

Harvey's Writings.—Harvey's publications were all great; in embryology, as in physiology, he produced a memorable treatise. But his publications do not fully represent his activity as an investigator; it is known that through the fortunes of war, while connected with the sovereign Charles I as court physician, he lost manuscripts and drawings upon the comparative anatomy and development of insects and other animals. His position in embryology will be dealt with in the chapter on the Development of Animals, and he will come up for consideration again in the chapter on the Rise of Physiology. Here we are concerned chiefly with his general influence on the development of biology.

His Great Classic on Movement of the Heart and Blood.—Since his book on the circulation of the blood is regarded as one of the greatest monuments along the highroad of biology, it is time to make mention of it in particular. Although relatively small, it has a long title out of proportion to its size: Exercitatio Anatomica de Motu Cordis et Sanguinis in Animalibus, which maybe freely translated, "An Anatomical Disquisition on the Movement of the Heart and Blood in Animals." The book is usually spoken of under the shorter title, De Motu Cordis et Sanguinis. The full title seems somewhat repellent, but the contents of the book will prove to be interesting to general readers. It is a clear, logical demonstration of the subject, proceeding with directness from one point to another until the culminating force of the argument grows complete and convincing.

The book in its first edition was a quarto volume of seventy-eight pages, published in Frankfort in 1628. An interesting facsimile reprint of this work, translated into English, was privately reproduced in 1894 by Dr. Moreton and published in Canterbury. As stated above, it is known that Harvey had presented and demonstrated his views in his lectures since 1616. In his book he showed for the first time ever in print, that all the blood in the body moves in a circuit, and that the beating of the heart supplies the propelling force. Both ideas were new, and in order to appreciate in what sense they were original with Harvey, we must inquire into the views of his forerunners.

Question as to Harvey's Originality.—The question of how near some of his predecessors came to anticipating his demonstration of the circulation has been much debated. It has been often maintained that Servetus and Realdus Columbus held the conception of the circulation for which Harvey has become so celebrated. Of the various accounts of the views of Harvey's predecessors, those of Willis, Huxley, and Michael Foster are among the most judicial; that of Foster, indeed, inasmuch as it contains ample quotations from the original sources, is the most nearly complete and satisfactory. The discussion is too long to enter into fully here, but a brief outline is necessary to understand what he accomplished, and to put his discovery in the proper light.

To say that he first discovered—or, more properly, demonstrated—the circulation of the blood carries the impression that he knew of the existence of capillaries connecting the arteries and the veins, and had ocular proof of the circulation through these connecting vessels. But he did not actually see the blood moving from veins to arteries, and he knew not of the capillaries. He understood clearly from his observations and experiments that all the blood passes from veins to arteries and moves in "a kind of circle"; still, he thought that it filters through the tissues in getting from one kind of vessel to the other. It was reserved for Malpighi, in 1661, and Leeuwenhoek, in 1669, to see, with the aid of lenses, the movement of the blood through the capillaries in the transparent parts of animal tissues. (See under Leeuwenhoek, p. 84.)

The demonstration by Harvey of the movement of the blood in a circuit was a matter of cogent reasoning, based on experiments with ligatures, on the exposure of the heart in animals and the analysis of its movements. It has been commonly maintained (as by Whewell) that he deduced the circulation from observations of the valves in the veins, but this is not at all the case. The central point of Harvey's reasoning is that the quantity of blood which leaves the left cavity of the heart in a given space of time makes necessary its return to the heart, since in a half-hour (or less) the heart, by successive pulsations, throws into the great artery more than the total quantity of blood in the body. Huxley points out that this is the first time that quantitative determinations were introduced into physiology.

Views of His Predecessors on the Movement of the Blood.—Galen's view of the movement of the blood was not completely replaced until the establishment of Harvey's view. The Greek anatomist thought that there was an ebb and flow of blood within both veins and arteries throughout the system. The left side of the heart was supposed to contain blood vitalized by a mixture of animal spirits within the lungs. The veins were thought to contain crude blood. He supposed, further, that there was a communication between the right and the left side of the heart through very minute pores in the septum, and that some blood from the right side passed through the pores into the left side and there became charged with animal spirits. It should also be pointed out that Galen believed in the transference of some blood through the lungs from the right to the left side of the heart, and in this foreshadowed the views which were later developed by Servetus and Realdus Columbus.

Fig. 11.—Scheme of the Portal Circulation According to Vesalius, 1543.

Vesalius, in the first edition of his work (1543) expressed doubts upon the existence of pores in the partition-wall of the heart through which blood could pass; and in the second edition (1555) of the Fabrica he became more skeptical. In taking this position he attacked a fundamental part of the belief of Galen. The careful structural studies of Vesalius must have led him very near to an understanding of the connection between arteries and veins. Fig. 11 shows one of his sketches of the arrangement of arteries and veins. He saw that the minute terminals of arteries and veins came very close together in the tissues of the body, but he did not grasp the meaning of the observation, because his physiology was still that of Galen; Vesalius continued to believe that the arteries contained blood mixed with spirits, and the veins crude blood, and his idea of the movement was that of an ebb and flow. In reference to the anatomy of the blood-vessels, he goes so far as to say of the portal vein and the vena cava in the liver that "the extreme ramifications of these veins inosculate with each other, and in many places appear to unite and be continuous." All who followed him had the advantage of his drawings showing the parallel arrangement of arteries and veins, and their close approach to each other in their minute terminal twigs, but no one before Harvey fully grasped the idea of the movement of the blood in a complete circuit.

Servetus, in his work on the Restoration of Christianity (Restitutio Christianismi, 1553), the work for which Calvin accomplished his burning at the stake, expressed more clearly than Galen had done the idea of a circuit of blood through the lungs. According to his view, some of the blood took this course, while he still admits that a part may exude through the wall of the ventricle from the right to the left side. This, however, was embodied in a theological treatise, and had little direct influence in bringing about an altered view of the circulation. Nevertheless, there is some reason to think that it may have been the original source of the ideas of the anatomist Columbus, as the studies into the character of that observer by Michael Foster seem to indicate.

Realdus Columbus, professor of anatomy at Rome, expressed a conception almost identical with that of Servetus, and as this was in an important work on anatomy, published in 1559, and well known to the medical men of the period, it lay in the direct line of anatomical thought and had greater influence. Foster suggests that the devious methods of Columbus, and his unblushing theft of intellectual property from other sources, give ground for the suspicion that he had appropriated this idea from Servetus without acknowledgment. Although Calvin supposed that the complete edition of a thousand copies of the work of Servetus had been burned with its author in 1553, a few copies escaped, and possibly one of these had been examined by Columbus. This assumption is strengthened by the circumstance that Columbus gives no record of observations, but almost exactly repeats the words of Servetus.

Cæsalpinus, the botanist and medical man, expressed in 1571 and 1593 similar ideas of the movement of the blood (probably as a matter of argument, since there is no record of either observations or experiments by him). He also laid hold of a still more important conception, viz., that some of the blood passes from the left side of the heart through the arteries of the body, and returns to the right side of the heart by the veins. But a fair consideration of the claims of these men as forerunners of Harvey requires quotations from their works and a critical examination of the evidence thus adduced. This has been excellently done by Michael Foster in his Lectures on the History of Physiology. Further considerations of this aspect of the question would lie beyond the purposes of this book.

At most, before Harvey, the circuit through the lungs had been vaguely defined by Galen, Servetus, Columbus, and Cæsalpinus, and the latter had supposed some blood to pass from the heart by the arteries and to return to it by the veins; but no one had arrived at an idea of a complete circulation of all the blood through the system, and no one had grasped the consequences involved in such a conception. Harvey's idea of the movement of the heart (De Motu Cordis) was new; his notion of the circulation (et Sanguinis) was new; and his method of demonstrating these was new.

Harvey's Argument.—The gist of Harvey's arguments is indicated in the following propositions quoted with slight modifications from Hall's Physiology: (I) The heart passively dilates and actively contracts; (II) the auricles contract before the ventricles do; (III) the contraction of the auricles forces the blood into the ventricles; (IV) the arteries have no "pulsific power," i.e., they dilate passively, since the pulsation of the arteries is nothing else than the impulse of the blood within them; (V) the heart is the organ of propulsion of the blood; (VI) in passing from the right ventricle to the left auricle the blood transudes through the parenchyma of the lungs; (VII) the quantity and rate of passage of the blood peripherally from the heart makes it a physical necessity that most of the blood return to the heart; (VIII) the blood does return to the heart by way of the veins. It will be noticed that the proposition VII is the important one; in it is involved the idea of applying measurement to a physiological process.

Harvey's Influence.—Harvey was a versatile student. He was a comparative anatomist as well as a physiologist and embryologist; he had investigated the anatomy of about sixty animals and the embryology of insects as well as of vertebrates, and his general influence in promoting biological work was extensive.

His work on the movement of the blood was more than a record of a series of careful investigations; it was a landmark in progress. When we reflect on the part played in the body by the blood, we readily see that a correct idea of how it carries nourishment to the tissues, and how it brings away from them the products of disintegrated protoplasm is of prime importance in physiology. It is the point from which spring all other ideas of the action of tissues, and until this was known the fine analysis of vital processes could not be made. The true idea of respiration, of the secretion by glands, the chemical changes in the tissues, in fact, of all the general activities of the body, hinge upon this conception. It was these consequences of his demonstration, rather than the fact that the blood moves in a circuit, which made it so important. This discovery created modern physiology, and as that branch of inquiry is one of the parts of general biology, the bearing of Harvey's discovery upon biological thought can be readily surmised.

Those who wish to examine Harvey's views at first hand, without the burden of translating them from the Latin, will find an edition of his complete works translated into English by Willis, and published by the Ray Society, of London.

As is always the case with new truths, there was hostility to accepting his views. In England this hostility was slight on account of his great personal influence, but on the Continent there was many a sharp criticism passed upon his work. His views were so illuminating that they were certain of triumph, and even in his lifetime were generally accepted. Thus the new conception of vital activities, together with his method of inquiry, became permanent parts of biological science.

[CHAPTER IV]

THE INTRODUCTION OF THE MICROSCOPE AND THE PROGRESS OF INDEPENDENT OBSERVATION

The introduction of the microscope greatly increased the ocular powers of observers, and, in the seventeenth century, led to many new departures. By its use the observations were carried from the plane of gross anatomy to that of minute structure; the anatomy of small forms of life, like insects, began to be studied, and also the smaller microscopic animalcula were for the first time made known.

Putting aside the disputed questions as to the time of the invention and the identity of the inventor of the microscope—whether to Fontana, Galileo, or the Jenssens belongs the credit—we know that it was improved by the Hollander Drebbel in the early years of the seventeenth century, but was not seriously applied to anatomical studies till after the middle of that century.

The Pioneer Microscopists

The names especially associated with early microscopic observations are those of Hooke and Grew in England, Malpighi in Italy, and Swammerdam and Leeuwenhoek, both in Holland. Their microscopes were imperfect, and were of two kinds: simple lenses, and lenses in combination, forming what we now know as the compound microscope. Some forms of these early microscopes will be described and illustrated later. Although thus early introduced, microscopic observation did not produce its great results until the nineteenth century, just after magnifying-lenses had been greatly improved.

Fig. 12.—Hooke's Microscope, 1665.
From Carpenter's The Microscope and Its Revelations. Permission of P. Blakiston's Sons & Co.

Robert Hooke (1635-1703), of London, published in 1665 a book of observations with the microscope entitled Micrographia, which was embellished with eighty-three plates of figures. Hooke was a man of fine mental endowment, who had received a good scientific training at the University of Cambridge, but who lacked fixedness of purpose in the employment of his talents. He did good work in mathematics, made many models for experimenting with flying machines, and claimed to have discovered gravitation before Newton, and also the use of a spring for regulating watches before Huygens, etc. He gave his attention to microscopic study for a time and then dropped it; yet, although we can not accord to him a prominent place in the history of biology, he must receive mention as a pioneer worker with the microscope. His book gave a powerful stimulus to microscopy in England, and, partly through its influence, labor in this field was carried on more systematically by his fellow-countryman Nehemiah Grew.

The form of the microscope used by Hooke is known through a picture and a description which he gives of it in his Micrographia. Fig. 12 is a copy of the illustration. His was a compound microscope consisting of a combination of lenses attached to a tube, one set near the eye of the observer and the other near the object to be examined. When we come to describe the microscopes of Leeuwenhoek, with which so much good work was accomplished, we shall see that they stand in marked contrast, on account of their simplicity, to the somewhat elaborate instrument of Hooke.

Grew (1628-1711) devoted long and continuous labor to microscopic observation, and, although he was less versatile and brilliant than Hooke, his patient investigations give him just claim to a higher place in the history of natural science. Grew applied the microscope especially to the structure of plants, and his books entitled Idea of a Philosophical History of Plants (1673) and Anatomy of Vegetables (1682) helped to lay the foundations of vegetable histology. When we come to consider the work of Malpighi, we shall see that he also produced a work upon the microscopic structure of plants which, although not more exact and painstaking than Grew's, showed deeper comprehension. He is the co-founder with Grew of the science of the microscopic anatomy of plants.

It is not necessary to dwell long upon the work of either Hooke or Grew, since that of Malpighi, Swammerdam, and Leeuwenhoek was more far-reaching in its influence. The publications of these three men were so important, both in reference to microscopic study and to the progress of independent investigation, that it will be necessary to deal with them in more detail. In the work of these men we come upon the first fruits of the application of the methods introduced by Vesalius and Harvey. Of this triumvirate, one—Malpighi—was an Italian, and the other two were Hollanders. Their great service to intellectual progress consisted chiefly in this—that, following upon the foundations of Vesalius and Harvey, "they broke away from the thraldom of mere book-learning, and relying alone upon their own eyes and their own judgment, won for man that which had been quite lost—the blessings of independent and unbiased observation."

It is natural that, working when they did, and independently as they did, their work overlapped in many ways. Malpighi is noteworthy for many discoveries in anatomical science, for his monograph on the anatomy of the silkworm, for observations of the minute structure of plants, and of the development of the chick in the hen's egg. Swammerdam did excellent and accurate work upon the anatomy and metamorphosis of insects, and the internal structure of mollusks, frogs, and other animals. Leeuwenhoek is distinguished for much general microscopic work; he discovered various microscopic animalcula; he established, by direct observation, the fact of a connection between arteries and veins, and examined microscopically minerals, plants, and animals. To him, more than to the others, the general title of "microscopist" might be applied.

Since these men are so important in the growth of biology, let us, by taking them individually, look a little more closely into their lives and labors.

Marcello Malpighi, 1628-1694

Personal Qualities.—There are several portraits of Malpighi extant. These, together with the account of his personal appearance given by Atti, one of his biographers, enable us to tell what manner of man he was. The portrait shown in Fig. 13 is a copy of the one painted by Tabor and presented by Malpighi to the Royal Society of London, in whose rooms it may still be seen. This shows him in the full attractiveness of his early manhood, with the earnest, intellectual look of a man of high ideals and scholarly tastes, sweet-tempered, and endowed with the insight that belongs to a sympathetic nature. Some of his portraits taken later are less attractive, and the lines and wrinkles that show in his face give evidence of imperfect health. According to Atti, he was of medium stature, with a brown skin, a delicate complexion, a serious countenance, and a melancholy look.

Accounts of his life show that he was modest, quiet, and of a pacific disposition, notwithstanding the fact that he lived in an atmosphere of acrimonious criticism, of jealousy and controversy. A family dispute in reference to the boundary-lines between his father's property and the adjoining land of the Sbaraglia family gave rise to a feud, in which representatives of the latter family followed him all his life with efforts to injure both his scientific reputation and his good name. Under all this he suffered acutely, and his removal from Bologna to Messina was partly to escape the harshness of his critics. Some of his best qualities showed under these persecutions; he was dignified under abuse and considerate in his reply. In reference to the attacks upon his scientific standing, there were published after his death replies to his critics that were written while he was smarting under their injustice and severity, but these replies are free from bitterness and are written in a spirit of great moderation. The following picture, taken from Ray's correspondence, shows the fine control of his spirit. Under the date of April, 1684, Dr. Tancred Robinson writes: "Just as I left Bononia I had a lamentable spectacle of Malpighi's house all in flames, occasioned by the negligence of his old wife. All his pictures, furniture, books, and manuscripts were burnt. I saw him in the very heat of the calamity, and methought I never beheld so much Christian patience and philosophy in any man before; for he comforted his wife and condoled nothing but the loss of his papers."

Fig. 13.—Malpighi, 1628-1694.

Education.—Malpighi was born at Crevalcuore, near Bologna, in 1628. His parents were landed peasants, or farmers, enjoying an independence in financial matters. As their resources permitted it, they designed to give Marcellus, their eldest child, the advantage of masters and schools. He began a life of study; and, before long, he showed a taste for belles-lettres and for philosophy, which he studied under Natali.

Through the death of both parents, in 1649, Malpighi found himself orphaned at the age of twenty-one, and as he was the eldest of eight children, the management of domestic affairs devolved upon him. He had as yet made no choice of a profession; but, through the advice of Natali, he resolved, in 1651, to study medicine. This advice followed, in 1653, at the age of twenty-five, he received from the University of Bologna the degree of Doctor of Medicine.

University Positions.—In the course of a few years he married the sister of Massari, one of his teachers in anatomy, and became a candidate for a chair in the University of Bologna. This he did not immediately receive, but, about 1656, he was appointed to a post in the university, and began his career as a teacher and investigator. He must have shown aptitude for this work, for he was soon called to the University of Pisa, where, fortunately for his development, he became associated with Borelli, who, as an older man, assisted him in many ways. They united in some work, and together they discovered the spiral character of the heart muscles. But the climate of Pisa did not agree with him, and after three years he returned, in 1659, to teach in the University of Bologna, and applied himself assiduously to anatomy.

Here his fame was in the ascendant, notwithstanding the machinations of his enemies and detractors, led by Sbaraglia. He was soon (1662) called to Messina to follow the famous Castelli. After a residence there of four years he again returned to Bologna, and as he was now thirty-eight years of age, he thought it time to retire to his villa near the city in order to devote himself more fully to anatomical studies, but he continued his lectures in the university, and also his practice of medicine.

Honors at Home and Abroad.—Malpighi's talents were appreciated even at home. The University of Bologna honored him in 1686 with a Latin eulogium; the city erected a monument to his memory; and after his death, in the city of Rome, his body was brought to Bologna and interred with great pomp and ceremony. At the three hundredth anniversary of his death, in 1894, a festival was held in Bologna, his monument was unveiled, and a book of addresses by eminent anatomists was published in his honor.

During his lifetime he received recognition also from abroad, but that is less remarkable. In 1668 he was elected an honorary member of the Royal Society of London. He was very sensible of this honor; he kept in communication with the society; he presented them with his portrait, and deposited in their archives the original drawings illustrating the anatomy of the silkworm and the development of the chick.

In 1691 he was taken to Rome by the newly elected pope, Innocent XII, as his personal physician, but under these new conditions he was not destined to live many years. He died there, in 1694, of apoplexy. His wife, of whom it appears that he was very fond, had died a short time previously. Among his posthumous works is a sort of personal psychology written down to the year 1691, in which he shows the growth of his mind, and the way in which he came to take up the different subjects of investigation.

In reference to his discoveries and the position he occupies in the history of natural science, it should be observed that he was an "original as well as a very profound observer." While the ideas of anatomy were still vague, "he applied himself with ardor and sagacity to the study of the fine structure of the different parts of the body," and he extended his investigations to the structure of plants and of different animals, and also to their development. Entering, as he did, a new and unexplored territory, naturally he made many discoveries, but no man of mean talents could have done his work.

Activity in Research.—During forty years of his life he was always busy with research. Many of his discoveries had practical bearing on the advance of anatomy and physiology as related to medicine. In 1661 he demonstrated the structure of the lungs. Previously these organs had been regarded as a sort of homogeneous parenchyma. He showed the presence of air-cells, and had a tolerably correct idea of how the air and the blood are brought together in the lungs, the two never actually in contact, but always separated by a membrane. These discoveries were first made on the frog, and applied by analogy to the interpretation of the lungs of the human body. He was a comparative anatomist, and the first to insist on analogies of structure between organs throughout the animal kingdom, and to make extensive practical use of the idea that discoveries on simpler animals can be utilized in interpreting the similar structures in the higher ones.

It is very interesting to note that in connection with this work he actually observed the passage of blood through the capillaries of the transparent lungs of the frog, and also in the mesentery. Although this antedates the similar observations of Leeuwenhoek (1669), nevertheless the work of Leeuwenhoek was much more complete, and he is usually recognized in physiology as the discoverer of the capillary connection between arteries and veins. At this same period Malpighi also observed the blood corpuscles.

Soon after he demonstrated the mucous layer, or pigmentary layer of the skin, intermediate between the true and the scarf skin. He had separated this layer by boiling and maceration, and described it as a reticulated membrane. Even its existence was for a long time controverted, but it remains in modern anatomy under the title of the Malpighian layer.

His observation of glands was extensive, and while it must be confessed that many of his conclusions in reference to glandular structure were erroneous, he left his name connected with the Malpighian corpuscles of the kidney and of the spleen. He was also the first to indicate the nature of the papillæ on the tongue. The foregoing is a respectable list of discoveries, but much more stands to his credit. Those which follow have a bearing on comparative anatomy, zoölogy, and botany.

Monograph on the Structure and Metamorphosis of the Silkworm.—Malpighi's work on the structure of the silkworm takes rank among the most famous monographs on the anatomy of a single animal. Much skill was required to give to the world this picture of minute structure. The marvels of organic architecture were being made known in the human body and the higher animals, but "no insect—hardly, indeed, any animal—had then been carefully described, and all the methods of the work had to be discovered." He labored with such enthusiasm in this new territory as to throw himself into a fever and to set up an inflammation in the eyes. "Nevertheless," says Malpighi, "in performing these researches so many marvels of nature were spread before my eyes that I experienced an internal pleasure that my pen could not describe."

He showed that the method of breathing was neither by lungs nor by gills, but through a system of air-tubes, communicating with the exterior through buttonhole shaped openings, and, internally, by an infinitude of branches reaching to the minutest parts of the body. Malpighi showed an instinct for comparison; instead of confining his researches to the species in hand, he extended his observations to other insects, and has given sketches of the breathing-tubes, held open by their spiral thread, taken from several species.

The nervous system he found to be a central white cord with swellings in each ring of the body, from which nerves are given off to all organs and tissues. The cord, which is, of course, the central nervous system, he found located mainly on the ventral surface of the body, but extending by a sort of collar of nervous matter around the œsophagus, and on the dorsal surface appearing as a more complex mass, or brain, from which nerves are given off to the eyes and other sense organs of the head. As illustrations from this monograph we have, in Fig. 14, reduced sketches of the drawings of the nervous system and the food canal in the adult silkworm. The sketch at the right hand illustrates the central nerve cord with its ganglionic enlargement in each segment, the segments being indicated by the rows of spiracles at the sides. The original drawing is on a much larger scale, and reducing it takes away some of its coarseness. All of his drawings lack the finish and detail of Swammerdam's work.

He showed also the food canal and the tubules connected with the intestine, which retain his name in the insect anatomy of to-day, under the designation of Malpighian tubes. The silk-forming apparatus was also figured and described. These structures are represented, as Malpighi drew them, on the left of Fig. 14.

Fig. 14.—From Malpighi's Anatomy of the Silkworm, 1669.

This monograph, which was originally published in 1669 by the Royal Society of London, bears the Latin title, Dissertatio Epistolica de Bombyce. It has been several times republished, the best edition being that in French, which dates from Montpellier, in 1878, and which is prefaced by an account of the life and labors of Malpighi.

Anatomy of Plants.—Malpighi's anatomy of plants constitutes one of his best, as well as one of his most extensive works. In the folio edition of his works, 1675-79, the Anatome Plantarum occupies not less than 152 pages and is illustrated by ninety-three plates of figures. It comprises an exposition of the structure of bark, stem, roots, seeds, the process of germination, and includes a treatise on galls, etc., etc.

In this work the microscopic structure of plants is amply illustrated, and he anticipated to a certain degree the ideas on the cellular structure of plants. Burnett says: "His observations appear to have been very accurate, and not only did he maintain the cellular structure of plants, but also declared that it was composed of separate cells, which he designated 'utricles.'" Thus did he foreshadow the cell theory of plants as developed by Schleiden in the nineteenth century. When it came to interpretations, he made several errors. Applying his often-asserted principle of analogies, he concluded that the vessels of plants are organs of respiration and of circulation, from a certain resemblance that they bear to the breathing-tubes of insects. But his observations on structure are good, and if he had accomplished nothing more than this work on plants he would have a place in the history of botany.

Work in Embryology.—Difficult as was his task in insect anatomy and plant histology, a more difficult one remains to be mentioned, viz., his observations of the development of animals. He had pushed his researches into the finer structure of organisms, and now he attempted to answer this question: How does one of these organisms begin its life, and by what series of steps is its body built up? He turned to the chick, as the most available form in which to get an insight into this process, but he could not extend his observations successfully into periods earlier than about the twenty-four-hour stage of development. Two memoirs were written on this subject, both in 1672, which were published by the Royal Society of England under the titles De Formatione Pulli in Ovo and De Ovo Incubato. Of all Malpighi's work, this has received the least attention from reviewers, but it is, for his time, a very remarkable achievement. No one can look over the ten folio plates without being impressed with the extent and accuracy of his observations. His sketches are of interest, not only to students of embryology, but also to educated people, to see how far observations regarding the development of animals had progressed in 1672. Further consideration of his position in embryology will be found in the chapter on the rise of that subject.

Little is known regarding the form of microscope employed by Malpighi. Doubtless, much of his work was done with a simple lens, since he speaks of examining the dried lungs with a microscope of a single lens against the horizontal sun; but he is also known to have observed with an instrument consisting of two lenses.

Malpighi was a naturalist, but of a new type; he began to look below the surface, and essayed a deeper level of analysis in observing and describing the internal and minute structure of animals and plants, and when he took the further step of investigating their development he was anticipating the work of the nineteenth century.

Jan Swammerdam (1637-1680)

Swammerdam was a different type of man—nervous, incisive, very intense, stubborn, and self-willed. Much of his character shows in the portrait by Rembrandt represented in Fig. 15. Although its authenticity has been questioned, it is the only known portrait of Swammerdam.

Early Interest in Natural History.—He was born in 1637, nine years after Malpighi. His father, an apothecary of Amsterdam, had a taste for collecting, which was shared by many of his fellow-townsmen. The Dutch people of this time sent their ships into all parts of the world, and this vast commerce, together with their extensive colonial possessions, fostered the formation of private museums. The elder Swammerdam had the finest and most celebrated collection in all Amsterdam. This was stored, not only with treasures, showing the civilization of remote countries, but also with specimens of natural history, for which he had a decided liking. Thus "from the earliest dawn of his understanding the young Swammerdam was surrounded by zoölogical specimens, and from the joint influence, doubtless, of hereditary taste and early association, he became passionately devoted to the study of natural history."

Studies Medicine.—His father intended him for the church, but he had no taste for theology, though he became a fanatic in religious matters toward the close of his life; at this period, however, he could brook no restraint in word or action. He consented to study medicine, but for some reason he was twenty-six years old before entering the University of Leyden. This delay was very likely owing to his precarious health, but, in the mean time, he had not been idle; he had devoted himself to observation and study with great ardor, and had already become an expert in minute dissection. When he went to the University of Leyden, therefore, he at once took high rank in anatomy. Anything demanding fine manipulation and dexterity was directly in his line. He continued his studies in Paris, and about 1667 took his degree of Doctor of Medicine.

Fig. 15.—Swammerdam, 1637-1680.

During this period of medical study he made some rather important observations in human anatomy, and introduced the method of injection that was afterward claimed by Ruysch. In 1664 he discovered the valves of lymphatic vessels by the use of slender glass tubes, and, three years later, first used a waxy material for injecting blood-vessels.

It should be noted, in passing, that Swammerdam was the first to observe and describe the blood corpuscles. As early as 1658 he described them in the blood of the frog, but not till fifty-seven years after his death were his observations published by Boerhaave, and, therefore, he does not get the credit of this discovery. Publication alone, not first observation, establishes priority, but there is conclusive evidence that he observed the blood corpuscles before either Malpighi or Leeuwenhoek had published his findings.

Love of Minute Anatomy.—After graduating in medicine he did not practice, but followed his strong inclination to devote himself to minute anatomy. This led to differences with his father, who insisted on his going into practice, but the self-willed stubbornness and firmness of the son now showed themselves. It was to gratify no love of ease that Swammerdam thus held out against his father, but to be able to follow an irresistible leading toward minute anatomy. At last his father planned to stop supplies, in order to force him into the desired channel, but Swammerdam made efforts, without success, to sell his own personal collection and preserve his independence. His father died, leaving him sufficient property to live on, and brought the controversy to a close soon after the son had consented to yield to his wishes.

Boerhaave, his fellow-countryman, gathered Swammerdam's complete writings after his death and published them in 1737 under the title Biblia Naturæ. With them is included a life of Swammerdam, in which a graphic account is given of his phenomenal industry, his intense application, his methods and instruments. Most of the following passages are selected from that work.

Intensity as a Worker.—He was a very intemperate worker, and in finishing his treatise on bees (1673) he broke himself down.

"It was an undertaking too great for the strongest constitution to be continually employed by day in making observations and almost as constantly engaged by night in recording them by drawings and suitable explanations. This being summer work, his daily labors began at six in the morning, when the sun afforded him light enough to enable him to survey such minute objects; and from that time till twelve he continued without interruption, all the while exposed in the open air to the scorching heat of the sun, bareheaded, for fear of interrupting the light, and his head in a manner dissolving into sweat under the irresistible ardors of that powerful luminary. And if he desisted at noon, it was only because the strength of his eyes was too much weakened by the extraordinary efflux of light and the use of microscopes to continue any longer upon such small objects.

"This fatigue our author submitted to for a whole month together, without any interruption, merely to examine, describe, and represent the intestines of bees, besides many months more bestowed upon the other parts; during which time he spent whole days in making observations, as long as there was sufficient light to make any, and whole nights in registering his observations, till at last he brought his treatise on bees to the wished-for perfection."

Method of Work.—"For dissecting very minute objects, he had a brass table made on purpose by that ingenious artist, Samuel Musschenbroek. To this table were fastened two brass arms, movable at pleasure to any part of it, and the upper portion of these arms was likewise so contrived as to be susceptible of a very slow vertical motion, by which means the operator could readily alter their height as he saw most convenient to his purpose. The office of one of these arms was to hold the little corpuscles, and that of the other to apply the microscope. His microscopes were of various sizes and curvatures, his microscopical glasses being of various diameters and focuses, and, from the least to the greatest, the best that could be procured, in regard to the exactness of the workmanship and the transparency of the substance.

"But the constructing of very fine scissors, and giving them an extreme sharpness, seems to have been his chief secret. These he made use of to cut very minute objects, because they dissected them equably, whereas knives and lancets, let them be ever so fine and sharp, are apt to disorder delicate substances. His knives, lancets, and styles were so fine that he could not see to sharpen them without the assistance of the microscope; but with them he could dissect the intestines of bees with the same accuracy and distinctness that others do those of large animals.

"He was particularly dexterous in the management of small tubes of glass no thicker than a bristle, drawn to a very fine point at one end, but thicker at the other."

These were used for inflating hollow structures, and also for making fine injections. He dissolved the fat of insects in turpentine and carried on dissections under water.

An unbiased examination of his work will show that it is of a higher quality than Malpighi's in regard to critical observation and richness of detail. He also worked with minuter objects and displayed a greater skill.

The Religious Devotee.—The last part of his life was dimmed by fanaticism. He read the works of Antoinette Bourignon and fell under her influence; he began to subdue his warm and stubborn temper, and to give himself up to religious contemplation. She taught him to regard scientific research as worldly, and, following her advice, he gave up his passionate fondness for studying the works of the Creator, to devote himself to the love and adoration of that same Being. Always extreme and intense in everything he undertook, he likewise overdid this, and yielded himself to a sort of fanatical worship until the end of his life, in 1680. Had he possessed a more vigorous constitution he would have been greater as a man. He lived, in all, but forty-three years; the last six or seven years were unproductive because of his mental distractions, and before that, much of his time had been lost through sickness.

The Biblia Naturæ.—It is time to ask, What, with all his talents and prodigious application, did he leave to science? This is best answered by an examination of the Biblia Naturæ, under which title all his work was collected. His treatise on Bees and Mayflies and a few other articles were published during his lifetime, but a large part of his observations remained entirely unknown until they were published in this book fifty-seven years after his death. In the folio edition it embraces 410 pages of text and fifty-three plates, replete with figures of original observations. It "contains about a dozen life-histories of insects worked out in more or less detail. Of these, the mayfly is the most famous; that on the honey-bee the most elaborate." The greater amount of his work was in structural entomology. It is known that he had a collection of about three thousand different species of insects, which for that period was a very large one. There is, however, a considerable amount of work on other animals; the fine anatomy of the snail, the structure of the clam, the squid; observations on the structure and development of the frog; observations on the contraction of the muscles, etc., etc.

It is to be remembered that Swammerdam was extremely exact in all that he did. His descriptions are models of accuracy and completeness.

Fig. 16 shows reduced sketches of his illustrations of the structure of the snail. The upper sketch shows the central nervous system and the nerve trunks connected therewith, and the lower figure shows the shell and the principal muscles. This is an exceptionally good piece of anatomization for that time, and is a fair sample of the fidelity with which he worked out details in the structure of small animals. Besides showing this, these figures also serve the purpose of pointing out that Swammerdam's fine anatomical work was by no means confined to insects. His determinations on the structure of the young frog were equally noteworthy.

Fig. 16.—From Swammerdam's Biblia Naturæ.

But we should have at least one illustration of his handling of insect anatomy to compare more directly with that of Malpighi, already given. Fig. 17 is a reduced sketch of the anatomy of the larva of an ephemerus, showing, besides other structures, the central nervous system in its natural position. When compared with the drawings of Malpighi, we see there is a more masterly hand at the task, and a more critical spirit back of the hand. The nervous system is very well done, and the greater detail in other features shows a disposition to go into the subject more deeply than Malpighi.

Besides working on the structure and life-histories of animals, Swammerdam showed, experimentally, the irritability of nerves and the response of muscles after their removal from the body. He not only illustrates this quite fully, but seems to have had a pretty good appreciation of the nature of the problem of the physiologist. He says:

"It is evident from the foregoing observations that a great number of things concur in the contraction of the muscles, and that one should be thoroughly acquainted with that wonderful machine, our body, and the elements with which we are surrounded, to describe exactly one single muscle and explain its action. On this occasion it would be necessary for us to consider the atmosphere, the nature of our food, the blood, the brain, marrow, and nerves, that most subtle matter which instantaneously flows to the fibers, and many other things, before we could expect to attain a sight of the perfect and certain truth."

In reference to the formation of animals within the egg, Swammerdam was, as Malpighi, a believer in the pre-formation theory. The basis for his position on this question will be set forth in the chapter on the Rise of Embryology.

Fig. 17.—Anatomy of an Insect: Dissected and Drawn by Swammerdam.

There was another question in his time upon which philosophers and scientific men were divided, which was in reference to the origin of living organisms: Does lifeless matter, sometimes, when submitted to heat and moisture, spring into life? Did the rats of Egypt come, as the ancients believed, from the mud of the Nile, and do frogs and toads have a similar origin? Do insects spring from the dew on plants? etc., etc. The famous Redi performed his noteworthy experiments when Swammerdam was twenty-eight years old, but opinion was divided upon the question as to the possible spontaneous origin of life, especially among the smaller animals. Upon this question Swammerdam took a positive stand; he ranged himself on the side of the more scientific naturalists against the spontaneous formation of life.

Antony van Leeuwenhoek (1632-1723)

In Leeuwenhoek we find a composed and better-balanced man. Blessed with a vigorous constitution, he lived ninety-one years, and worked to the end of his life. He was born in 1632, four years after Malpighi, and five before Swammerdam; they were, then, strictly speaking, contemporaries. He stands in contrast with the other men in being self-taught; he did not have the advantage of a university training, and apparently never had a master in scientific study. This lack of systematic training shows in the desultory character of his extensive observations. Impelled by the same gift of genius that drove his confrères to study nature with such unexampled activity, he too followed the path of an independent and enthusiastic investigator.