SCIENCE FROM AN EASY CHAIR

BY THE SAME AUTHOR

• Extinct Animals
• The Kingdom of Man
• From an Easy Chair

A.—“YELLOW” OR IMMATURE EEL: NOT DESCENDING TO THE SEA (FEMALE)

B.—“SILVER” OR MATURE EEL IN BRIDAL DRESS DESCENDING TO THE SEA (FEMALE), A SMALLER INDIVIDUAL THAN “A”

HEAD OF IMMATURE AND MATURE SPECIMENS OF THE COMMON EEL OF THE NATURAL SIZE.

ORIGINAL WATER-COLOUR DRAWINGS FROM LIVE SPECIMENS

[Transcriber’s Note: The original images are around 5¾ inches (14.5cm) wide and 1½ inches (4cm) high.]

SCIENCE FROM AN
EASY CHAIR

BY
Sir RAY LANKESTER
K.C.B., F.R.S.

WITH EIGHTY-FOUR ILLUSTRATIONS

SECOND EDITION

METHUEN & CO. LTD.
36 ESSEX STREET W.C.
LONDON

[PREFACE]

This volume is a collection of some of the papers which I have contributed to the Daily Telegraph during the years 1908-1909, under the title “Science from an Easy Chair.” I have revised and corrected the letterpress, and have added some illustrations. A smaller volume containing earlier papers was published by Messrs. Constable in 1908, with the title From an Easy Chair. It is my intention now to produce additional volumes (under the title “Easy Chair Series”) as their constituent articles accumulate, and I hope to be able to publish a second and a third instalment at no distant date.

I should like to draw the special attention of the reader to the Frontispiece ([Plate I.]), which is very beautifully executed, and is, I believe, the first coloured drawing yet published showing the difference between the adult “silver” eel and the more abundant immature “yellow” eel—sometimes called the “frogmouthed eel.” The original drawings were prepared for me through the kindness of Dr. Petersen, of Copenhagen, who is the discoverer of many interesting facts about the common eel, and is director of the Danish Biological Laboratory.

I also wish to draw the attention of any one who is kind enough to look at this preface to one or two more of my illustrations, because they are, I think, of exceptional interest, and should be looked at, at once, before a decision not to read the book is made. These are the prehistoric engraving of a horse’s head, with rope-bridle in place, on [page 81]; the drawings of the leaves of the American Poison-vine and of the Virginian Creeper on [page 95]; of the nettle-sting on [page 113]; of the Dragon of the Hesperides on [page 122]; of the big tadpoles on [page 217]; of the jumping bean on [page 298], and its moth on [page 301]; of the ant milking a green-fly for its honey-dew on [page 324]; and lastly, the accurate drawing on [page 370] of the most ancient human skull yet discovered, and the other drawings of skulls (all to the scale of one-third the actual length), and those of prehistoric weapons and carvings which follow it. These drawings have been made from original scientific memoirs, or in some cases from actual specimens, for the present volume.

E. RAY LANKESTER

February 1910

[CONTENTS]

[LIST OF ILLUSTRATIONS]

DIAGRAMS IN THE TEXT

PLATES

SCIENCE FROM AN EASY CHAIR

[I]
SCIENCE AND PRACTICE

The delight which is experienced by those who discover new things in the various branches of science is, no doubt, very great. To reveal to other men processes, properties, existences in the natural world hitherto unsuspected, or, if suspected, yet eluding the grasp of man, is to do something which gives to him who does it a sense that he is of value in the world—a sense which will uphold him and enable him to endure adversity, and even persecution, with equanimity. But there is, perhaps, a greater and more vivid satisfaction for those who do or make great and splendid things which all men can see, and for which all men are grateful. The great artist—poet, painter, builder, or musician—has this satisfaction, and so also has the man who, by a combination of personal energy and clearness of intellectual vision, applies scientific knowledge to the accomplishment of great public works, and to the acquirement of that control by mankind of the natural conditions hostile to human progress which we may call, as did Lord Bacon, “the establishing of the kingdom of man.”

The men who have expelled yellow fever from Cuba and Panama have not merely done a piece of sanitary cleaning up; they have first imagined and then created, by the force of human will, directed and maintained by conviction of the reality of science, a new thing—the tropics without deadly fever, the tropics as a healthy and welcome home for the white man. That is comparable to the work of a great artist in the directness of its appeal; it is in its actual detail the result of the combination of the skill of the engineer with the foresight and absolute domination of his human agents of a military genius.

For this magnificent work the highest credit is due to the United States chief sanitary officer, Colonel Gorgas. It is well known how the American Medical Commission in Cuba proved six years ago that yellow fever is conveyed from man to man solely and entirely by a gnat common in Central America, known as Stegomyia, and further, how by carrying out measures for preventing the entrance of these gnats into dwelling-houses, and especially by keeping them away from yellow fever patients so that they fail to obtain and carry the yellow fever germ, even if they do bite healthy men, Colonel Gorgas and his associates practically eradicated yellow fever in Cuba. The bite of the Stegomyia gnat is the only way in which a man can acquire yellow fever, and the gnat which bites him must have taken up the germs of yellow fever from another man—twelve days (no less) previously.

The application of this knowledge and the methods devised to give it effect is what has now rendered the construction of the Panama Canal by the United States Government possible. The French Canal Company employed an army of labourers, numbering from 15,000 to 18,000 men. They lost, almost entirely by death from yellow fever and malaria, so many of their workmen that others refused to undertake the deadly job, and there was a general panic. The death-rate was in 1884 over 60 per 1000. In 1885 it was over 70 per 1000. The work was abandoned. In May 1904 Colonel Gorgas and his forces took possession of the canal zone. This is a zone of territory running fifty miles north and south, with a good-sized town—Colon—at one end of it and another—Panama—at the other end of it. Many hundreds of men were at once organised and set to work to destroy in both the towns the Stegomyia gnat. This was effected by doing away with all the breeding-places of the gnat, that is, screening and covering every water receptacle in the town, so that the gnats or mosquitoes cannot breed. Then a fumigating process was carried out in all houses and buildings, great and small, to destroy such gnats as were still alive. No less than 200,000 lb. of pyrethrum and 400,000 lb. of sulphur were used in this fumigation. In December 1905 the last case of yellow fever occurred. It took sixteen months of the work just described to effect this.

In a different way the Anopheles gnat or mosquito, which carries the germ of malaria from man to man, was got rid of. This gnat breeds in clean water, where grass and weeds grow; it belongs chiefly to country districts. As it rarely flies more than 200 yards it was sufficient to destroy the breeding pools within that distance of the workmen’s houses, camps, and villages. All the windows and doors of all houses were fitted with wire-gauze screens, which prevent the entrance of the gnats, and the population was furnished with quinin, a dose of 3 grs. a day being ordered to bring the men into such condition that the malaria parasite would not thrive in the blood even if introduced.

The object with which Colonel Gorgas and his associates started was accomplished in less than two years. The control of yellow fever and malaria has become even more complete in the two years which have followed. It is two years since yellow fever disappeared from the entire zone, including the two towns. Malaria has not been so completely destroyed. The employés of the Canal Commission and Panama Railway now number 45,000. The death-rate of this entire force, including both black (33,000) and white (12,000) employés, was, in the month of December 1907 only 18 per 1000 per annum—less than that of the city of Liverpool, which was 20, or that of Salford, which was over 19. Of all the white employés the death-rate was only 13 per 1000 per annum. In the year 1906 (whole year), among the 6000 white employés who had come from the United States, including some 1200 women and children, their families, the death-rate from disease was only 4 per 1000. Pneumonia has been a chief cause of death among the negro labourers, but seldom affects the whites. Malaria caused, in the whole army of labourers, only six deaths in December 1907, as against thirteen in the smaller army at work in the same month in 1906. There were 800 cases of malaria in the whole army of 45,000 employés in December 1907.

It is thus apparent that Colonel Gorgas has converted this deadly zone from which negroes and white men hurried in a panic of fear twenty years ago into a region as healthy—that is to say, with as low a death-rate—as an ordinary North American or English city. No doubt allowance must be made in the comparison for the special nature of the population brought together on the canal zone. This is favourable to a low death-rate, in so far as it consists of strong adults, excluding old people and very young children, but unfavourable in so far as it consists of negroes and mean whites, who are even less amenable to sanitary regulations and precautions than the population of an English city. Colonel Gorgas writes that now that it is shown that any population coming into the tropics can protect itself against yellow fever and malaria by measures which are both simple and inexpensive, the Anglo-Saxon will find life in the tropics more healthful than in the temperate zones, and tropical countries which offer a much greater return for man’s labour than do those of the chilly temperate zone, will be in the course of the next two or three centuries occupied and populated by the white races. Such an unpleasantly cold spring as that which all Europe endured last year makes one wish that the tropics generally were already arranged by Colonel Gorgas for our reception, and provided with a sanitated white-faced population. We could go and live there, warm and comfortable, all the year round, enjoying the rich luxuriance of tropical nature without fear of either chill or fever.

[II]
UNIVERSITY TRAINING

At Manchester last year, when they installed Lord Morley, the Secretary of State for India, as Chancellor of the University, the Right Hon. Arthur Balfour delivered a very interesting address, in which he declared himself a believer in the gospel of “Science the Master.” Mr. Balfour’s speech did not imply any disregard for the pursuit of historical knowledge and a training in literature and the use of language, but it was a clear recognition of the fact that when the great purpose for which universities exist is considered it must be asserted in no hesitating terms that the discovery of new knowledge is the most important activity which a university can foster. To train men (and women, too) to use their faculties not merely to acquire knowledge of what has been discovered by others in the past, but to discover new things and to gain further control over the conditions in which we live, and to secure further understanding not only of nature but of man—that is the great business of the university.

It was fortunate that Mr. Balfour was present and able to strike this note, for Lord Morley, the new Chancellor, had not expressed any such conception of the aims of a university. He declared that, so long as the Greeks have anything to teach us we should not cease to study the Greeks. But, whilst we may agree to this, it is well to remember that, though pleasure can still be obtained from Greek poetry and prose by those who have thoroughly mastered the Greek language, yet almost all, if not quite all, that the Greeks have to teach us has been by this time translated and dealt with by our own writers. Consequently, although we may cordially approve of the study of ancient civilisations and ancient literatures and languages, both Greek and barbarian, as part of the enterprise of a university, it is somewhat excessive, not to say belated, to set up the study of Greek or of any other historic language and civilisation as the chief and distinctive boon which universities can offer to their scholars. The matter has, indeed, been thrashed out, and Greek, together with what is called the “study of literature” (but is usually an ineffective dabbling in it), has been put into its proper subordinate place in all the universities of Europe and in most of those of Great Britain. The illusion that flowers of speech and mastery of phrase (though all very well if honestly used) are an indication of any knowledge or capacity which can be of service to the community, has been, in late years, to a very large extent, dispelled.

The concluding words of Mr. Balfour’s speech were: “The great advancement of mankind is to be looked for in our ever-increasing knowledge of the secrets of nature—secrets, however, which are not to be unlocked by the men who pursue them for purely material ends, but secrets which are open in their fulness only to men who pursue them in a disinterested spirit. The motive power which is really going to change the external surface of civilisation, which is going to add to the well-being of mankind, which is going to stimulate the imagination of all those who are interested in the universe in which our lot is cast—that lies after all with science. I would rather be known as having added to the sum of our knowledge of the truth of nature than anything else I can imagine. Unfortunately for me, my opportunities have lain in different directions.”

That is a splendid confession of faith. I do not remember that any German statesman of like authority and standing has ever given expression to so full and ample a belief in the value of science. Yet German statesmen have acted, though they have not spoken. They have arranged for, and continually are arranging for, a far larger expenditure of public money upon scientific training and investigation than is assigned to such purposes in this country. Every department of government in Germany has its thoroughly trained, well-taught, well-paid body of scientific experts and investigators, and, moreover, the whole official world, from the Emperor downwards, has a real understanding of what science is, of the folly of attempting to proceed without it, or allowing persons who are ignorant of it to act as administrators. The need for science is not merely recognised in words, but steps are taken, and have been taken now for many years, actually to secure in German public offices and public administration the predominance of that scientific knowledge which the German statesmen, as well as Mr. Balfour, consider so necessary. Is it too much to hope that in this country those who recognise the value and importance of scientific knowledge will also take steps to re-arrange our Government departments so as to give them the advantage of guidance by men trained in the knowledge of nature, rather than by men ignorant of the very existence of such knowledge?

The universities hold the central position in this matter, and it is their influence and wealth which the State should insist on directing towards the extension and diffusion of science. Those who address the public on this subject not infrequently take what seems to me to be a disastrous line at the start. They speak of the new universities as the universities of the people, and hand over Oxford and Cambridge, with their enormous endowments, their history and tradition, to the wealthy class. Such usurpation cannot be tolerated. It is monstrous that the endowments of the colleges of Oxford and Cambridge, which were thoroughly popular and democratic in their foundation, should be, even for a moment, regarded as the peculiar property of the wealthy. It is also monstrous to suppose that it is anything less than disastrous to consign the well-to-do classes in any community to an empty sham of ancient “culture” rather than to imbue them with the real and inspiring culture of the modern renaissance. It is because this notion is allowed to gain ground that the enormous funds of the colleges and universities of Oxford and Cambridge, amounting to more than three-quarters of a million pounds annually, are to a large extent, though not exclusively, employed in keeping up a couple of huge boarding-schools, which are shut for six months in the year.

It is owing to this that it is the rarest thing to find in Oxford or in Cambridge a great teacher who lectures or demonstrates to an eager following of disciples. An overwhelming majority of the young men who go as students to these universities have no intention of studying anything. They are sent there in order to be submitted to college discipline and to have, subject to that safeguard, a good time. A large number are handsomely paid by scholarships in order to induce them to go there—and would not go there at all unless they were so paid. They do not find such teachers there and such an effective occupation of their student years as would induce them, if unpaid, to seek the university, or to pay fees out of their own pockets for the opportunities of seriously pursuing any branch of learning or science within its walls.

The inefficiency of the old universities is to a large extent the cause of the neglect and ignorance of science in the well-to-do class, who furnish the men who become Government officials of all kinds and members of professions which influence public opinion. But this inefficiency of the old universities is not due to their devotion to literary studies and to abstract science, nor to their objection to the pursuit of practical and commercial studies. That excuse is sometimes put forward for them, though at this moment they are, in fact, setting up laboratories and lecture-rooms for engineering, agriculture, forestry, mining, and such applications of science. Nor is it money which is really wanting at either Oxford or Cambridge, although they are both begging for it from the public. What Oxford and Cambridge want is not money but men; men as teachers—“professors” is the usual title given to them in a university—who must be the ablest, each in his own line, in the whole world. If such professors existed in either Oxford or Cambridge, and were allowed to teach, the town (if not the colleges!) would be full to overflowing of students—eager to pay their fees and to spend, not three short terms of seven weeks in each year, but the whole year, and many years, in the laboratories and lecture-rooms of those commanding men.

To obtain such men—to set the machinery at work—you must pay them handsomely, and give them authority and the means of work. Once they were at work, the mere fees of the students would furnish a splendid revenue. There is plenty of money at Oxford and at Cambridge—a superabundance, in fact—which could and should be applied to this purpose, namely, that of securing and establishing there the greatest teachers in the world. The money is at present administered by the colleges according to the directions given in recent Acts of Parliament, and by no means in any blind obedience to the original intentions of the founders of the colleges. It is to a large extent wasted. That portion of it paid out as “scholarships” is for the most part wasted in bringing students to a place where they cannot get the best opportunities of study, and the rest is unwisely applied (not so much by the tenants for life or administrators of college funds as by rigid Act of Parliament) to providing an excessive number of totally inadequate salaries by which a corresponding number of young men are induced to enter upon the career of teachers as underpaid college Fellows.

[III]
DARWIN’S THEORY

On Wednesday, the 1st of July 1908, half a century had passed since Darwin’s Theory of the Origin of Species was made known to the world. Fifty years have now been completed since that immortal book, The Origin of Species, was published, and a hundred years since Charles Darwin was born.

It is not every one who is in a position to understand how great and momentous was the occasion when Sir Charles Lyell and Dr. Joseph Hooker communicated to the Linnean Society of London, on the 1st of July 1858, two papers, one by Charles Darwin, the other by Alfred Russel Wallace, under the common title, “On the Tendency of Species to form Varieties: and on the Perpetuation of Varieties and Species by Natural means of Selection.” The reason for this conjoint communication to the Linnean Society was that Darwin, who had been working for years at the subject, and had already, in 1842, drawn up a statement of his theory, not for publication, but for the consideration and criticism of his friend Hooker—unexpectedly received from Alfred Russel Wallace, who was, and had been for some years, away in the Malay Archipelago—a manuscript of an essay on the origin of species, containing views identical with his own, and even phrases similar to those he had himself found it necessary to invent. Thus Wallace speaks of the “struggle for existence,” whilst Darwin had used the term “struggle for life.” Darwin had been urged by his friends before this to publish an abstract or statement of his conclusions, but now that he had received Wallace’s manuscript, he declared in a letter to Hooker, “I would far rather burn my whole book than that he or any other man should think that I had behaved in a paltry spirit.” And so Lyell and Hooker took the matter in hand, and communicated to the Linnean Society, accompanied by an explanatory statement, the two independent papers, setting forth, as they say, “the results of the investigations of the indefatigable naturalists, Mr. Charles Darwin and Mr. Alfred Wallace.” Such loyalty and regard to each other as Darwin and Wallace showed then and ever after form a delightful feature in the history of this great discovery. A wonderful thing is that Hooker, now Sir Joseph Hooker, the greatest botanist of the past century, the constant friend and comrade of Darwin, is still alive, and that Alfred Russel Wallace, too, is still with us. They both were present when the Linnean Society celebrated the meeting of fifty years ago.

The views of Darwin and Wallace have now become the established doctrine of science. They have led to the universal recognition of “the origin of species by descent with modification.” That is a statement, in other words, to the effect that all the various kinds of living things have been gradually produced by natural birth from predecessors which differ from them only slightly in the later stages of time, but become simpler and less like their descendants as we go further back, until we reach the simplest living things. It has led to the conviction that there has been no exceptional or “miraculous” suspension of the order of Nature in this process, but that all has come about in due and regular course, in virtue of the properties of natural things, which we know as the laws of physics and chemistry. Most important and dominating of all these results is the inevitable one that man himself has come from animal ancestors, in the same way, and—(this is the greatest and most far-reaching conclusion of all)—that he is still subject to those natural processes of change and development by which he has reached his present phase; that he must completely understand them and control them (so far as such control is possible) in order to maintain a healthy, happy, and improving race of men on the face of the globe. This great possession—the earth and all that lives on it—is, as Lord Bacon phrased it three hundred years ago—the Kingdom of Man. Man has but to use his intelligence in order to take control of it. The knowledge of his own relation to it, and of the ways in which the human race is affected for good and for ill, through the operation of the self-same processes which affect the breeding, the improvement, the health, the disease, the destruction, and the perfecting of other living things, has once and for all been placed within man’s reach by the discoveries of Darwin and Wallace.

Before Darwin—that is, before 1st July 1858—the origin of the different species of animals and plants was called by great thinkers like Sir John Herschel, the astronomer, “the mystery of mysteries.” The word “species” was defined as “an animal or plant which in a state of nature is distinguished by certain peculiarities of form, size, colour, or other circumstance from any other animal or plant, and propagates after its kind individuals perfectly resembling the parent, its peculiarities being therefore permanent.” So wrote a great naturalist in the days before Darwin. This definition may be illustrated by two common English birds—the rook and the crow. They differ from each other in slight peculiarities of form, structure, and habits, and, moreover, rooks always produce rooks, and crows always produce crows, and they do not interbreed. Therefore it was held that all the rooks in the world had descended from a single pair of rooks, and all the crows in like manner from a single pair of crows, while it was considered impossible that crows could have descended from rooks, or rooks from crows. The “origin” of the first pair of each kind was a mystery, and by many persons was held to have been due to a miraculous and sudden act of “creation.” But besides our crow and rook, there are about thirty other birds in various parts of the world so much like our crow and rook that they are commonly called crows, and are all regarded as “species” of the genus crow (or Corvus). It was held before Darwin that all the individuals of each of these “species” were descended from an ancestral pair of crows of that species. There would have been thirty different original kinds, the “origin” of which was unknown, and by naturalists was regarded as a mystery. Now, on the contrary, it is held that all the thirty living species are descended from one, not from thirty, ancestral species, and have been gradually modified to their present character in different parts of the world; and, further, that this ancestral species was itself derived by slow process of change and natural birth from preceding crow-like birds no longer existing.

As Mr. Alfred Russel Wallace has said in his most readable and delightful book, Darwinism—where he gives all the credit and glory to his great fellow-worker: “Darwin wrote for a generation which had not accepted evolution—a generation which poured contempt on those who upheld the derivation of species from species by any natural law of descent. He did his work so well that ‘descent with modification’ is now universally accepted as the order of nature in the organic world, and the rising generation of naturalists can hardly realise the novelty of this idea, or that their fathers considered it a scientific heresy to be condemned rather than seriously discussed.”

For those who are not naturalists or men of science it is an object-lesson of the highest importance, that the speculations and observations which have led to the general acceptance of a new view as to the origin of the species of birds, butterflies, and flowers—in itself apparently a matter of no consequence to human life and progress—should have necessarily led to a new epoch in philosophy, and in the higher state-craft; in fact, to the establishment of the scientific knowledge of life as the one sure guide and determining factor of civilisation. How to breed a healthy, capable race of men, how to preserve such a race, how to educate and to train it, so that its best qualities of mind and body may be brought to activity and perfection—this is what Darwinism can teach us, and will teach us when the great subjects of inheritance and of variation are more fully investigated by the aid of public funds, and when the human mind has been as carefully examined and its laws as well ascertained, as are those of the human body. There is no reason for delay; no excuse for it. For two thousand years the learned men of Europe debated as to whether this or that place was the site of ancient Troy, or whether there ever was such a place at all. At last (only twenty-five years ago) a retired man of business, named Schliemann, had a “happy thought”—it was not the thought of a learned pedant, but of a scientific investigator. He said, “Let us go and see.” And at the expense of a few thousand pounds he went and found Troy and Mycenæ, and revealed—“dis-covered”—the whole matter. That was the most tremendous and picturesque triumph of the scientific method over mere talk and pretended historical learning which has ever been seen since human record has existed. It ought to be told to every boy and girl, for it is the greatest and most obvious proof of the overwhelming power of the investigation of tangible things and the futility of chatter, which has ever been seen. It is enough to inspire hope and belief in experiment even in the breast of a Member of Parliament, or of a Minister of the Crown.

[IV]
DARWIN’S DISCOVERIES

A large proportion of the public are not aware of the amount of experiment and observation carried out by the great naturalist whose memory was honoured by a splendid ceremony at the University of Cambridge in the summer of 1909. There are, I am sure, not a few who are under the impression that Darwin, sitting in his study or walking round his garden, had “a happy thought,” namely, that man is only a modified and improved monkey, and proceeded to write an argumentative essay, setting forth the conclusion that mankind are the descendants of some remote ancestral apes. Of course there is an increasing number of more careful and inquiring men and women who take advantage of the small price at which Mr. Darwin’s wonderful book, The Origin of Species, is now to be bought, and have read that and some of his other writings, and accordingly know how far he was from being the hasty and fanciful theorist they previously imagined him to be. It is the great distinction of Darwin that he spent more than twenty years of his life in accumulating the records of an enormous series of facts and observations tending to show that the species or “kinds” of animals and plants in nature can and do change slowly, and that there is, owing to the fact that every pair produces a great number of offspring (sometimes many thousand), of which only a single pair, on the average, survive, a necessary selection of those which are to survive and breed, accompanied by a rejection and destruction of the rest. This “natural selection” or survival of favoured varieties, he was able to show, must operate like the selection made by breeders, fanciers, and horticulturists, and has in all probability (for in a history extending over hundreds of thousands of years we must necessarily deal with “probabilities,” and not with direct demonstration) produced new forms, new kinds, better adapted to their surroundings than the parental forms from which they are derived.

It was necessary, in order that Darwin should persuade other naturalists that his views were correct, that he should show by putting examples “on the table” that variations occur naturally and in great diversity; further, that there is great pressure in the conditions of life, and a consequent survival of the best-suited varieties; further, that there is in reproduction a transmission of the peculiar favouring character or quality which enables a variety to survive, and thus a tendency to perpetuate the new quality. It was not enough for Darwin to “imagine” that these things might be so, or to make the notion that they are so plausible by arguments drawn from existing knowledge. He had to do that: but also he had to make new inquiries and discover new things about animals and plants which fitted in with his theory and would not fit in either with the notion that all plants and animals were created—as the poet Milton supposed—out of lumps of earth and muddy water, suddenly, in the likeness of their present-day descendants, nor with some other notions, such as that of the able and gifted French naturalist Lamarck. And he spent the later twenty years of his life in doing so, just as he had spent the previous twenty years in collecting a first series of facts and observations justifying his theory before he announced it to the world.

A great difference between Lamarck and Darwin exists, not only in their two theories as to the mode of origin of the vast diversified series of kinds or species of plants and animals, but in their way of stating and dealing with the theory which each thought out and gave to the world. Lamarck had a great knowledge of the species of plants and animals, partly through having collected specimens himself when he was an officer in the French Republican army which was employed on the Mediterranean shores of France and Italy more than a hundred years ago, and partly through his later official position in the great natural history museum at Paris, where large collections passed through his hands. He was a man of very keen insight and excellent method, and did more to plan out a natural and satisfactory “classification” of animals than any one between his own day and that of Linnæus. His theory of the origin of species was essentially an opposition to the then popular view that the species of living things have been made by the Creator so as to fit the conditions in which they live. Lamarck contradicted this view, and said in so many words that the real fact is that the peculiar specific characters of animals or of plants have not been created for their conditions, but, on the contrary, that the conditions in which they live have created the peculiarities of living things. In so far his conception was the same as Darwin’s. But Lamarck then said to himself: How do the conditions create the peculiarities of different living things? And he answered this question by an ingenious guess, which he published to the world in a book called Philosophical Zoology, without taking any steps to test the truth of his guess.

That is where Lamarck’s method and attitude as a scientific man is so greatly inferior to that of Darwin. Lamarck, sitting in his study, said animals (and plants too) must be affected by the conditions around them, so that an individual as it lives and grows becomes to a certain degree slightly changed by and adapted to those conditions. This, he said, we all see in human beings and familiar animals and plants. Now, he said, we have only to admit that the changes so acquired are (especially when both parents have been similarly changed) transmitted to the young in the process of generation, and to some degree “intensified,” in order to recognise that of necessity there is in nature a constant change and progression of living forms, consisting in a more and more elaborate “adaptation” to the conditions of life, which will be varied and lead to new adaptations as the living things spread over the earth or as geological changes occur. He cited the long neck of the giraffe as an example of what he meant. In regions where there was frequent and extensive drought, a deer-like creature would eat the lower leaves of trees when the grass was dried up and dead. It would strain and stretch its neck in reaching after the higher leaves, and the individuals thus straining and stretching would become an inch or two longer in the neck in consequence. These individuals would, said Lamarck, transmit their increased length of neck to their offspring, who again would strain and stretch after higher leaves, and get a further increase of neck-length, and so it would go on, little by little, over many thousand generations, until the neck-stretchers had become well marked and distinguished by their long necks from such of their ancestral stock as survived in other regions where, the grass being good, there was no inducement to straining and stretching the neck.

Now the great difference between Lamarck and Darwin is that Lamarck was quite content to state the ingenious supposition illustrated by the imaginary history of the giraffe, and to declare that this was the law of Nature and is actually going on every day, without, so to speak, getting out of his chair. He never attempted to show by observation or experiment that such a change of form as the stretching of the neck by straining after food could and did occur, or that if it did that it could be transmitted by a parent or couple of parents to their offspring. And consequently for many years no one attached much value to Lamarck’s notions on the subject. When, fifty years later, Darwin’s very different theory became widely received, based on the demonstrable fact that congenital variations (not stretchings and warpings acquired in the lifetime of a parent, but variations which are inborn, and occur in some but not other individuals living under one and the same set of conditions) are transmitted to offspring, and that those among these variations which are favourable to success in life will enable their possessor to survive and to produce young inheriting those favourable variations—then it occurred to those naturalists who were inclined to believe in Lamarck’s suggestion to inquire into the solid facts in regard to that also, and to see whether his bare statement was true. From that day to this, it has never been shown that it is true. It is, indeed, to begin with, a rare thing to find instances of either wild animals or wild plants which, growing up in unusual conditions, have their structure altered and “adapted” so as to be more serviceable in those unusual conditions than their usual structure would be; and in those cases where such adaptive alterations have been produced, every experimenter is agreed in stating that he has found that when (even after several generations in the changed conditions) the young are restored to their original conditions, they simply grow up into the original forms: no permanent change in the stock or race has been effected. Every attempt to show by experiment that a new character can be acquired by the stock in this way, and show itself by heredity alone—when the modifying adapting conditions are removed—has completely failed.

On the other hand, Darwin himself and his followers have made almost endless experiments and observations on plants and animals, establishing facts as to structure and the relation of special kinds of living things to their surroundings which can only be explained on the supposition that Darwin’s theory is true in detail; that is to say, not merely that the kinds of animals and plants have arisen from previous kinds by natural descent—that supposition is much older than either Darwin or Lamarck—but that the method by which the transformation has been brought about is (a) the occurrence in every generation of every animal and plant of minute variations in every, or nearly every, part, and (b) the continual selection in the severe struggle for existence of those individuals to grow to maturity and reproduce, which happen to present favourable variations, which variations are accordingly transmitted to the next generation, and may be intensified, so far as intensification is of value, in each succeeding generation.

A book full of observations and reflections about the structure, habits, and mode of occurrence and geography of a great number of plants and animals is Darwin’s Journal of Researches, published in 1845, and now republished as A Naturalist’s Voyage. In order to know very minutely the differences and resemblances between all the kinds or species of one group of living things Darwin studied for eight years the “cirrhipedes,” the name given to the sea-acorns and ships’ barnacles which occur in all parts of the world, some living on rocks, some on the backs of turtles, others on whales, on the feet of birds, on bits of floating wood or of pumice-stone, and some on one another! They are all hermaphrodites, but Darwin found in several a most singular thing, namely, the existence of minute males, complemental to and parasitic on the hermaphrodites. His discovery was doubted and denied, but he had the pleasure of seeing it at last fully confirmed thirty years after his book on cirrhipedes was published.

Darwin discovered that the presence of the same species of plants and of some few animals on distant mountain summits and in the Arctic region is due to the former extension of ice between these situations during the last glacial period. He was, before everything else and by necessity for the examination of his theory, a geologist, and wrote many valuable geological memoirs. The history of the origin of the species of living things consists largely in tracing them to extinct creatures, and in showing what were the possible migrations and what the conditions of land and water, temperature and vegetation, in past periods, and in regard to given areas of the globe. The book on the Fertilisation of Orchids was the first published by Darwin after the Origin of Species. In it he showed how the marvellous shapes and colours and mechanisms of the flowers of orchids are adapted to ensure cross-fertilisation by insects, and how they can be explained as originating by the natural selection of variations—if the value of cross-fertilisation is once recognised. The explanation of the reason for the existence of two kinds of primrose flowers—the short-styled and the long-styled—clearly arrived at by him as being a mechanism to secure cross-fertilisation, delighted him in 1862, and led him to discover the same sort of modification in other flowers. Then, in 1864, he published his researches on Climbing Plants, and later a book on the Movements of Plants, in which he discovered the mechanism and the wonderful variety of movements of plants, and showed their value to the plant, and consequent origin, by natural selection.

He especially loved to discover evidence that plants can do many things which had been thought to be only within the powers of the other section of living things—the animals; and finding during one summer holiday that the beautiful little sun-dew moves its red-knobbed tentacles so as to entrap minute insects, he discovered the whole history of Insectivorous Plants, and showed that there are many plants of various groups which catch insects and digest them in a sort of stomach, as an animal might do. Thus the water-holding pitchers of the pitcher-plants of tropical forests were explained as being food-catchers and digesters of great value to the nutrition of the plant, and their gradual formation by variation and natural selection rendered comprehensible.

His greatest book next to the Origin—containing an immense quantity of original notes and observations and valuable information from all kinds of breeders and fanciers—is the Variation of Animals and Plants under Domestication (1868). The facts recorded are discussed in the light of the great theory, and honest, fair-minded consideration is given to those which present difficulties as well as to those which clearly favour it. In 1871 came the Descent of Man, followed in 1872 by the Expression of the Emotions in Men and Animals—in which, again, it was shown that the facts as to the likeness between man and apes can be explained on the theory that natural selection and survival of favourable variations have been at work, and that the facts are hopelessly without meaning or explanation on any other hypothesis. His last published book was on The Formation of Vegetable Mould through the Action of Worms, in which he not only showed what an important part earthworms play in burying stones and rocks, and in fitting the ground for the growth of plants, but recorded some discoveries as to the senses of worms and as to their treatment of leaves by a digestive fluid exuded from the mouth so as to soften a leaf before swallowing it.

Every one of Darwin’s books abounds with new facts and new points of view disclosed by the application to first one thing and then another of his vivifying discovery-causing theory of natural selection. The subsidiary theory of the selection of brilliantly coloured males by females in pairing, as a cause of the brilliant colours and patterns of many birds and insects, is developed in his Descent of Man. It led him to many important discoveries and observations as to the colouring and ornamentation of animals, and when considered, together with Wallace’s and Bates’s theory of mimicry and of the warning and protective colourings of insects, goes far to explain all the specific colouring of animals and plants as due to natural selection and survival. A theory which has produced such prodigious results in the way of “explaining” all forms, colours, habits, and occurrences of living things—as has that of Charles Darwin—simply holds the field against all comers. When Lamarck’s theory has been shown to be consistent with the most elementary facts as to heredity, and further to afford a rational explanation of any group of biological facts, it will be time to consider how far it may be entertained in conjunction with Darwin’s theory—but not until then.

[V]
DARWIN’S THEORY UNSHAKEN

It seems ill-mannered, if not ill-natured, that the year of the centenary of Charles Darwin’s birth should have been chosen by owners of anonymous pens in order to alarm the public mind with the preposterous statement that his celebrated and universally accepted theory of the origin of the species or kinds of plants and animals by natural selection, or “the survival of favoured races in the struggle for life,” is undermined and discredited. Such a statement once coolly made in the public Press is necessarily believed by a large number of uninformed readers, and, like all calumny, is none the less relished by the foolish, and, for the moment, none the less harmful, because it is baseless.

Those who seek to belittle Darwin’s theory show, whenever they venture to enter into particulars, that they do not know what Darwin’s theory is. They confuse it with other theories, and even imagine that some enthusiastic Darwinians who have tried to add a chapter here or there to Darwin’s doctrine, are opponents of the great theory. Let me briefly state what that theory is:

It rests on three groups of facts—matters of observation, which are not theory or guess work at all—but admitted by every one and demonstrated every day. These are—(1) Living things, each in its kind, produce a far larger number of young than can possibly grow up to maturity, since the kind of food and the situation necessary to each kind are limited and already occupied. Only one oyster embryo out of every five million produced (the reader may refer to [p. 137] on this subject) grows up through all the successive stages of youth to the adult state. The total number of a species of animal or plant on the whole area where it is found does not increase. Even in those which produce a small number of young, there is great destruction, and taking all the individuals into consideration, only a single pair of young arrive at maturity to replace their parents. There is no exception to the rule that every organic being naturally multiplies at so high a rate that, if not destroyed, the progeny of a single pair would soon cover the earth. The elephant is reckoned the slowest breeder of known animals; it commences to breed at 30 years of age, dies at 100, and has six young in the interval. After 750 years, supposing all the offspring of a single pair fulfilled the rule and were not destroyed in an untimely way, there would be nearly nineteen million elephants alive descended from the first pair. There is then no doubt as to the enormous excess in the production of young living things, nor as to their necessary competition with one another of the most severe and inexorable kind; nor again as to the necessary death, in many species, of hundreds and thousands, for every one which survives to maturity and in its turn breeds.

(2) The second great fact is that among all the young born to a pair of parents, no two are exactly alike, nor are any exactly like their parents; nor are any two taken from all produced by all parents of that species exactly alike. They all resemble their parents at the corresponding age, in a general way and even very closely; but the resemblance is far from amounting to identity. This is called “variation.” It is familiar to us all in the case of the organism which we know best, and observe most closely, namely, man. It is also a matter of common observation in the case of dogs, cats, horses, and other domesticated animals. Many of these “variations” are exhibited in points of size, proportion, and colour, which are easily noted at once by the eye. But “variation” is really a deep-seated thing, and depends on causes which lie below the surface. We know that the offspring of men and of animals and of plants, give evidence of variations in what we call constitution, tendency, temperament, aptitude, strength, and that the colour, and even size of this or that part, are really only indications of a deep-seated difference in the living chemistry, the forces of nutrition and growth which reside in the living substance. The fact that many thousands of a species may be born and only a few survive, means therefore that many thousand varieties, often varieties not readily measured by the eye, are produced in each generation, from which a few individuals are in some way “selected” for survival.

(3) The third great fact is that though there is variation, amongst all the offspring in each generation, there is also a continual and definite inheritance by offspring of the qualities and structure of their parents to a degree which altogether preponderates over the variations. To put it in another way, we all know that every parental organism transmits to its young not only the qualities and structure of the species, or of the race, or of the family, but also transmits its own peculiarities or variations in which it departed from its parents, and from its brothers and sisters. This is best illustrated by our daily experience of human families.

These facts being admitted, and abundantly illustrated and traced in detail by years of observation and experimental breeding in all kinds of living things by hundreds of careful observers who have published the records of their studies, we come to the step where Darwin makes use of supposition or hypothesis. The question is, “Does the one which, out of the thousands of slightly different varieties, survives—do so by haphazard? or is there a necessarily acting state of things which selects that one special variety for survival?” Gardeners and breeders of pigeons, dogs, and cattle deliberately select the variations which they desire, breed from them, and so carry on by inheritance the special variation—whilst they ruthlessly destroy or restrain from breeding the numerous other variations in their “stock” which they do not desire. “If,” said Darwin, “there is any necessarily selective mechanism in Nature which could act as the breeder does, new varieties might be ‘naturally’ selected, and changes of form and appearance naturally established, which in the course of long ages would amount to such marked differences as separate what we call one species from another.” He showed that there is a natural mechanism of the required kind. “Since,” he says, “the competition among the members of any one kind or species for a place in life is so very severe, and the hostile circumstances so varied, and since all the competing offspring differ by ‘variation’ ever so little from one another, those varieties which are better suited in even the smallest degree to hold their own not merely in fighting with the others, but in withstanding injurious influences, in escaping enemies, and in procuring food, will be the ones which will survive, when a large number of cases, many thousands, extending over a large area and many years, are considered. Those which are ‘best fitted’ to get through the exceedingly numerous dangers and difficulties of life will be the survivors.” Hence we get the survival of the fit—the fit variations—by natural selection in the struggle for life. This, it will be observed, is an inference, and not a direct observation.

So long as the conditions remain practically or effectively unchanged, the animal or plant already “fitted” to them will be succeeded by those of its offspring which most resemble it in the essential points of “fitness.” But we know that in the course of ages, more or less rapidly, climates change, land emerges from the sea, islands join continents, continents become scattered islands, animals and plants migrate into regions previously uninhabited by them. As such changes gradually come on, the natural selection of favoured varieties will necessarily lead to the survival of others than those previously favoured, other variations better suited to the new conditions will survive.

The natural selection of favoured variations would not amount to much, were the variations not perpetuated by transmission to the young which they produce. This, it is common knowledge [see [(3)]], does take place. It is known also that a variation so established is as a result of the regular process of variation presented in larger volume or emphasised in character in some individuals of subsequent generations, and by continued “natural selection” it may become more and more a prominent or dominant feature of the race.

So far, the only assumption made by Mr. Darwin is that any or some of the endless variations which occur in all the offspring of wild plants and animals, in various combinations and degree in each individual, can be sufficiently important to determine the survival or non-survival of the organisms possessing them. That is a matter which has been largely studied and discussed. The verdict of those who have studied on the spot (as Darwin himself did) the teeming life of the tropics, the insects, birds, and plants of those regions, is that we are justified in considering that small variations are sufficiently important to turn the scale in favour of survival or non-survival. It is not easy for a man who is not a determined naturalist, constantly observing the ways of wild living things, to appreciate the evidence as to the efficacy of small variations, even were I able here to submit it to him. It is to be found in the published works of an army of investigators. In any case it is granted that effective variations—whether small or great—occur in nature, and that natural selection favours and perpetuates the new and fitter variety to the exclusion of the less fit.

The real difficulty to most people comes in the supposition next made by Mr. Darwin—namely, that this slow process of change by natural selection of favoured variations and their transmission and perpetuation by inheritance is sufficient to effect by its continued operation through enormous ages of time the conversion of a race of ancestral three-toed zebras into the one-toed horse of to-day; before that, of five-toed beasts into three-toed; at an earlier stage of fishlike creatures into four-footed land animals, and so on. You have to picture the whole series of animals and of plants which are now or ever have been, as two gigantic family trees or pedigrees, meeting in common ancestors of the simplest grade of microscopic life. All the diverging branches and twigs of these great “family trees” have been determined by the adaptation of living form to the endlessly varied conditions of life on this planet, by the natural selection or survival of variations and the transmission and accumulation of those variations from parent to offspring. This is a tremendous demand on the imagination. It is, however, not a difficult one to concede, when one is acquainted with the facts and conclusions of geology. The history of the crust of the earth was explained twenty years before the date of Darwin’s theory by Charles Lyell as due to the continued action through immense periods of time of the same natural forces which are now at work. And, moreover, the examination of the successive stratified deposits of the earth’s crust has yielded the remains of whole series of animals and of plants (simpler in character the older and deeper the rock in which they occur), which can be satisfactorily explained and interpreted as the ancestral forms from which present organisms have been developed.

The theory of the natural selection of variations as the moving spring in the gradual development of living forms from simplest living matter is Darwin’s theory. It is not possible to find any naturalist of consideration who does not accept it. There are various views held and discussed as to the cause of variation, as to the importance of small and of big variations, as to the non-transmissibility of some kinds of variation, and as to various peculiarities in regard to inheritance. They do not for the most part touch the main features of Mr. Darwin’s theory. No doubt we are learning and shall learn more about the facts of variation and the details of the process of hereditary transmission, but such increase of knowledge has not tended to undermine Mr. Darwin’s theory, and does not seem at all likely to do so.

On the occasion of the celebration at Cambridge in 1909 of the centenary of Darwin’s birth, I was invited by the Vice-Chancellor, on behalf of the University, to deliver in the Senate-house an address, others being given by representatives of the United States (Prof. Osborne), of Germany (Prof. Hertwig), and of Russia (Prof. Metchnikoff). The following is the text of that address:—

“I feel it a great honour to be called upon to speak here to-day, and to stand, on behalf of the naturalists of the British Empire, by the side of the distinguished men whose orations you have just heard.

“I think that the one thing about Charles Darwin which the large majority of British naturalists would wish to be to-day proclaimed, in the first place—with no doubtful or qualifying phrase—is that, in their judgment, after these fifty years of examination and testing, his ‘theory of the origin of species by means of natural selection or the preservation of favoured races in the struggle for life’ remains whole and sound and convincing, in spite of every attempt to upset it.

“I am not stating more than the simple truth when I say that, in the judgment of those who are best acquainted with living things in their actual living surroundings, ‘natural selection’ retains the position which Mr. Darwin claimed for it of being the main means of the modification of organic forms.

“Our admiration for the vast series of beautiful observations and interesting inquiries carried out by Darwin during his long life must not lead us to forget that they were devised by him in order to test the truth of his theory and to meet objections to it, and that they were triumphantly successful. They, together with the work of Alfred Russel Wallace and many of their followers, have more and more firmly established Darwin’s theory. On the other hand, no attempt to amend that theory in any essential particular has been successful.

“The nature of organic variation and of the character of the variations upon which natural selection can and does act was not, as we are sometimes asked to believe, neglected or misapprehended by Darwin. The notion that these variations are large and sudden was considered by him, and for reasons set forth by him at considerable length rejected. That notion has in recent years been resuscitated, but its truth has not been rendered probable by evidence either of such an accurate character or of such pertinence as would justify the rejection of Darwin’s fundamental conception of the importance of minute and ubiquitous variations.

“Further, in regard to the important facts of heredity connected with the cross-breeding of cultivated varieties, especially in regard to the blending or non-blending of their characters in their offspring and as to prepotency, it seems to me important that we should now and here call to mind the full and careful consideration given to this subject by Darwin. We cannot doubt that he would have been deeply interested in the numerical and statistical results associated with the name of Mendel. Those results tend to throw light on the mechanisms concerned in hereditary transmission, but it cannot be shown that they are opposed in any way to the truth of Darwin’s great theoretical structure—his doctrine of the origin of species.

“It has often been urged against Darwin that he did not explain the origin of variation, and especially that he has not shown how variations of sufficient moment to be selected for preservation in the struggle for existence have in the first place originated. The brief reply to the first objection is that variation is a common attribute of many natural substances of which living matter is only one. In regard to the second point, I desire to remind this assembly that Darwin described with special emphasis instances of what he calls ‘correlated variability.’ In my opinion he has thus furnished the key to the explanation of what are called useless specific characters and of incipient organs. That key consists in the fact that a general physiological property or character of utility is often selected and perpetuated, which carries with it distinct, even remote, correlated growths and peculiarities obvious to our eyes, yet having no functional value. At a later stage in the history of such a form these correlated growths may acquire value and become the subject of selection.

“It is thus, as it seems to me, and as, I believe, to the great body of my brother naturalists, that Darwin’s theory stands after fifty years of trial and application.

“The greatness of Charles Darwin’s work is, and will be for ever, one of the glories of the University of Cambridge. It is fitting on the present occasion that one who speaks on behalf of English men of science should call to mind the nature of his connection with this great University and the peculiarly English features of his life-story and of that fine character which endears his memory to all of us as much as his genius excites our admiration and reverence. Darwin was not, like so many a distinguished son of Cambridge, a scholar or a fellow of his college, nor a professor of the University. His connection with the University and the influence which it had upon his life belong to a tradition and a system which have survived longer in our old English universities than in those of other lands. Darwin entered the University, not seeking a special course of study with the view of professional training, nor aiming at success in competitive examinations for honours and emolument. He came to Cambridge intending to become a clergyman, but blessed with sufficient means and leisure to enable him to pursue his own devices, to collect beetles, to explore the fen country, and to cultivate his love of nature. It was thus that he became acquainted with that rare spirit Henslow, the Cambridge professor of botany, and it is through Henslow and the influence of his splendid abilities and high personal character upon Darwin that Cambridge acquired the right to claim the author of the ‘Origin of Species’ as a product of her beneficence and activity as a seat of learning.

“As an Oxford man and a member of Exeter College, I may remind this assembly that in precisely the same way Darwin’s dearest friend and elder brother in science, Charles Lyell, had a few years earlier entered at Exeter College, and by happy chance fallen under the influence of the enthusiastic Buckland, the University reader in geology and a Canon of Christ Church. The wise freedom of study permitted and provided for in those long-passed days by Oxford and Cambridge is what has given the right to claim the discovery, if not the making, of Lyell to the one and of Darwin to the other.

“Darwin’s love of living nature and of the country life are especially English characteristics; so, too, I venture to think, are the unflinching determination and simple courage—I may even say the audacity—with which he acquired, after he had left the University, the wide range of detailed knowledge in various branches of science which he found necessary in order to deal with the problem of the origin of the species of plants and animals, the investigation of which became his passion.

“The unselfish generosity and delicacy of feeling which marked Darwin’s relations with a younger naturalist, Alfred Russel Wallace, are known to all. I cannot let this occasion pass without citing those words of his which tell us most clearly what manner of man he was and add to his splendid achievements as an intellectual force—a light and a beauty of which every Englishman must be proud. When in old age he surveyed his life’s work he wrote:—‘I believe that I have acted rightly in steadily following and devoting my life to science.’

“To have desired to act ‘rightly,’ and to be able to think of success in life as measured by the fulfilment of that desire, is the indication and warrant of true greatness of character. We Englishmen have ever loved to recognise this noble kind of devotion in our national heroes.”

[VI]
METCHNIKOFF AND TOLSTOI

The Darwin celebration at Cambridge, in June 1909, brought a wonderful assemblage of celebrated biologists from all parts of the world to this country. There never has been seen such a company of great discoverers of all nationalities in the field of natural history and the science of living things, as were present in the University of Cambridge during that week. Even philosophers, moralists, and jurists were present to join with the one great political leader of our own country who really knows and appreciates the importance of the scientific study of Nature—the Right Hon. Arthur J. Balfour—in his fervent and heartfelt tribute to the influence of Darwin’s work and theory in all departments of human knowledge, thought, and activity. One of the most remarkable men present was Elie Metchnikoff. He represented both Russia, the country of his birth and earlier scientific work, and his adopted country, France, where, as sub-director of the Institut Pasteur, his later and most important researches have been carried on. Russia was also represented by Salensky, late director of the Museum of St. Petersburg, well known to us all as a discoverer in the embryology (growth from the egg) of marine animals, and by Timiriazeff, the botanist, renowned for his work on the mode in which leaf-green or “chlorophyll” enables green plants to obtain their food from the gases of the atmosphere. France had other representatives in Edmond Perrier, director of the Paris Museum, and Prince Roland Bonaparte.

Metchnikoff was one of the four representatives selected by the University to deliver orations in the Senate House in honour of Darwin. He especially drew attention to the influence of Darwin’s theory on the study of disease. The recognition of the derivation of man from animal ancestors, and of the complete community of the structure and the chemical activity of the organs of man with those of the organs of animals, had made (he said) the study of the diseases of animals a necessary feature in the understanding of the diseases of man. The far-reaching principle of Darwin that the mechanisms and processes observed in the bodies of plants and of animals (including man) must have been selected in the struggle for existence and perpetuated, because of their utility, led Metchnikoff to inquire what is the value or use of the process called inflammation and of the “eating corpuscles,” or “phagocytes” (so named by him), which wander from the blood into inflamed tissues. This question had led him to the discovery that the phagocytes engulf and destroy disease-germs, and are the great protectors of the animal and human body against bacteria and other germs which enter cut and wounded surfaces, and would start disease were there not “inflammation,” which is nothing more nor less than a nerve-regulated stagnation of the circulation of the blood at the wounded spot, and the consequent arrival at this spot of thousands of “phagocytes,” which pass out of the stagnant blood through the walls of the fine blood-vessels. These armies of phagocytes proceed to eat up and destroy all the germs which fall on to the wound—from the air, from dirty surfaces, and from the skin. The utility of inflammation and its gradual development, according to Darwinian principles, in the animal series, was shown twenty years ago by Metchnikoff. His important work on “immunity” and on infection and on protection against germ-caused disease is thus seen to be one of the many flourishing and valuable branches of knowledge which have originated from Darwin’s great conception and his example in experiment and inquiry.

Metchnikoff is now devoting all his attention to the possibility of prolonging human life. The facts seem to show that if we ate and drank only what is best for us, and led lives regulated by reason and knowledge, we should, nearly all, attain to 80 or even 100 years of age, having healthy minds and healthy bodies. We should die quietly and comfortably at the end, with much the same feeling of contentment in well-earned final repose as that which we now experience in going to sleep at the end of a long and happy day of healthy exercise and activity. Metchnikoff thinks that the causes of too early death may be ascertained, and when ascertained avoided or removed. In 1870, in a little book on Comparative Longevity, I distinguished what we may call the “possible life,” or “potential longevity,” of any given human being from his or her “expectation” of life. Potential longevity has been well called our “lease” of life. It is probably not very different in different races of men or individuals, and is probably higher than King David thought, being 100 to 120 years, and not merely 70 years. We all, or nearly all, fail to last out our “lease” owing to accidents, violence, and avoidable, as well as unavoidable, disease; so that 70 years is named as our tenure when the injury done to us by unhealthy modes of life and by actual disease are considered as inevitable. Metchnikoff proposes to discover and to avoid those conditions which “wear down” most of us and produce “senility” and “death” before we have really run out our lease of life.

Human beings die most abundantly in the earliest years of life. Statistics show that at birth the chance or expectation of life is only 45 years, whilst at 10 years old you may expect to live to be 61. At 30 you have not a much better chance—you will probably, if you are what is called a “healthy” life, die when you are 65. But if you survive to be 50 you may expect, if you have not any obvious disease or signs of “break up,” another twenty years, and will probably die at 70; surviving to 60, you may expect, if you are what passes for “healthy,” to live to 73. Now, it is especially with regard to life after 40 or 50 years of age that Metchnikoff is interested. Those who have survived the special dangers and difficulties of youth, and have arrived at this mature age, ought to be able to realise much more frequently than they do something like the full “lease of life.” There seems to be no reason why they should not avoid the usual rapid “senile changes” or weakness of old age, and survive, as a few actually do, to something like 100. The causes of “senile change” and the way to defeat their operation are what Metchnikoff is studying. Hardening of the walls of the arteries set up by certain avoidable diseases contracted in earlier life, and by the use of alcohol (not only to the degree which we call “drunkenness,” but to such a degree as to make one depend on it as a “pick-me-up”), is an undoubted cause of that weakness and liability to succumb to other diseases which is so general after 50 years of age. The causes which produce hardened arteries can be avoided. Another cause of senile changes is declared by Metchnikoff, to arise from the continual absorption of poisonous substances produced by the decomposition of partially digested food in the lower bowel or large intestine. This is at present the chief subject of his study. It is to prevent the formation of these poisons that he has introduced the use of sour milk, prepared with the lactic ferment. Since the Cambridge celebration he has been in London in order to examine the condition of certain patients from whom a distinguished English surgeon has found it necessary to remove the “large intestine.” Metchnikoff wishes to ascertain what bacteria, poison-producing or other, are present in these patients, and what is their general chemical condition now that this poison-producing part of the digestive canal has been taken from them.

In Paris, Metchnikoff has some very interesting experiments in progress with bats. He uses the large tropical fruit-eating bats, or “flying foxes.” They have a very short intestine, and very few bacteria and of very few kinds are to be found in its contents. On the other hand, there are as many as thirty distinct kinds of bacteria producing putrefaction or other chemical change in the digestive canal of man—and their quantity is gigantic. They pervade the whole contents of the human digestive canal by millions. By properly feeding the flying foxes in his laboratory in Paris Metchnikoff has actually succeeded in getting rid of all bacteria from their digestive canal, so that he now has adult mammalian animals, not very remote from man in their structure, food, and internal chemistry, which are absolutely free from the intestinal parasitic bacteria which he supposes to cause poisoning and senile changes in man. It is obvious, without pursuing the matter into further detail here, that Metchnikoff is now in a position to test his views as to the action of particular kinds of bacteria—he has animals which are free from them. He can make an experiment, keeping some of his bats still free from bacteria and causing some to be largely infected by this or that kind, and he can compare the result in regard to the health and chemical condition of the animals. So, too, the patients from whom the lower intestine has been removed may very probably furnish him (through his assistant who remains in London) with important facts for comparison with the condition of persons who have not been deprived of this part of the digestive apparatus.

I have given this sketch of what my friend is doing in order to furnish some notion of the kind of investigation which he pursues. He does not expect to extend the “lease” of human life, but by ascertaining in a definite scientific way the true rules of internal and external “hygiene” he does hope to give mankind an increased “expectation” of life; in fact, to enable a vastly larger number of men and women to enjoy that lease to the full, and to die without disappointment and regret, even with contentment and pleasure, at the end of it.

Metchnikoff was in Russia in the spring of 1909, and spent a day with Tolstoi. They were “fêted” and photographed together, the greatest artist and the greatest scientist of Russia. Tolstoi is 81 years of age. He took Metchnikoff out alone for a drive in his pony-cart so as to talk with him without interruption. “What do you think of life?” was the first question he asked, and one which it took my friend some time to answer. In regard to vegetarianism the two great men did not agree. When Metchnikoff declared that there was less cruelty on man’s part in killing wild animals to eat them than in leaving them to die by the tooth and claw of predaceous animals or from starvation, Tolstoi observed that that was argument and reason, and that he paid no attention to them; he only guided himself (he said) by sentiment, which he felt sure told him what was good and right! He was, however, deeply interested in an account of the cannibalism of savage races of men, concerning which he seemed to be quite uninformed. He also was profoundly interested in Metchnikoff’s view that Goethe, in the second part of Faust, is chiefly bent upon depicting the persistence of the amorous passion in old age—of which Goethe himself was an example—and Tolstoi declared that this gave a new meaning to the poem, which he had always hitherto found dull and unintelligible. But when Metchnikoff described in glowing words the joy and even rapture with which man will hereafter welcome the repose and mystery of death, having completed a long and healthy life of some hundred years, Tolstoi declared that this was indeed a fine conception, although it was entirely subversive of his own notions as to the significance of life and death. Tolstoi also stated that he had written his stories rapidly and without effort, but that his essays on morality and religion had cost him great labour; and, further, that he could not now remember the former, though the latter still were developing and incessantly occupied his thought.

It was admitted with regret by Darwin that he ceased in middle age to care for poetry and art, though there seems to be no doubt that he mistook fatigue and preoccupation of mind for a real change in taste and power of appreciation. It is interesting to place beside this the case of the great literary artist, Tolstoi, who not only frankly confesses that he refuses to be guided by reason and follows sentiment, but is also profoundly ignorant upon all the most ordinary topics of human life outside his own village, and of all Nature and her workings. Would Tolstoi have been a greater or a smaller artist if he had had a larger knowledge of the things that are? Was Darwin’s great scientific achievement really related to an innate indifference to what is called “poetry”? I will not now discuss the matter, but I am convinced that so far as natural gift is concerned, the keenest scientific capacity is not only compatible with the fullest sensibility to art and with the power of poetical vision and expression, but is often accompanied by them; and, further, that the work of an artist, if he is a great artist, cannot be hampered by knowledge. It is only the small talent or the feeble genius that can be paralysed rather than developed by the fullest experience and the widest knowledge. Necessary incompatibility of mental qualities has no place in this matter; what has led to the erroneous assumption that it has, is the excessive exercise by exceptional individuals of certain powers—a specialism necessary for effort and success, but deliberately chosen, and not due to an inborn one-sidedness.

[VII]
THE LAND OF AZURE BLUE

The Côte d’Azur whither many of my readers will be travelling—in thought, if not in reality—about Easter time, is well named the Land of Azure Blue, for it is the blueness of the sea, of the sky, and of the distant rocks and mountains, as well as much of the vegetation, which is when the sun shines, its special charm. And although one has some wet and some cloudy days, yet the sun does shine there with a strength and brilliancy not to be enjoyed in the early part of the year on the Atlantic and North Sea coast. This tract of country, more commonly known to English people as the Riviera, has very special meteorological conditions owing to its position as the narrow strip of shore-line existing between the vast mass of the Western Alps and the Mediterranean Sea. It is warmed by the sea, and lies too close under the mountains to be caught by any winds from the north, and at many points is also effectively protected from both east and west winds by rocky spurs of the great mountain chain.

The Riviera is a constant source of delight to those who love flowers and beautiful vegetation of all kinds. But few of its visitors appreciate the fact that it is really from end to end one big garden, cultivated for ages by its inhabitants, and full of plants introduced by man which at present seem at first sight to be characteristic natives of it, but are, in reality, quite distinct from its primitive vegetation. This primitive vegetation is now represented only in what is locally called the “maquis”—what we should, perhaps, term the “scrub” or “bush” in English. It comprises some pines, the juniper, the lovely rock roses, balsams, rosemary, the giant heath (bruyère), from which our briar-root pipes are made, the larger thyme, the myrtle, the rose of Provence, two kinds of lavender, and many aromatic plants with grey hairy leaves, and often provided with sharp thorns as additional defences against browsing goats. The delicious perfumes of these hardy inhabitants of the dry, rocky grounds, where little or no grass can flourish, are developed by them as a protection against browsing animals, who cannot tolerate much of these pungent volatile oils, although mankind extracts them and uses them in the manufacture of such scents as eau-de-Cologne and also in cookery.

Many a visitor to the Riviera never strays from the cultivated fields and roadways into this scrub-land. The olive tree, which forms so prominent and beautiful a feature in the panorama of gardens which unrolls itself as we steam or drive along the coast from Toulon to Mentone and from Mentone to Genoa and Spezzia, is not a native plant; it was introduced in prehistoric times, and has been again and again re-established by emigrants from Italy; but it was brought to Italy from the East. It is astonishing how many of the cultivated trees of the Riviera have the same kind of history—the vine came from India in prehistoric times, the fig tree more recently from Persia, the lemon from India, the orange and the peach tree from China. All of them were introduced in very ancient times to the eastern parts of the Mediterranean basin, and so gradually were carried to the shores of the Ligurian sea, and would die out here were they not to a certain extent under the care of ownership.

The so-called “mimosa,” so abundant here, with its pretty, sweet-scented, yellow blossom, is an Australian acacia, only introduced some sixty years ago; whilst the eucalyptus—a most picturesque and effective addition to the landscape—is a still later introduction from Australia. The cypress, that darkest and most shapely of conifers, long lines of which proclaim to the traveller as he passes Avignon his arrival in the true “South,” is not a native of these parts, although it flourishes in suitable situations. It was introduced in mediæval times from the East. So, too, the palms, though some have been cultivated for centuries, have been largely imported from extra European localities in the last century. There is a native European palm. It is a kind of fan-palm, and grows here. I have gathered it in Sicily. It does not “rear its stately head” more than a foot from the ground, and is known to botanists as Chamærops humilis. The gigantic Mexican agave and the prickly-pear cactus were introduced in the seventeenth century from the New World, though, according to Sir Herbert Tree’s scenery, they were growing at Cape Miseno in the time of Antony and Cleopatra! Bamboos of many kinds have been introduced here from the Far East, and flourish exceedingly.

The orange tree was brought from India (whither it was carried from China) and established in Southern Europe in mediæval times, though known to the ancient Greeks and Romans. There are as many as 120 different varieties of the orange tree now cultivated on the shores of the Mediterranean, including, besides those which are valued for their sweet juicy pulp, those which furnish bergamot oil and similar aromatic products. The “issue pea” of old apothecaries, which was bound into a cut made in a patient’s flesh for the purpose of producing inflammation and suppuration, with the notion that such treatment was beneficial, was a minute unripe orange dried, and, no doubt, to some extent, antiseptic.

Besides the introduced trees, we find, in ground which has been more or less under cultivation, and not, therefore, of the nature of the “maquis,” or scrub-land, some beautiful plants, such as the narcissus, iris, and various lilies. One very small and graceful tulip is, I believe, regarded as native to the soil, but a magnificent crimson tulip, as large as the varieties cultivated in English gardens, which I have found abundantly in open park-like land under olive trees at Antibes, is said to have been introduced from Persia in the Middle Ages, and to have taken kindly to the Riviera. It is the Tulipa oculus solis. In the same locality were growing many brilliantly coloured “stellate” anemones.

There is, of course, a third group or “lot” of plants on the Riviera, which consists of those brought from all parts of the world during the past century, and regularly cultivated and cared for in gardens. The climate of the Riviera enables the gardener to grow all sorts of sub-tropical plants in the open air, and a long list of them could be given. The wonderfully brilliant crimson creeper, Bougainvillia, covers walls by the roadways, and even the railway stations, with its rich colour at this season. A delightful book by the distinguished botanist, Professor Strasburger, describing and picturing in colours many of the cultivated as well as the wild plants of the Riviera, has lately been published (in English) at a small price.

The animals which come under the notice of those who go in search of spring sunshine to the Riviera are far less numerous than the plants. But there is one which is dear to all, although it makes such a noise for an hour or so about sunset that some people are irritated or even alarmed by it. This is the little green tree-frog, [Fig. 1], which now comes forth from its winter sleep, and assembles in thousands—guided by the “croak” or “call” which is produced by the males. The females have a very small voice comparatively. I kept two—a male and female—through a winter in London, and when the spring came the male terrified the household one night by unexpectedly uttering his cry—loud and sharp—to which the female replied. “Wharr! biz” is the nearest expression I can give in letters to the two sounds. After a great many evenings spent in these rhythmical declamations, the little frogs collect round pools and tanks, and at last drop from the trees into the water, and there deposit their spawn. When producing his cry the male distends the skin of his throat like a balloon. The air is driven alternately from it into the lungs and back again over the vocal chords, which vibrate with no uncertain sound. These little frogs are easy to keep in an inverted bell-jar or in a fern-case, but must be fed regularly with flies and spiders, which they catch by a sudden dab of the tongue at the moment of alighting from a long leap on to the glass where the insect is crawling. They can hold on to smooth glass or leaves by means of their sucker-like toes ([Fig. 1]).

The colour of the upper surface of the South European tree-frog is a most vivid and smoothly laid-on grass-green. Occasionally the colour becomes altered to a brownish purple, but returns after a day or two to its usual bright green tint. A great rarity is the blue variety of this frog—the enchanted Prince of the Côte d’Azur—blue as the sky and the sea around him—the true genius loci. I obtained one a few years ago at Mentone, and kept it alive for three years in London. Its blue was the blue of the forget-me-not or the finest turquoise. When it died (I believe of old age, and not from discomfort or disease) I examined its skin very carefully with the microscope, and compared it with that of the ordinary green tree-frog, in order to make out the cause of their difference in colour.

Fig. 1.—The little green tree-frog or “rainette” of the Riviera (Hyla arborea). From Professor Gadow’s volume on Reptiles and Amphibia—in the “Cambridge Natural History”—published by Macmillan & Co., by whose permission this figure is here produced.

At Mentone there is a little shop where one may purchase green tree-frogs and ornamental cages in which to keep them. Every year the dealer has two or three specimens of the blue variety on sale—their backs and heads looking like bits of turquoise-blue kid. Visitors have sometimes wrongly supposed that the blue frogs had been artificially changed in colour, but they are real, natural varieties. A similar substitution of blue for green has been noticed as a rare variation in other kinds of frogs and toads in other countries. It really consists in a suppression of yellow pigment.

The interesting thing about the colour of the little tree-frogs is that we find, on careful examination of the skin of a dead specimen with the microscope, that there is no green nor yet any blue “pigment” present in it. I found, on examining the blue specimen which died after living three years with me, that there is only black pigment overlaid by a colourless, semi-transparent layer of skin. In this outer skin in the ordinary green specimens there is scattered a quantity of excessively minute yellow particles, which, mixed with the blue, produce the green appearance. The fact is, that the wonderful “dead” turquoise-blue of the blue frog is a colour-effect similar to that of the blue sky and the blue of the human eye. It is produced by a peculiar reflection of the light from minute colourless particles, without the assistance of any blue-coloured substance. The distinction of these two modes of producing blue colour is important.

Certain transparent bodies are so constituted that when a beam of light is directed so as to pass through them, the red, yellow, green, and purple rays which exist in colourless sunlight are stopped, and only the blue rays come through. Such a body is blue copperas, or sulphate of copper; another is methyl blue, one of the aniline dyes; another is pure water, which gives only a slight advantage to the blue rays, so that the light must pass through a thickness of 30 feet or more before the blue tint is obvious. Thus, part of the blueness of the Côte d’Azur is accounted for—namely, the blueness of the sea when the sunlight is strong and is reflected from the white rocks and sand lying 30 feet to 100 feet below the surface of the water.

There are, of course, other self-coloured transparent bodies which allow only rays of one colour to pass. Thus, blood-red, or hæmoglobin, the pigment of the blood, allows chiefly red rays to pass through it. Yellow rays only pass through a solution of saffron or of chromic acid; green only or chiefly through green copperas (sulphate of iron) or through leaf-green or chlorophyll. Colour is very generally due in natural objects to such transparent bodies which absorb or stop all the coloured rays of light as it passes through them, excepting those of one tint—or, to be more correct, nearly all except those of one tint.

But the blue of the blue frog and a great deal of the blue in nature is due to another cause. If you are a smoker, or the friend of a smoker, watch the fine curling lines of smoke ascending from a cigar when it is being consumed in bright sunshine. You will see that it has a blue, even an azure blue, tint as the sunlight falls upon it. But if you let the smoke get between the sun and your eyes you will notice that the little curling clouds are no longer blue, but reddish-brown, in appearance. The smoke is not a transparent blue; looked at as a transparent body, it is brown! Further, when the smoke has passed into the smoker’s mouth and is ejected after remaining there for a few seconds, the cloud no longer looks blue, even when the sunlight falls on it and is reflected from it to your eye. It is now opaque white or colourless, with, perhaps, a faint tinge of blue. This change is due—as was shown by the experiments of the late Professor Tyndall upon a variety of clouds and vapours—to the cooling of the smoke and the increased size of the floating particles which coalesce as the temperature falls. The larger particles reflect white light, and the cloud is no longer blue. A cloud formed by the finest particles gives the strongest blue to the light reflected from it, and it is to this property of the finest particles of water-cloud floating in our atmosphere that the blue colour of the sky is due.

No doubt the question arises, “Why do clouds of the finest particles reflect a predominant amount of blue light rather than yellow or green or red?” That question is answered by mathematicians in accordance with what is ascertained as to the nature and properties of light, but it would require a long treatise to put those matters even in outline before the reader. We may in the meanwhile accept the conclusions of the physicists, and interest ourselves in seeing how they apply to some of the concrete facts about colour in Nature.

There are other instances of “blueness” due to the reflection of light from a cloud of excessively minute particles besides that of the azure sky and the blue, curling smoke of a wood fire. A familiar instance is the blueness of translucent bodies, such as the “white” of a boiled plover’s egg, especially when a bit of it is placed on a dead-black ground. The bluish appearance of watered London milk is another instance. These bodies look blue owing to the fine, colourless particles suspended in them, which act on light in the same way as do the fine particles of newly-produced smoke. Another very interesting case is the blue colour of the iris of the eye of man and other animals. It is not due to any blue pigment, but to a reflection from fine particles in the translucent, but turbid, tissue of the iris overlying the dark, black chamber of the eye. White geese and white cats frequently have blue eyes, the blue being thus produced. The only pigment which occurs in the human eye is a brown one, which gives a colour varying from amber yellow to very dark brown, almost black, according to the quantity present. When a very little of it is present it gives, in combination with the blue appearance of the unpigmented iris, a green tint, so that green eyes owe their colour to the same combination of causes as does the green skin of the little tree-frogs, or “rainettes.”

No solvent will extract any pigment from the skin of the blue frog—nor by the finest trituration can one obtain any coloured particles from it; only fine black granules can be separated. Alcohol removes the yellow pigment from the skin of a green tree-frog (killed, of course, for the experiment), and for a minute or two the skin becomes blue when its yellow pigment is thus removed by immersion in spirit; but it rapidly becomes a dull greyish-brown in colour, and so remains; the green cannot be preserved in spirit-specimens. It is not fully explained how such a uniform “dead” blue is produced by the reflection of light from fine particles, as that observed in the blue frog’s skin.

It appears that the blue and the green colour in the feathers of birds is in most, if not all, cases produced in the same way as the blue and green of the tree-frog’s skin. It would be interesting were it found possible to produce a full dead-blue colour by experimentally placing a coat of a translucent but turbid colourless medium on a dead-black plate. This, however, has not been done as a deliberate experiment. It is, however, recorded that Goethe was delighted to find what he considered to be a confirmation of his theory of colour when a friend showed him an oil-painting of a gentleman in a black coat which when wetted with a sponge turned bright blue. The picture had been recently “restored,” and the varnish on the black coat was not “dry.” It was precipitated by the water from the sponge, mixing with the spirit which held it in solution. A fine colourless cloud was thus produced overlying the black paint of the coat, and, as in the case of the cerulean frog, a dead-blue colour, due to reflection of the light by the fine particles, was the result. Some friendly physicist might repeat this experiment and study the matter in detail. The red, orange, and yellow colours of birds’ feathers are produced by pigments which are either insoluble or only soluble with great difficulty in fluids of the nature of ether. There is, however, an exception in the case of the African birds called Turacous, or Plantain-eaters. These birds have some large quill-feathers in the wing of a rich crimson colour. This splendid red pigment can be washed out of the feathers by water which is slightly alkaline, and a fine blood-red solution is obtained. Why this curious exception exists we do not know. The extracted colour is found to contain the element copper as one of its chemical components. Plantain-eaters kept in cages have sometimes washed all the colour out of their feathers owing to the water supplied to them for bathing and drinking having become foul and ammoniacal, and thus capable of dissolving the red pigment.

The cultivation on the Riviera of flowers for sale as “cut flowers” in Paris, London, and Berlin, in the colder months of the year, is now an enormous business, bringing many thousands of pounds yearly to the small gardeners around Hyères, St. Raphael, Nice, and Mentone. Roses, violets, carnations, “mimosa” of various kinds, anemones, lilies, and narcissus are sent literally in tons by quick trains several times a week from these realms of sunshine to the dreary North. The commencement of this trade was due to the suggestion made some fifty years ago by Alphonse Karr, the French poet and journalist, who had a beautiful garden of his own at St. Raphael, and found that he could produce flowers in profusion through the winter. Two years ago I visited this garden (which now belongs to a French painter) at the beginning of April, and found it full of interesting flowers and shrubs, enormous bamboos, palm trees, some twenty different “mimosas,” eucalyptus of several species, camellia trees, and rose-bushes in quantity.

The influence of man on the vegetation of a favoured locality like the Riviera is more striking than in the North. But it is worth remembering that the most familiar tree in England—the common elm—is not a native, but introduced from South Europe. Our native elm is the wych-elm, or mountain elm—a much handsomer tree, in the opinion of many, than the so-called “common elm.” There are doubts as to whether both the spruce and the larch were not introduced by man at a very remote time, so that the Scotch fir would be our only aboriginal pine. The oak, beech, birch, ash, hawthorn, poplar, and alder are undoubted native English trees. The holly-oak or evergreen oak, the sycamore, plane-tree, sweet chestnut, horse chestnut, walnut, and probably the lime or linden tree have been introduced by migrating men at various periods into our islands. With the exception of rye and oats none of the plants which we cultivate for food are derived from our own wild plants, and none of our domesticated animals have been produced from native wild kinds.

[VIII]
FRESH-WATER JELLY-FISHES

Most people nowadays know a jelly-fish when they see one—and recognise that it is eminently a product of the sea—one sees them washed up on the seashore, soft discs of transparent jelly of the size of cheese-plates ([Fig. 2]). They have a mouth in the centre of the disc, often at the end of a depending trunk, like the clapper of a bell. Some have tentacles, sometimes yards long, which sting like nettles. They also have eye-spots, an internal system of canals and muscles which enable them to swim by causing the edge of the disc or bell to contract and expand in alternate strokes. There are hundreds of kinds of marine jelly-fish varying in size from a sixpence to that of a dinner table, and until twenty-five years ago none were known to live in ponds, lakes, or rivers. Although they often are carried up estuaries, and may stay for a time in brackish water, or even in fresh water, none were known which really lived and bred in fresh water. They were regarded, as are star-fishes and sea-urchins, as distinctively marine, and debarred by the delicacy of their watery jelly-like substance from tolerating the change from sea water to fresh water as a permanent thing. All fresh-water animals—fishes, shell-fish, cray-fish, worms, and polyps—are derived from closely similar marine animals, are in fact sea-things which have suffered a change, and been able to stand it.

Fig. 2.—The common jelly-fish (Aurelia aurita) one-third the natural size; or, one of the four arms or fleshy tentacles surrounding the diamond-shaped mouth; Tc, one of the eight eye-bearing tentacles at the edge of the disc; GP, opening of one of the four sub-genital pouches, which bring sea-water close to the ovaries and spermaries, which, however, do not open into these pouches; x and y, outline of the sub-genital pouches seen through the jelly.

[Transcriber’s Note: The original image is approximately 2 inches (5cm) in diameter.]

These being our preconceptions about jelly-fish, great was the excitement when, in 1880, hundreds of beautiful little jelly-fish were suddenly discovered briskly expanding and contracting, rising and sinking in the water of a large fresh-water tank in the middle of London ([Fig. 3]). You never know who or what may turn up in London. A badger, a green parakeet, a whale, an African pigmy, an Indian scorpion, and a voice worth ten thousand a year, have all, to my knowledge, been stumbled upon unexpectedly at different times in the highways of London. A new jelly-fish was perhaps one of the least expected “casual visitors.” It was found in the large tank four feet deep in which the great tropical water-lily—the Victoria regia—and other tropical water plants are grown in the Botanic Gardens, Regent’s Park. It came up by hundreds every year for some ten years after its first appearance, dying down in six weeks or so each season.

Fig. 3.—The fresh-water jelly-fish (Limnocodium) enlarged four times linear measurement, as it is seen dropping through the water in a glass jar. PT, one of the four principal tentacles. MR, the margin of the disc. Ve, the delicate muscular frill or velum.

[Transcriber’s Note: The original image is 2¾ inches (7cm) high and 2¼ inches (5.5cm) wide.]

All the specimens were males, and the puzzle was to find out how it reproduced itself. After a few seasons had passed I determined to solve this problem. I made the guess that perhaps the jelly-fish were budded off from a fixed weed-like polyp growing in the depths of the tank—as is the case with many of the marine jelly-fishes. I remember that one leading member of the council, which still presides over the destinies of the Botanic Gardens, confided to me in a hushed whisper his belief that Providence created this new jelly-fish year by year in the tank in honour of the august patroness of the Botanic Society—Her Royal Highness the Duchess of Teck. I was obliged to make an end of this flattering theory when I discovered, after long searching with my assistant—attached to the rootlets of floating water weeds a minute three-branched polyp ([Fig. 4]), from which, as we subsequently were able to observe, the jelly-fish were pinched off as tiny spheres about one-sixteenth of an inch in diameter. No females of this jelly-fish were ever discovered. The polyps lived on from year to year, and budded off each season a swarm of pretty but futile male jelly-fish. They ripened and died on attaining a diameter somewhat less than that of a shilling. There were many most interesting points made out as to their structure, mode of feeding, and growth. You could keep them in a tall glass jar supported over a small gas-jet (they lived best at a temperature of 80° Fahr.), and they would swim up by a series of strokes to the top of the water, and then drop like little parachutes through the eighteen inches of depth to the bottom—taking in water-fleas and such food on the way—and immediately would start upwards again. I used to take them alive in my pocket corked up in a test-tube to show to friends.

Fig. 4.—Four of the minute club-shaped polyps adhering to a root-fibre of a water-plant. The rounded end becomes nipped off and swims away, free, as a young jelly-fish.

After they had disappeared from the tank in Regent’s Park (owing to some unhappy cleaning of the tank) they suddenly, in 1903, appeared—it seems incredible—at Sheffield! Then they briefly showed up in 1905 at Munich, and at Lyons had been captured in 1901—always in a tepid water-lily tank! We never could make out where they came from originally. Of course, the polyp must have been brought into the tank with some bundle of water plants from a tropical lake or river, but we never had any indication as to when or which.

Since the days of the fresh-water jelly-fish of Regent’s Park, which was called (a name, but why should it not have a name?) Limnocodium Sowerbii—a jelly-fish of about the same size ([Fig. 5]) but very different in shape and tentacles—was discovered in the great African fresh-water lake Tanganyika—in enormous numbers, and was named Limnocnida Tanganyikæ. Only five years ago the same jelly-fish was discovered in the Victoria Nyanza, and a little earlier in backwaters of the Niger. It is a curious and significant fact bearing upon the history of these three areas of fresh water connected with the three greatest African rivers—the Congo, the Nile, and the Niger—that the same little jelly-fish is found in all of them.

Fig. 5.—The African fresh-water jelly-fish (Limnocnida) found in Tanganyika, Victoria Nyanza, and the Niger.

And now we have just been reminded of Limnocodium, the Regents Park jelly-fish, from a remote and unexpected source. A thousand miles up the Yang-tse-Kiang River, in China, in the province of Hupi, the Japanese captain of a river steamer, plying there and belonging to a Japanese company, captured ten jelly-fish in the muddy waters of the river. He brought them home, preserved, I suppose, in alcohol or formalin, and they have been described by Dr. Oka, a Japanese zoologist of Tokio, in a publication bearing the Latin title Annotationes Zoologicæ niponenses, issued in December 1907. European sea captains have not rarely been ardent naturalists, but I think the Japanese is the first captain of a river steamboat who has discovered a new animal on his beat. I have not heard of Mississippi steamboat captains amusing themselves in this way—other rivers, other tastes.

Dr. Oka describes the jelly-fish thus brought to him as a Limnocodium, differing in a few details from that of Regent’s Park, so that he distinguishes this Chinese species as Limnocodium Kawaii, naming it after the naturalist captain, who must have a rare taste for picking up strange and new things, and a rare goodwill in bringing them home with him. So here is another fresh-water jelly-fish, for it is not the same as the Regent’s Park one, though closely like it. Possibly Limnocodium is an Asiatic genus, and the original Sowerby’s Limnocodium will be found in another Chinese river. But it may prove to be South American, as is the water-lily Victoria regia.

A very small fresh-water jelly-fish was found some twelve years ago—in 1897—in the Delaware River at Philadelphia, United States, and was lately described by the well-known naturalist, Mr. Potts. It was budded off from a very minute polyp resembling that found in the Regent’s Park, but the jelly-fish was totally different from Limnocodium. Only four or five specimens of this jelly-fish have ever been seen, and the Philadelphian naturalists ought certainly to look it up again.

An account of the Philadelphian jelly-fish and of other fresh-water jelly-fishes, with illustrative plates, will be found in the Quarterly Journal of Microscopical Science, 1906. Mr. Charles Boulenger has, in the same Journal, 1908, described yet another fresh-water jelly-fish from the Fayoum Lake in Egypt.

[IX]
THE STORY OF THE COMMON EEL

Though the Scotch Highlanders are said to have a profound objection to eating eels on account of the resemblance of these fish to snakes (not a very good reason, since the quality and not the shape of what one eats is the important thing), yet eels have been a very popular delicacy in England in past days. Eel-pie Island, at Richmond, is known to most Londoners, and eel-pie shops were familiar in London less than a century ago. A good Thames eel is still appreciated by the few people who nowadays take some small amount of intelligent interest in what they eat. Abroad, eels are still popular. Eel-traps are still worked in the rivers. In such districts as the flat country, on the shores of the Adriatic, near Venice, millions of young eels are annually “shepherded” in lagoons and reservoirs, and reared to marketable size. The inland eel-fisheries of Denmark and Germany are carefully regulated and encouraged by the Government in those States.

The fact is that railways, ice-storage, and steam-trawling have, in conjunction, revolutionised our habits in regard to the use of fish as a daily article of diet. Fresh-water fish are now almost unknown as a regular source of food in the British Islands. The splendid fish of the North Sea, the Channel, and the Atlantic coast have pushed them out of the market. Thirty-eight years ago, when I was a student in Leipzig and Vienna, “baked carp” was the only fish to be had in the dining-rooms we frequented. Once a week there were fresh haddock, for those who fancied them, in the celebrated Auerbach’s Keller. Now the railway and packing in ice have brought North Sea fish to the centre of Europe, and created a taste for that excellent food. Even on the Mediterranean at Nice, I lately saw North Sea turbot, soles, and haddock lying on the marble-slabs in the fish market side by side with the handsome but small bass, mullet, gurnards, and sea-bream of the local fishery, and the carp, pike, trout, and eels of the fresh waters of the South of France.

Nevertheless the eel—the common fresh-water eel—is still valued on the Continent, as is proved by the fact that the German Imperial Government has recently sent an important official of the Fisheries Department to Gloucester in order to make extensive purchases of the “elvers,” or young eels which come up the river Severn in millions at this season. The purpose of the German fisheries officials is to place many hundred thousands of these young eels in German rivers which are not so well supplied by natural immigration as is the Severn, and by so doing to increase the supply of well-grown eels hereafter in the river fisheries of North Germany.

This interesting practical attempt to increase the supply of eels in Germany will be further appreciated when I relate what has been discovered within the last twenty years as to the reproduction, migrations, and habits of the common fresh-water eel. It has been known, time out of mind, that in the early months of every year millions of young eels a little over two inches in length, called “elvers” in English and “civelles” in French, come up the estuaries of the rivers of Europe in a dense body. They are so closely packed together as the narrower parts of the stream are reached, that thousands may be taken out of the water by merely dipping a bucket into the ranks of the procession. I obtained a few thousand of these “elvers” lately from the Severn and placed them on exhibition in the central court of the Natural History Museum in London. The Anglo-Saxon name “eel-fare” is given to this annual march or “swim” of the young eels from the sea to the fresh waters.

Though riverside folk have never doubted that the elvers are young eels which have been hatched from spawn deposited by parent eels in the sea, and are “running up” to feed and grow to maturity in the rivers and streams inland, yet country folk away from the big rivers have queer notions as to the origin and breeding of eels. They catch large, plump eels a couple of feet long in stagnant ponds hundreds of miles from the sea, far from rivers, and more than a thousand feet above the sea-level. They have no notion that those eels originally “ran up” as little eels from the sea, nor that many of them make their way across wet grass and by rain-filled ditches back to the rivers and to the sea when they are seven years old. But that is now known to be the fact. Just as there are fish, like the salmon, which “run down” to the sea to feed and grow big and “run up” to breed in the small pools and rivulets far from the river’s mouth, so there are other fishes, of which the eel is one, which run up to feed and grow and run down to breed—that is to say, to deposit and fertilise their eggs in the depths of the ocean.

Fishermen who work river-fisheries for eels (far more valued abroad than in England) distinguish “yellow eels” and “silver eels” (see [Plate I.] opposite title page). We used to distinguish also snigs and grigs, or narrow-nosed and broad-nosed eels (probably males and females). The remarkable fact, admitted by both fishermen and anatomists, was that you could not really tell male from female, nor, indeed, ever find an eel (that is, a common eel, as distinguished from the much larger and well-known conger eel) which was ripe, or, indeed, showed any signs of having either roe or milt within it. A popular legend exists that eels are produced by the “vivification” of horse-hair. Occasionally in summer a long, black, and very thin threadworm (called Gordius by naturalists) suddenly appears in great numbers in rivers, and these are declared by the country-folk to be horse-hairs on their way to become eels! I remember a sudden swarm of them one summer in the upper river at Oxford. Really, they are parasitic worms which live inside insects for a part of their lives, and leave them in summer, passing into the water. Fanciful beliefs about aquatic creatures are common, because it is not very easy to get at the truth when it is not merely at the bottom of a well but at the bottom of a river or of the deep sea! The fishermen of the east coast of Scotland, who think very highly of their own knowledge and intelligence, believe that the little white sea-acorns or rock-barnacles are the young of the limpets which live side by side with them, and are scornful of those who deny the correctness of what they consider an obvious conclusion!

A few years ago the Scandinavian naturalist, Petersen, showed that the “silver” eels are a later stage of growth of the “yellow” eels; that they acquire a silvery coat, and that the eye increases in size—as a sort of “wedding dress,” just before they go down to the sea to breed. I owe to Petersen’s kindness the coloured drawings of the heads of the yellow and the silver eel reproduced in [Plate I]. These silver eels are caught in some numbers about the Danish coast and river mouths, moving downwards; and Petersen has been able to distinguish the males from the females by finding the still incompletely formed milt and roe within the silver eels. Not only that, but one of Petersen’s assistants at the Danish Biological Station has found that you can tell the age of an eel by the zones or rings shown by its scales, when examined with a microscope, just as the age of trees can be told by the annual rings of growth in the wood. Most people, even if familiar with eels, even cooks who have skinned an eel, do not know that they have scales; but they have,—very small ones. The age of other fishes has been similarly ascertained by annual zones of growth marked on the scales; and lately the age of plaice has been found to be conveniently given by zones of growth formed annually on the little ear-stones which we find in the liquid-holding sac of the internal ear. I am afraid many of my readers will be surprised to learn that fishes have an internal hearing apparatus similar to our own, also that they have olfactory organs, and, in some cases, a well-grown tongue!

The power thus obtained of telling the age of an eel has led to the following knowledge about them, namely, that female eels do not become “silver” eels and “run down” before they are seven years old, and often not till eight and a half years of age, or even sometimes eleven or twelve years, when they are nearly 3 feet long. The male eel becomes “silver” (instead of “yellow”) at an earlier age—four and a half years,—and rarely defers his nuptial outburst until he is seven or eight years old. The females of the same age are larger than the males; a usual size for silver females of seven years old is a little over 2 feet, and of a silver male of the same age 20 inches.

The further facts which I am about to relate as to the migration and reproduction of the common eel are of great interest. The common “yellow” eels of our ponds and rivers, as we have seen, when they are from five to seven years old and over, put on, as it were, a wedding dress. They become “silver” eels, and descend the rivers to the sea. There they produce their spawn. The young eels thus produced, when only 2 inches long, leave the sea. Every year they ascend the estuaries and rivers of Europe as “elvers” in enormous numbers, their procession up the rivers being known as “the eel-fare.”

Some eels, shut up in moats and ponds, never escape—they become more or less “silver” and restless, but fail to get away. Others crawl up the banks in wet, warm weather, when the ponds are full to the brim, and over the meadows. They are found sometimes on their journey when they

“... have to pass

Through the dewy grass,”

and so to the river, and on to the marriage feast in the deep sea. The fact is, that usually eels inhabit in large numbers the rivers and streams, and have no difficulty in getting down to the sea when they are adult. Those who, as young elvers, have wandered far off into sunken ponds and reservoirs, are eccentric spirits who have lost the normal way of life; like fellows of colleges in the old days, they have cut themselves off from the matrimonial “running down,” but they have compensations in quietude, abundant food, and a long life.

We now know where the silver eels go when they run down the rivers. They go into the sea, of course; but we know more than that. It has now been discovered that they make their way for many miles along the sea-bottom—in some cases hundreds of miles—to no less a depth than 500 fathoms. In the Mediterranean they don’t have very far to go, for there is very deep water near the land, and Professor Grassi found evidence of their presence in the depths of the Straits of Messina. But the eels of the rivers which empty into the North Sea and English Channel have much farther to go; they have to go right out to the deep water of the Atlantic, off the west coast of Ireland. That is the nearest point where 500 fathoms can be touched; there is no such depth in the North Sea nor in the Channel. They never come back, and no one has ever yet tracked them on their journey to the deep water. Yet we know that they go there, and lay their eggs there, and that from these remote fastnesses a new generation of eels, born in “the dark unfathomed depths of ocean,” return every year in their millions as little “elvers” to the rivers from which their parents swam forth in silver wedding dress. Soon, we have reason to hope, by the use of suitable deep-sinking nets, we shall intercept, in the English Channel, some of the silver eels on their way to the Atlantic deeps. They must go in vast numbers, and yet no one has yet come across them. How, then, do we know that the silver eels ever go to this 500-fathom abysm?

Fig. 6.—Young stages of the common eel, drawn of the natural size by Professor Grassi. A, The Leptocephalus, transparent stage. D, the elver, or young eel, which is coloured, and of much smaller size than the transparent, colourless creature by the change of which it is produced. It is the elver which swims in millions up our rivers. B and C are intermediate stages, showing the gradual change of A into D.

[Transcriber’s Note: The original image “A” is approximately 2¾ inches (7cm) long and ½ inches (1.25cm) wide.]

The answer is as follows: A very curious, colourless, transparent, absolutely glass-like, little fish, 2½ inches long, oblong and leaf-like in shape, has been known for many years as a rarity, to be caught now and then, one at a time, floating near the top in summer seas ([Fig. 6]). I used to get it at Naples occasionally many years ago, and it has sometimes been taken in the English Channel. It is known by the name “Leptocephalus.” Placed in a glass jar full of sea-water it is nearly invisible on account of its transparency and freedom from colour. Even its blood is colourless. The eyes alone are coloured, and one sees these as two isolated black globes moving mysteriously to the right and the left as the invisible ghostly fish swims around. Twenty years ago one of these kept in an aquarium at Roscoff, in Brittany, gradually shrunk in breadth, became cylindrical, coloured and opaque, and assumed the complete characters of a young eel! To cut a long story short, these Leptocephali were found twelve years ago in large numbers in the deep water (400 fathoms) of the Straits of Messina by the Italian naturalists Grassi and Calandruccio, and they conclusively showed that they were the young phase—the tadpole, as it were—of eels. They showed that different kinds of eels—conger eels, the Muræna, and the common eel—have each their own kind of transparent “Leptocephalus-young-phase,” living in but also above the very deep water, in which they are hatched from the eggs of the parent eels. The Leptocephalus-young when hatched, grow rapidly, and ascend to near the surface immediately above the deep water, and are caught at depths of ten to a hundred fathoms. To become “elvers,” or young eels, they have to undergo great change of shape and colour, and actually shrink in bulk—a process which has now been completely observed and described. It is not surprising that their true nature was not at first recognised. The proof that the silver eels of North and West Europe go down to the 500-fathom line off the Irish coast, in order to lay their eggs, is that the Danish naturalist Schmidt and his companions discovered there two years ago, above these great depths (and nowhere else), by employing a special kind of fine-meshed trawling net, many thousands of the flat, glass-like “Leptocephalus-young-stage,” or tadpole of the common eel, and traced them from there to their entrance into the various rivers. They showed that the Leptocephali gradually change on the way landward into eel-like “elvers.”

The rivers nearest the deep water, such as those opening on the west coast of Ireland and on the Spanish and French shores of the Bay of Biscay, get their elvers “running up” as early as November, December, and January. The farther off the river the farther the elvers have to travel from the deep-sea nursery, so that in Denmark they don’t appear until May. Not the least curious part of the migration of the eel is the passage of the young elvers into the higher parts of rivers and remote streams. They are sometimes seen a hundred miles from the sea, actually wriggling in numbers up the face of a damp rock or wall ten or fifteen feet high, pushing one another from below upwards, so as to scale the obstacle and reach higher waters, like Japanese soldiers at a fort. I found them (so long ago that I hesitate to name the date—it was a year of cholera in London, followed by a great war) in a little rivulet which comes down the cliff at Ecclesbourne, near Hastings, close to a cottage frequented at that time by Douglas Jerrold. They were wriggling up in the damp grass and overflow of the driblet 150 feet above the shore, a stone’s throw below. They must have come out of the sea, attracted by the tiny thread of fresh water entering it at this spot.

The Danube and its tributary streams contain no eels, although the rivers which open into the Mediterranean are well stocked with them. This is supposed to be due to the fact that the Black Sea does not afford a suitable breeding-ground, and that the way through the Dardanelles is closed to eels by some natural law, as it has been to warships by treaty. Probably, however, it will be found that the geological changes in the area of sea and land are intimately connected with the migrations of the eel, and that the eel is originally a marine fish which did not in remote ages travel far from the deep waters. Its gradually acquired habit of running up fresh waters to feed has led it step by step into a frequentation of certain rivers which have become (by changes of land and sea) inconveniently remote from its ancestral haunts. An interesting question is whether at the not very distant period when there was continuous land joining England to France and the Thames and the Rhine had a common mouth opening into the North Sea, eels existed in the area drained by those two rivers; and, if so, by what route did they pass as silver eels to the deep sea, and by what route did the new generations of young eels hatched in the deep sea travel to the Thames and Rhine. It seems most probable that in those days there were no eels in the Thames and other North Sea rivers.

Our present knowledge of the romantic history of the common eel of our own rivers we owe in large part to the work done by the International Committee for the Investigation of the North Sea. Who would ever have imagined when he caught a wriggling eel, with a hook and worm thrown into a stagnant pool in the Midlands, that the muddy creature was some five or six years ago living as a glass-like leaf-shaped prodigy in the Atlantic depths, a hundred miles from Ireland? Who would have dreamed that it had come all that long journey by its own efforts, and would probably, if it had not been hooked, have wriggled one summer’s night out of the pond, across wet meadows, into a ditch, and so to the river, and back to the sea, and to the far-away orgy in the dark salt waters of the ocean-floor, to the consummation of its life and its strange, mysterious ending?

There are two points of interest to be mentioned in regard to the rivers Danube and Thames in connection with eels. I have trustworthy reports of the very rare occurrence of eels in streams connected with the Danube. Since the young elvers do not ascend the Danube, where do these rare specimens come from? There can be no doubt that they have made their way individually into the Danube “system” by migration through canals or ditches from tributaries of the Rhine or the Elbe. A similar explanation has to be offered of the eels which at present inhabit the Thames. I cannot find any evidence of the existence to-day of an “eel-fare”—that is, “a running up of elvers” in the river Thames. Probably about the same time as the foul poisoning of the Thames water by London sewage and chemical works put an end to the ascent of the salmon (about the year 1830), the entrance of the myriad swarm of young eels in their annual procession from the sea also ceased. The elvers were caught and made into fish-cakes in London before the nineteenth century, just as they are to-day at Gloucester. It would be interesting to know exactly when they ceased to appear in the Thames. A curious fact, however, is that young eels—not so small as “elvers,” but from three inches in length upwards—are taken close above London even to-day. Four years ago I obtained a number of this small size from Teddington. The question arises as to whether these specimens represent just a small number of elvers which have managed to swim through the foul water of London and emerge into the cleaner part of the river above. This is improbable. It is more likely that they have come into the Thames by travelling up other rivers such as the Avon—which are connected by cuttings with the Thames tributaries. But it certainly is remarkable that eels of only three inches in length—and therefore very young—should have managed to get not merely “into” the Thames (to the upper parts of which no doubt many thus travel and remain during growth), but actually “down” the Thames so far in the direction of its tidal water as is Teddington lock. The specimens from Teddington were placed by me in the Natural History Museum.

[X]
MODERN HORSES AND THEIR ANCESTORS

The ever-increasing development of motor traffic leads to speculation as to what is to be in the immediate future the fate of the horse. What is its history in the past?

It is in nearly all cases a matter of great difficulty to trace the animals and plants which mankind has domesticated or cultivated to the original wild stock from which they have been derived. Lately we have gained new knowledge on the origin of the domesticated breeds of the horse. It is generally agreed that the Mongolian wild horse represents the chief stock from which the horses of Europe and those conveyed by Europeans to America were derived. This wild horse was formerly known as inhabiting the Kirghiz steppes, and was called the Tarpan. It became extinct there some seventy years ago. The natives of that district asserted that the pure breed was only to be met with farther East in the Gobi Desert of Central Asia. The Tarpan itself showed signs of mixed blood in having a mouse-coloured coat, which is a sure indication amongst horses of cross-breeding. Prevalsky, a Russian traveller, was the first to obtain specimens of the pure-bred wild horse of the Gobi Desert, which still exists. Live specimens have been brought to Europe, and some are in the possession of the Duke of Bedford. A female is mounted and exhibited in the Natural History Museum, and also a skeleton and skulls. Prevalsky’s horse, or the Mongolian wild horse, is of small stature, standing about twelve hands at the shoulder. The root of the tail is short-haired, the mane short and upright, without forelock. The body colour is yellow dun, the mane and tail black, as well as the lower part of the legs, and there is a dark stripe down the back. The muzzle in pure-bred specimens is white. The head is relatively large and the muzzle thick and relatively short. A very decided character is shown by the great size and relative length of the row of cheek-teeth, it being one-third larger than the same row of teeth in a Dartmoor pony of the same stature.

A very interesting fact, which goes a long way to establish the view that the European domesticated horse is derived from the Mongolian wild horse, comes to us in a most striking way from some of the most ancient records of the human race. In the South of France the contents of caves formerly inhabited by men have been dug out and examined with increasing care and accuracy of late years, though first investigated fifty years ago. Similar caves, though not so prolific of evidences of human occupation, have been explored in England (Kent’s Cavern at Torquay, and others). The astounding fact has now become quite clear that these caves were inhabited by men of no mean capacity from 50,000 to 250,000 years ago, when bone harpoons, flint knives, flint scrapers, and bone javelin-throwers were the chief weapons in use, when these islands were solidly joined to the European continent, when a sheet of glacial ice, alternately retreating and extending, covered the whole of Northern Europe, and when the mammoth, rhinoceros, hyena, lion, bear, bison, great ox, horse, and later the reindeer, inhabited the land and were hunted, eaten, and utilised for their bone, tusks, and skin by these ancient men. I revert to this subject in a later article ([page 371]), but would merely say now that it is all as certain and well-established a chapter in man’s history as that of the ancient Egyptians, who are really quite modern (dating from 8000 years at most) as compared with these cave-men of 50,000 years ago, and the even earlier races which preceded them in Europe.

The bones of the animals killed and eaten by the cave-men are found in some cases in enormous quantities. In one locality in France the bones of as many as 80,000 horses (which had been cooked and eaten) have been dug up and counted! The most wonderful and extraordinary thing about these cave-men is that they carved complete rounded sculptures, high reliefs, low reliefs, and line-engravings on mammoth’s ivory, on reindeer horn, on bones, and on stones—the line-engravings being the latest in date, as shown by their position in the deposits on the floor of the caves, which are often as much as twenty feet or thirty feet in thickness! Not only that, but these carvings are often real works of art, extremely well drawn, and showing not mere childish effort but work which was done with the intention and control of an artist’s mind.

An immense number of these carvings are now known. I have before me one of the most recent publications on the subject—a series of plates showing the carvings collected from caves in the Pyrenees, the Dordogne, and the Landes by M. Piette, who recently died. I have examined his collection and others of the same kind in the great Museum of St. Germain, near Paris. We have in London some of the earlier collections, and especially that of the Vicomte de Lastic, to purchase which my old friend Sir Richard Owen journeyed to the Dordogne in the winter of 1864. Many animals, as well as some human beings ([Fig. 7]), are represented in these carvings—the mammoth itself, carved on a piece of its own ivory, is among them, and a good many represent the horse ([Fig. 8]). Now it is a fact that the carvings of the horses of that period undoubtedly represent a horse which is identical in proportions, shape of head, mane, and tail, with the wild Mongolian horse, and is unlike in those points to modern European horses, or to the Arabian horse.

Fig. 7.—Drawing (of the actual size of the original) of an ivory carving (fully rounded) of a female head. The specimen was found in the cavern of Brassempouy, in the Landes. It is of the earliest reindeer period, and the arrangement of the hair or cap is remarkable.

[Transcriber’s Note: The original image is approximately 1½ inches (4cm) high and ¾ inches (2cm) wide.]

Fig. 8.—Drawing (of the actual size of the original) of a fully rounded carving in reindeer’s antler of the head of a neighing horse. The head resembles that of the Mongolian horse. This is one of the most artistic of the cave-men’s carvings yet discovered. It is of the Palæolithic age (early reindeer period), probably not less than fifty thousand years old. It was found in the cavern of Mas d’Azil, Ariège, France, and is now in the museum of St. Germain.

[Transcriber’s Note: The original image is approximately 2¼ inches (5.5cm) wide and 1 inch (2.5cm) high.]

It was, until the discoveries of M. Piette, held that though the cave-men killed, ate, and made pictures of the horse of those remote days, yet that they did not tame it, put a halter or a bridle on it, and make use of it. Some of the carvings figured by M. Piette leave, however, no room for doubt that the cave-men fitted a bridle to the head and muzzle of the horse. These carvings ([Fig. 9]) show a twisted thong placed round the nose and passing near the angle of the mouth where it is possible, though not certain, that a “bit” was inserted. Connected to this main encircling thong are four twisted cords (on each side of the head), which run horizontally backwards, and the two lower of these are joined by a flat, plate-like piece, which is ornamented. The whole apparatus is further connected to a twisted cord on each side, which runs towards the back of the head, but it is not shown in the carving what becomes of it. Thus it seems clear not only that the cave-men of these remote ages were wonderful artists, but that they mastered and muzzled the horse.

Fig. 9.—Drawing (of the actual size of the original) of a flat carving in shoulder-bone, of a horse’s head, showing twisted rope-bridle and trappings. a appears to represent a flat ornamented band of wood or skin connecting the muzzling rope b with other pieces c and d. This specimen is from the cave of St. Michel d’Arudy, and is of the reindeer period. This, and others like it, are in the museum of St. Germain.

[Transcriber’s Note: The original image is approximately 1¾ inches (4.5cm) wide and 1¼ inches (3cm) high.]

Some of the engravings of horses’ heads seem to indicate the existence of a horse alongside the commoner form with a narrower, more tapering face, and may possibly be due to the introduction, even at that remote period, of another race distinct from the Northern or Mongolian wild horse. That this admixture of a distinct and more slender horse with the Northern horse has taken place over and over again in historical times is a matter of knowledge. The question is, when did it first take place, and where did the more slender horse come from? In later days we know this more shapely breed as the Arab and the Barb, and the introduction of its blood at various times into the more Northern stock is well ascertained. The latest great historical case of such admixture is the production of the English thoroughbred in the eighteenth century by such sires as the Darley Arabian, the Godolphin Barb, and the Brierley Turk, whose blood is transmitted to modern racehorses through the great historic sires, Herod, Matchem, and Eclipse, the ancestors of practically all modern racehorses.

The horse of more Southern origin thus recognised as distinct from the prehistoric European horse, it is now convenient to speak of as the Southern or Arabian horse. There are certain curious structural features which seem to mark these horses and their offspring, even when their strain is blended with that of the more Northern horse. Probably from the time of the cave-men onward the selective breeding of horses has been carried on, so that in many breeds size has been vastly increased. It is an important fact that the English racehorse has never been selected and bred for “points” (as cattle and sheep are), but always by performance on the racecourse. Thus it becomes an extremely interesting matter to see what are the changes which the breeder of thoroughbred stock has unconsciously produced—what are the differences between the racehorse of to-day and that of 50, 100, and 150 years ago. This was pointed out to me by the late Duke of Devonshire as a reason for supporting my proposal to secure and place in the Natural History Museum the skulls, limb-bones, hoofs, and other indestructible parts of great racehorses (and of other breeds), and also for having very accurately measured reduced models made of such horses, in order that we may after some years compare the proportions and structure at present arrived at with the later developments which the continual selection of winner’s blood in breeding must unconsciously produce. Such a collection was started by me in the museum, but it needs the assistance of owners of horses—both as to placing record specimens in the museum and in paying for the preparation of accurately reduced models by competent artists. It already comprises the skulls of Stockwell, Bend Or, and Ormonde, and several carefully made reduced models of celebrated horses. There is no doubt that the English racehorse has increased in size. He is a bigger animal to-day than he was 200 years ago, and the opinion of the best authorities is that he has increased on the average an inch in height at the withers in every twenty-five years. The racehorse has a much longer thigh-bone and upper-arm bone (in proportion to the rest of the leg) than has the cart-horse, and it is probable that this length has been continually increased by the selection of winners for breeding.

There are other points of scientific interest as to modern horses and their forefathers which are illustrated by valuable specimens and preparations placed by me in the Natural History Museum.

All those hairy warm-blooded quadrupeds which suckle their young, and are hence called mammals, are the descendants of small five-toed ancestors about the size of a spaniel. This is equally true of the elephant, the gorilla, the horse, and the ox. In the sands and clays deposited since the time of the chalk-sea, the remains (bones and teeth) of the ancestors of living mammals are found in great abundance. These sands and clays are called “the Tertiaries,” and are divided into lower, middle, and upper—whilst we recognise as “Post-Tertiaries” (or Quaternary) the later formed gravel and cave deposits in which the remains and weapons of the cave-men have been found. The Tertiaries consist of a series of deposits amounting to about 3000 feet in thickness, and they have taken several million years in depositing—no one can say how many.

HIPPARION HORSE

Fig. 10.—To the left, the fore-foot of the horse-ancestor, Hipparion, showing three toes: to the right, the back view of a long bone of a modern horse’s foot, with rudiments of outer toes, called splint-bones.

In the upper Tertiary we find the remains of a kind of horse (the Hipparion), with well-developed “petti-toes” (like those of a pig) on each side of the big central toe ([Fig. 10]). In the middle Tertiary we find smaller ancestral horses, with three toes of nearly equal size, and in the lower Tertiary a horse-ancestor as small as a fox-hound (the Hyracotherium), with four toes on its front foot and three on its hind foot. Coming very close to this in general character is another small extinct animal of the same age, with five toes on each foot. As the toes have dwindled in number and size, leaving at last only the big central toe (as we pass upward from the small ancestors to the big modern horse), so the cheek-teeth, too, have changed. At first they had shallow crowns and divided fangs, and showed four prominences on the crown which were little, if at all, worn down during life. But as the horse became a bigger animal and took to eating coarse tooth-wearing grass, his teeth became deeper, and continued to grow for a long time, whilst the crown was rubbed down by the hard food, and a curiously complex pattern was brought into view by the exposure of the irregular bosses of the crown in cross section. And, meanwhile, the size and proportions of the horse-ancestors changed until, after being pig-like, then tapir-like, they acquired the perfect form and size for fleet and prolonged movement over firm, grass-grown plains. Horses and other large animals have to run, not only to escape pursuit by carnivorous enemies, but in order to travel, before they die from thirst, from a region suddenly dried up by drought to a region where water can be had. Many thousands of wild animals perish every year from local droughts in Africa. No small animals can exist in regions liable to be affected by sudden drought.

Three-toed horses, like the upper Tertiary Hipparion, are occasionally born as “monstrosities” from ordinary horses at the present day. All horses have the remnant of a toe on each side of the big central toe—in the form of splint-bones—concealed beneath the skin. In some breeds, for instance, in the “Shire” horses, which have enormous hairy feet in proportion to their huge strength and weight, these splint-bones tend to develop three little toe-joints, which are immovable, but obviously are “petti-toes.” It is related by Suetonius that Julius Cæsar used to ride a favourite horse which had several toes on each foot with claws like a lion. This was one of the “monstrosities” alluded to above, a throw-back to the ancestral many-toed condition. Specimens illustrating these, and all else which I am here relating concerning horses, and much more which I have not space to tell, may be seen in the North Hall of the Natural History Museum.

Fig. 11.—Skulls of horses and of deer to show the pre-orbital pit or cups pf, and its absence in the Mongolian (Prevalsky’s) horse.

The three-toed ancestral horse, Hipparion, attained a fair size (that of a big donkey), and was shaped like the recent fleet one-toed horses. In the skull in front of the orbit, the Hipparion has a strongly marked depression in the bone, as long and broad as a hen’s egg, and in shape like one-half of an egg cut through longwise (see [Fig. 11] pf). These pre-orbital cavities are known in deer, sheep, and antelopes; they lodge a gland resembling the tear-gland, which has, itself, a separate existence. Similar “glands” are found in the feet and ankle-joints of sheep and deer. The fluid which they secrete probably has an odour (not readily noticed by man) which helps to keep the herd together, or, on certain tracks when the fluid is smeared on to herbage. It is a remarkable fact that the skulls of the wild Mongolian horse and of the fossil horse of the cave-men, as also those of the commoner European breeds, have no trace of this pre-orbital cup or of the gland which Hipparion, their three-toed ancestor, possessed. Nor, indeed, have the asses and zebras. But the Southern horse, the Arab, and all the breeds into which his blood has prominently entered—as, for instance, the English racer (so-called “thoroughbred”) and the “Shire” horse (which is derived from the old English war-horse, in the making of which certainly four hundred years ago Arab blood and heavy Northern stock were mingled), do show, as a rule, a well-marked if shallow, cup-like depression in front of the orbit! In fact, as Mr. Lydekker has pointed out, the presence of this “pre-orbital cup” is evidence of the descent of its possessor from Arab ancestry. Many specimens of horses’ skulls showing this “cup” are exhibited in the Natural History Museum. We have not been able to find any trace of a gland like the “larmier” of deer and the “crumen” of antelopes on examining the soft tissues which overlie this cavity in horses of Arab descent, but it is not improbable that occasional instances of such survival will some day come to light. A very interesting fact in connection with this concavity and its indication of a distinction between the Northern (Mongolian) and the Southern (Arabian) horse is that in India a fossil horse of very late Tertiary date has been found, a true one-toed horse, not a Hipparion, which has the pre-orbital cup well marked, and is possibly the ancestor of the Arab.

There is no very great difference between the wild horse and wild asses and zebras. They are distinct “species,” but will breed together and produce “mules,” which in rare cases appear to be themselves fertile, although this is doubtful. The inner causes of the infertility of mules are not really known or understood. Nor, in fact, do we know really and experimentally what are the causes of fecundity and of infecundity in normally paired animals, including mankind. It is of the utmost importance to modern Statecraft that this subject should be studied, and there is a great field for experimental inquiry.

A clear mark of difference between the horse and the other species of the genus Equus (namely, the Asiatic and African asses and the zebras) is found in the curious wart-like knobs[1] on the legs, which are called “chestnuts.” These warty knobs appear to be the remains in a “dried up” condition of glands, such as are found in the legs of deer in a similar position, and secrete a glairy fluid. In new-born colts they sometimes exude a fluid, and also more rarely in adult horses. The fluid attracts other horses (probably by its smell), and also causes dogs to keep quiet. The horse has one of these wart-like “chestnuts” above the wrist joint (so-called knee) on the inner side of the fore-leg. And so have all the asses and zebras. But the horse ([Fig. 12]) has also a similar “chestnut” on the inner side of each of its hind-legs, below the heel-bone, or “hock.” This hind-leg chestnut is absent in all asses and zebras. This difference between the horse and ass can be tested by my readers on any roadside by their own observation. The hind-leg chestnut is also absent in certain breeds of ponies from Iceland and the Hebrides. Its presence and absence are interesting in connection with the disappearance of the face-gland or pre-orbital gland in all recent horses, asses, and zebras.

Fig. 12.—Fore and hind legs of horse and ass, to show the “chestnuts,” and the absence of that structure from the hind-leg of the ass.

The “chestnuts” of the horse have sometimes been compared erroneously to the “pads” on the feet of other animals, and supposed to be survivals of a “pad” in each foot corresponding to the inner of the three toes of the Hipparion. The real representative, in the horse, of the chief pad of the foot of animals which do not (as the horse does) walk on the very tip of the toe, is a little knob called the “ergot.” The diagram, [Fig. 13], shows how this ergot corresponds to the chief pad of the three-toed tapir’s foot, and so to that of the dog also.

Fig. 13.—Diagram of the under surface of the foot in the dog, tapir, and horse, to show that the horny knob of the horse’s foot, called the “ergot,” corresponds to the central “pad” of the other two.

The absence of living horses, or of any kind of ass or zebra, from the American Continent, when first colonised by Europeans in the sixteenth century, is a very singular fact. For we find a great number and variety of fossil remains of extinct horses in both North and South America. It seems possible that some epidemic disease swept them from the whole Continent not very many centuries before Europeans arrived—for there is evidence in South America of the co-existence there of peculiar kinds of horse with the “Indian” natives. It is even alleged that Cabot, in 1530, saw horses in Argentina, which were the last survivors of the native South American species. And it is also said that the Araucanian Indians of Patagonia have a peculiar breed of ponies, which may be derived in part from a native South American stock. I have never been able to procure a skull of this breed, or any detailed description of it. What is quite certain is that in the great cave of Ultima Speranza, in Patagonia—from which the hairy skin, dried flesh and blood, and unaltered dung as well as the bones, of the giant sloth Mylodon were obtained—a great number of the horny hoofs, and the teeth of a peculiar horse were also found some eight years ago, and are preserved in the Natural History Museum, together with the remains of the giant sloth. The condition of these remains is such that they cannot be many centuries old. The animals appear to have been contemporaneous with an early race of Indians who made use of the cave before the arrival of Europeans. A skull of one and a skeleton of another of the peculiar extinct South American horses (called Onohippidium and Hippidium), which survived until a late period in Patagonia and may possibly have been seen by Cabot, are shown in the Natural History Museum. Their bones are found in the superficial gravel and sand of the pampas.

To revert for a moment to the history of the English thoroughbred. It appears that in England in the middle of the eighteenth century a happy new infusion of the Arab race with that of existing stock (which already contained some Arab blood mixed with that of the Northern race) produced once and for all a very perfect and successful breed. That breed did not derive speed from the Arab, but “stamina,”—probably a powerful heart. It did not derive its size from the Arab, but the cross proved to be a large horse. It has never been improved since by any further admixture of Arab or Southern blood. Hence the (at first sight) misleading name “thoroughbred.” This name is not intended to imply that the breed is not originally a “blend,” but that those horses so called are pure-bred from the happy and wonderful mixture which a hundred and fifty years ago was embodied in the great sires Matchem, Herod, and Eclipse.

FOOTNOTES:

[1] The names “malander” and “salander” have been recently applied by zoological writers, apparently by misconception, to these “callosities” or “chestnuts.” Those names are used by veterinary surgeons to describe a diseased condition of this part of the horse’s leg (Italian “mal andare”), and do not apply to the “chestnut” itself, which is sometimes called “castor.”

[XI]
A RIVAL OF THE FABLED UPAS TREE

We are so accustomed nowadays to danger to life and health from minute, invisible germs, and to exerting all our skill in order to destroy them, that the knowledge of the existence of large and beautiful trees in our midst which can, and do, cause terrible disease and suffering by their mere presence, comes as a shock, and produces a peculiar sense of insecurity greater even than that excited by unseen micro-organisms. For the trees of which I am about to speak are cultivated in our gardens, trained up against the walls of our houses with loving care, and admired for the beautiful autumn tints of their leaves. Yet it is now certain that they are the cause in many persons of most terrible suffering and illness. I am glad to be able to warn my readers in regard to these plants, and I shall be very much interested to hear whether the information which I am about to give proves to be of value in any particular case.

A married couple, friends of my own, went to live, about fourteen years ago, in a newly built, detached house, standing in its own garden, in the neighbourhood of an English city. After they had been there two years the lady developed a very painful eruption or eczema on the face, which, in the course of a few weeks, caused the eyes, nose, and lips to swell to an extraordinary degree, accompanied by the formation of blisters and breaking of the skin. The affection spread to the body, and caused constant pain and corresponding prostration. Her medical attendants were unable either to cure or to account for her condition. After some months she left home, and entirely recovered. But every year the same distressing and disfiguring illness attacked her (commencing in the month of June), and disappeared as soon as she left her house, only to return when she came back to it. The doctors spoke of her affliction as a mysterious form of erysipelas, and even suggested blood-poisoning as the cause. For long periods she was so ill and in so much pain that she was unable to see her friends, and her life was at times in danger.

Two years ago a weekly newspaper published an account, written by a correspondent, of an illness from which he had suffered—exactly agreeing with that which had for so many years tortured my friend’s wife. This writer stated that he had ascertained that the disease was due to the action of a poison given off by a creeper which grew on the walls of his house. He had supposed this plant to be a Virginian creeper; but he had discovered that it was in reality the Californian poison-vine called by botanists Rhus toxicodendron. The terribly poisonous nature of this plant is well-known to the people of the United States. It is one of the sumach trees, of which other poisonous kinds are known, whilst more than one species is used (especially in Japan) for preparing a resinous varnish which is used in the manufacture of “lacquered” articles. The writer in the weekly paper stated that he had cut down and burnt the poison-vine which grew on the walls of his house, and that his sufferings had ceased. My friend happened to read this account, and immediately examined his own house. He found a creeper resembling a Virginian creeper, but having three leaflets or divisions of the leaf instead of five, growing around his drawing-room window, and actually spreading its branches and leaves over the window of his wife’s bedroom. He sent specimens of the creeper to Kew, where it was at once identified as the Rhus toxicodendron or American poison-vine or poison-ivy. He caused the plant to be removed and burnt, and, except for a slight attack in July, due no doubt to fragments of the leaves still carried about in the form of dust, his wife has recovered her health.

I have looked into this matter with care, and I find that (presumably in ignorance) nurserymen in England have sold specimens of the poison-vine for planting as creepers, under the name Ampelopsis Hoggii. The smaller-leaved Virginian creeper, with self-attaching tendrils, is known as Ampelopsis Veitchii, and is, like the larger Virginian creeper (A. quinquefoliata), quite harmless. The poison-vine is not an Ampelopsis at all, not even one of the Vitaceæ or vine family, as that genus is. It is a Sumach or Rhus, and belongs to a distinct family, the Terebinthaceæ. It has a three-split leaf, not five leaflets, as has the large Virginian creeper, nor a small three-pointed leaf, as has the Ampelopsis Veitchii. The Veitchii frequently has the leaf also split into three leaflets, but the stalk of the middle leaflet is not relatively so long as it is in the poison-vine. The differences and resemblances in the leaves of these plants are shown in the accompanying illustration ([Fig. 14]), which has been prepared from actual specimens for this book.

The people of the United States are on their guard against this plant, knowing its terrible properties. Sir William Thiselton Dyer, formerly director of Kew Gardens, tells me that specimens of the “American poison-vine” are grown in the garden at Kew, and that he has been present when American visitors (ladies) literally screamed with horror on seeing it, and ran from it as from a mad dog. Several cases are on record of the mysterious poisoning produced by this plant in England; but it is strangely unfamiliar to medical practitioners—indeed, practically unknown to them, although I have ascertained that many English people, especially ladies, have been victims for some years to its unsuspected influence.

At the University of Harvard, in Cambridge, Massachusetts, they have made quite recently a thorough examination of the poison-vine in the laboratory, with the following results: The poison is an oil—a fixed oil, not a volatile one, as we might have imagined from its mysterious action at a distance. The oil exists in all parts of the plant, even in the fine hairs and cuticle of the leaf. It can be extracted by means of ether, and is one of the most virulent irritants known, having a very curious penetrating and persistent action, and producing violent pain and destruction of tissue when placed on the skin in quantity so minute (one-thousandth of a milligram in two drops of olive oil) as to be beyond the terms of everyday language. It seems to be usually brought to the eyes, nose, lips, and skin of the face and body by the fingers which have touched a leaf or fragments of a leaf in powder. The dead leaf in winter still retains the oil, and minute dust-like particles can carry it. The treatment for it is washing with soap, oil, and ether at an early stage of the attack—especial care being taken to free the fingers from any minute traces of the oil adhering to them.

Fig. 14.—Drawings, about half the natural size, of the leaves of the common quinquefoliate Virginian creeper (1 and 2), of the adherent “Ampelopsis Veitchii” (3 and 4), and of the poison-vine, Rhus toxicodendron (5 and 6). From specimens in the Botanical Department of the Natural History Museum. Note especially the greater length of the stalk of the central leaflet in the poison-vine. Note also that the common Virginian creeper has sometimes only three leaflets (2) instead of five, and that “Veitchii” has either three leaflets, as in 3, or has the leaflets united into one three-pointed leaf, as in 4.

[Transcriber’s Note: The original image is approximately 5½ inches (14cm) high and 3½ inches (8.5cm) wide in total.]

The poison of the poison-vine only acts upon a limited number of individuals, many people being perfectly immune. At the same time, the effect upon susceptible people appears to be enhanced with every fresh attack; even after the total removal of the poison-vine and its dust from proximity to a susceptible person, he or she is apt for some time—owing to the retention of some trace of the oil in the skin or clothes—to have slight attacks. According to a writer who two years ago gave in the Spectator an account of his own case, the first symptom of an attack is almost invariably a redness and irritation of the eyelids, accompanied by shivering. In a few hours the eyelids are closed, the features unrecognisable, and the skin covered with little blisters. Then the lips swell enormously, the glands of the neck also. In four days the arms and hands are reached, each finger appearing as if terribly scalded and requiring separate bandaging. Then sometimes the lower limbs are involved. After ten days the attack passes off, leaving the patient in a pitiable state of weakness to grow a new skin and recover from other painful results of the poisoning. But no immunity is conferred by an attack; the unhappy victim (who is ignorant of the cause of his sufferings) may, and frequently does, get a new dose of the poison as soon as he has recovered, and the whole course of the illness has again to be passed through. If this account should fall into the hands of any one who is being unwittingly poisoned by the American poison-vine, and may therefore be saved by what I have written from further suffering, I shall be greatly pleased.

There are very few plants which have a power of diffusing poison around them; usually it is necessary to touch or to eat portions of a plant before it can exert any poisonous effect. The eighteenth-century story of the upas-tree of Java, which was fabled to fill a whole valley with its poisonous emanation, and to cause the death of animals and birds at a distance of fifteen miles, is now known to be a romantic invention. The tree in question is merely one having a poisonous juice which was extracted and used by the wilder races of Java as an arrow poison. It is stated that one of the stinging-nettles of tropical India has such virulent poison and such an abundance of it in the hairs on its surface, that explorers have been injured by merely approaching it, the detached hairs probably floating in the air and getting into the eyes, nose, and throat of any one coming near it. The poison of the poisonous stings of both plants and of animals has been to some extent examined of late years. It is a curious fact that there are proportionately few plants which sting as compared with the number and variety of animals which do so. On the other hand, there are an enormous number of plants which are poisonous to man when eaten by him, but there are very few animals which are so.

It will be of interest to my readers to know that I received, in consequence of the publication of the foregoing account of the “Poison-vine” or “Poison-ivy,” more than fifty letters and boxes containing leaves. At Kew Gardens nearly a hundred applications were made with a request for the identification of leaves. The proportion of cases in which leaves of true poison-ivy (Rhus toxicodendron) were sent to me seems to be the same as that which they observed at Kew—only two samples of the leaves sent to me were those of the true poison-ivy. Hence we may conclude that the plant has not been very largely introduced in this country, and probably there are not many hundred cases existing in England of the painful malady which it can, in certain people, produce. I have, however, received information of several instances of this poisoning from different parts of the country, which are either now under treatment or have been cured, and in some cases the poison-ivy has been discovered as the cause, owing to the description which I published. It is certainly true that the illness caused by this plant only attacks a small proportion of those who handle it, and it is possible that the plant is more virulent at some seasons and in some soils than in others. In the United States, even in the neighbourhood of New York, it is a real danger, and is recognised as such, but as appears from a letter which I quote below, the reason of the dread which the “poison-ivy” excites in the States depends on the fact that it is not there a mere garden plant, but grows wild in great abundance in the woodlands frequented by holiday-makers and lovers of natural forest and lakeside wilderness. The poisonous nature of the allied species of Rhus used for the manufacture of “lacquer” or varnish is recognised by the Japanese and others who prepare this product and have to handle the plant—they wear gloves to protect the hands.

As showing what kind of trouble the “poison-ivy” and “poison-oak” (another kind of Rhus or Sumach) give in the United States, I will quote a letter I have received from an American lady well known in London society. She says: “I have known, suffered, and struggled against the poison-ivy in America from my earliest years, when my poor mother lay for days with blinded and swollen eyes, having gathered it inadvertently. The ‘poison-ivy,’ as we call it, is a curse to country life, outside the purely artificial and cultivated gardens, and even there it creeps in insidiously.” She describes a beautiful farm property on Lake Champlain, on the Canadian border, where she and her family would spend many weeks in summer in order to enjoy the delights of complete seclusion in wild, unspoilt country: “The one and only drawback to the place was,” she writes, “the inexhaustible quantity of poison-ivy. Our first duty had been to teach my two daughters and their governess how to distinguish and avoid contact with it. The one and only rule was that the poison-ivy has the clusters of three leaflets (the middle leaflet with a longer stalk, E.R.L.), whereas the woodbine (not the English woodbine, which is a convolvulus, E.R.L.), or, as you call it, ‘Virginian creeper,’ has five leaflets in a cluster. Every path which we used frequently and necessarily, such as the path to the boat-house, and to the cove where the bathing-house stood, we kept cleared of the Rhus for a sufficient width, but in the woods eternal vigilance was the price of safety. To uproot and burn is the only way to destroy it, but, of course, that involves danger to the one who does the work, because contact with the spade used, and with the garments which touched the ivy, might communicate the poison. The farmer and the countryfolk about declared that the fumes from the burning plant could and did poison those who breathed them. We used to turn a flock of sheep into the most used parts. They prefer the poison-ivy to grass, and greedily eat down every leaf within reach in hedge or path. But that, of course, was a mere temporary safety, as the plant is most tenacious of life. I personally had a most grievous experience one summer. I can only suppose that my dress, though very short for wood and hill walking, brushed over the poisonous plant, and then, when I undressed, came into contact with my skin. Both legs became covered with the eruption, eventually developing pustules, and the agony of itching, burning, and smarting was indescribable. The first remedy applied is usually a frequent use of baths of some alkali, generally common soda. With me it was altogether inadequate, and the doctor carefully covered the affected parts with a thick layer of bismuth, and bandaged them, so as to exclude all air. But it took weeks to cure me. A very serious result in many cases is that there is a recurrence of the itching for several years.”

[XII]
POISONS AND STINGS OF PLANTS AND ANIMALS

To give an account of poisonous plants would require a whole volume. Among plants of every degree and kind are many which produce special chemical substances which are more or less poisonous, and yet often of the greatest value to man when used in appropriate doses, though injurious and even deadly if swallowed in large quantity. Plants are laboratories which build up in a thousand varieties wonderful chemical bodies, some crystalline, some oils, some volatile (as perfumes and aromatic substances), some brilliantly coloured (used as dyes), some pungent, some antiseptic, some of the greatest value as food, and some even digestive, similar to or identical with those formed in the stomach of an animal.

Man, the chemist, every year is learning how to produce in his own laboratories, from coal and wood refuse, many of these bodies, so as to become to an ever-increasing extent independent of the somewhat capricious and costly services of the chemists supplied by nature—the plants. In a recent exhibition there was a case showing on one side the various essential oils used to make up a flask of eau-de-Cologne, and specimens of the plants, flowers, leaves, and fruits from which they are distilled. On the other side of the case was a series of bottles showing the steps in the process by which the modern chemist manufactures from coal-tar and coker-butter the same bodies which give value to the vegetable extracts, and there was finally a bottle of what is called “synthetic eau-de-Cologne”—that is, eau-de-Cologne put together from the products manufactured by the human, instead of the vegetable, chemist.

Whilst man has learnt to avoid swallowing poisonous plants, although occasionally blundering over pretty-looking berries and deceptive mushrooms, he has had little to fear in that way from animals. To a small degree this is due to the fact that only parts of animals are eaten by man, and those very generally are cooked before being eaten, the heating often sufficing to destroy substances present in flesh, fish, and fowl which would be poisonous if taken raw. But, as a matter of fact, animals do not generally protect themselves from being eaten, as plants largely do, by developing nasty or poisonous substances in their flesh, though some do. They fight rather by claws, teeth, and poison glands therewith connected, or else escape by extra quick locomotion, a method not possible to plants. Many insects (butterflies, beetles, and bugs), however, produce nasty aromatic substances which cause animals like birds and lizards to reject them as food. The toad and the salamander both produce a very deadly poison in their damp, soft skins, which causes any animal to drop them from its mouth, and to regret “bitterly” the attempt to swallow them. The frog has no such poison in its skin, but can jump out of harm’s way. The strong yellow and black marking of the European salamander is what is called a “warning” coloration, just as is the yellow and black outfit of the poisonous wasp. Animals learn to leave the yellow and black livery untouched, and the creatures so marked escape the injury which would be caused them by tentative bites.

There is a curious variation as to susceptibility on the part of man to poison in the flesh of fishes and shell-fishes when taken by him as food. The word “idiosyncrasy” is applied to such individual susceptibility, and is, of course, applicable to the susceptibility shown by some persons to the poison of the American poison-vine, described in the last article, and of others to acute inflammation from the dust of hayfields. Some persons cannot eat lobster, crab, or oysters or mussels without being poisoned in a varying degree by certain substances present in those “shell-fish” even when cooked. Often a “rash” is caused on the skin, and colic. Others, again, cannot eat any fish of any kind without being poisoned in a similar way, or possibly are only liable to be poisoned by grey mullet or by mackerel. The most curious cases of this individual variability are found in the rash and fever caused by the vegetable drug quinine in rare instances, and the violent excitement produced in some persons by the usually soporific laudanum. All such cases have very great interest as showing us what a small difference separates an agreeable flavour or a valuable medicine from a rank poison, and how readily the chemical susceptibility of a complex organism like man may vary between toleration and deathly response, without any concomitant indication of such difference being apparent (in our present state of knowledge), in two individuals, to one of whom that is poison which to the other is meat. They also furnish a parallel to that marvellous conversion of “toxin” into “anti-toxin,” in consequence of which the blood of an animal injected with small, increasing doses of deadly snake poison or diphtheria poison becomes an antidote to the same poison taken into the blood of an unprepared animal.

There is, over and above these special cases of fish foods which are tolerated by some and are poison to others, a whole series of fishes which cannot be eaten by any one without serious poisoning being the result, even when the fish are carefully cooked. Happily, these fishes are rarely, if ever, caught on our own coasts. They produce, when even small bits are eaten, violent irritation of the intestine, and death, the symptoms resembling in many respects those of cholera. The curious bright-coloured, beaked fish of tropical seas and coral reefs, with two or four large front teeth and spherical spine-covered bodies, and the trigger fish of the same regions, are the chief of these poisonous fish. But there is a true anchovy on the coast of Japan, and a small herring in the West Indies, and a goby on the Indian coast (Pondicherry), all of which are deadly poison even when cooked; and there are many others. So one has to be careful about fish-eating in the remoter parts of the world. The poisons of these fish with poisonous flesh have not been carefully studied, but they seem to resemble chemically the poisons produced by certain putrefactive microbes.

Let us now revert to the more special subject of poisonous stings. Every one knows that although it is unpleasant to be pricked by the little spines on the leaf of a thistle, it is not the same unpleasantness as being “stung” by a nettle. There is no poison in the thistle. The hairs which beset the leaves of the common nettle are firm, but brittle and hollow; they break off in the skin, and a poison exudes from their interior. Under the microscope—and it is quite easy to examine it with a high power—the hollow nettle hair is seen to be partly occupied by living protoplasm—a transparent, viscid substance which shows an active streaming movement, and has embedded in it a dense kernel or nucleus (see [Fig. 15 bis]). It is, in fact, a living “cell,” or life unit. The space in the cell not occupied by protoplasm is filled with clear liquid, which contains the poison. This has been examined chemically by using a large quantity of nettle hairs, and is found to contain formic acid—the same irritating acid which is secreted by ants when they sting, whence its name. But later observations show that the juice of the nettle hair contains also a special poison in minute quantities, an albuminous substance, which resembles that contained in the poison-sacs at the base of the teeth of snakes.

In tropical regions there are nettles far more powerful than that of our own country. The one called Urtica stimulans, which is found in Java, and that called Laportea crenulata, found in Hindostan, when bruised emit an effluvium which poisonously affects the eyes and mouth, and if handled produce convulsions and serious swelling and pain in the arms, which may last for three or four weeks, and in some cases cause death. They are not unknown in the hothouses of our botanical gardens, and young gardeners are sometimes badly stung by them. There are other plants provided with poisonous stinging hairs besides the true nettles or Urticaceæ, though they are not numerous. The American plants called Loasa sting badly, so do some of the Spurges (Euphorbiaceæ), and some Hydrophylleæ.

The Chinese primrose (Primula obconica), lately introduced into greenhouses, has been found to be almost as injurious as the poison-vine. Its effects, of course, are limited to a much smaller group of sufferers. And it is worth while, in connection with poisoning by primula and the poisoning by Rhus toxicodendron of only certain individuals predisposed to its influence, to point out that the malady known as hay fever seems to be similar in its character to these vegetable poisonings. It is, of course, well known that only certain individuals are liable to the more violent and serious form of hay fever. It is not at all improbable that this irritation of the air passages, often attributed to the mechanical action of the pollen of grass and other plants—really is due to minute quantities of a poison like that of the poison-vine, present in the pollen of some hay plant yet to be suspected, tried, and convicted.[2]

With regard to a poisonous action at a distance being possibly exerted by plants, we must not overlook the effects of some perfumes discharged into the air by flowers. Primarily such perfumes appear to serve the flowers by attracting to them special insects, by whose movements and search for honey in the flowers the pollen of one is conveyed to another and fertilisation effected. Human beings are sometimes injuriously affected by the heavy perfume given out by lilies and other flowers, headache and even fainting being the result. No instance is known of serious injury or death resulting in the regions where they grow from the overpowering perfume of such flowers. But that admirable story-teller, Mr. H. G. Wells, has made a legitimate use of scientific possibilities in imagining the existence of a rare tropical orchid which attracts large animals to it by its wonderful odour. The effects of the perfume are narcotising; the animal, having sniffed at the orchid, drops insensible at the foot of the tree trunk on which the orchid grows. Then the orchid rapidly, with animal-like celerity, sends forth those smooth green fingers or “suckers,” which you may see clinging to the pots and shelves on which an orchid is growing. As they slowly creep, in their growth, over the poisoned animal, they absorb its life’s blood painlessly and without disturbing the death-slumber of the victim. Mr. Wells supposes a retired civil-servant, with feeble health and a passion for orchids, to have purchased an unknown specimen, which, after some months of nursing, is about to blossom in the little hothouse of his suburban home. He goes quietly and alone one afternoon, when his housekeeper is preparing his tea, to enjoy the first sight and smell of the unknown flower, and is found, some three hours later, lying insensible before the orchid, which is giving out an intoxicating odour, and is looking very vigorous and wicked. A blood-red tint pervades its leaves and stalks, and it has already pushed some of its finger-like shoots round the orchid-lover’s neck and beneath his shirt front. When they are pulled away a few drops of blood flow from the skin where the absorbent shoots had applied themselves. The victim recovers.

When we take a survey of the “stings” and poison-fangs and spurs of animals, we find a much greater abundance and variety of these weapons than in plants. They serve animals not only as a means of defence, but very often for the purpose of attacking and paralysing their prey. We have to distinguish broadly between (a) gut-poisons and (b) wound-poisons. The slimy surface of the skin and the juices of animals are often poisonous if introduced into wounds, but harmless if swallowed, though in the toad and salamander the skin contains a poison which acts on the mouth and stomach. Thus the blood of the eel is poisonous to higher animals if injected beneath the skin, though not poisonous when swallowed. Pasteur found that the saliva of a healthy human baby a few weeks old produced convulsions when injected beneath the skin of a rabbit. The fluid of the mouth in fishes (Muræna), in some lizards (Heloderma), and some warm-blooded quadrupeds, like the skunk, is often poisonous, and is introduced into the wound inflicted by a bite. The elaboration of a sac of the mouth-surface secreting a special quantity of poison to be injected by aid of a grooved tooth, such as we find in poisonous snakes, is only a mechanical improvement of this more general condition. The same general poisonous quality is found in the slime of the skins of fishes which have spines by means of which poisonous wounds are inflicted (sting-rays). And here, too, an elaboration is effected in some fishes in which a sac is provided for the accumulation of the poison, and a specially grooved spine, to convey the poison into the wound inflicted by it. A common fish on our coasts, the weever (probably the same word as viper), is provided with grooved, stinging spines, but no special poison-sac. Some of the poison-carrying spines support the front portion of the dorsal fin, which is of a deep black colour, a striking instance of the warning coloration which poisonous animals often possess.

The poison introduced into wounds by the spines or fangs of animals is essentially similar to that of nettle hairs; it has the effect of paralysing and of producing convulsions. It is a remarkable fact that formic acid often in insects accompanies the paralysing poison—as it does in the nettle—and produces intense pain and irritation, which the more dangerous nerve-poison does not. Immunity to a given wound-poison may be produced by the injection of doses of it, at first excessively minute, but gradually increased in quantity. A remedial “anti-toxin” is thus prepared from the blood of immunised animals, which is used as a cure or as a protection by injecting it into other animals exposed to bites or wounds conveying the particular poison by the use of which the anti-toxin was produced. Bee-keepers who have often been stung become in many cases immune, and do not suffer from bee-sting. Men who in France pursue a business as viper-catchers, are said to become immune to viper’s poison in the same way. Snakes and scorpions are but little, if at all, affected by their own poison when it is injected into them. This appears to be due to the fact that the poison-producing animal is always absorbing into its blood very minute doses of the poison which it has elaborated and stored up in its poison-sac connected with the poison-gland. This small quantity of poison continually absorbed is continually converted into an anti-toxin—just as happens when a horse is treated with doses of snake-poison to prepare the remedial anti-toxin for use in cases of snake-bite, or with diphtheria-poison in order to prepare the diphtheria anti-toxin now so largely used. The anti-toxin is a substance very closely similar in chemical constitution to the toxin by the conversion of which it is formed in the blood. Its action on the toxin (or essential poisonous substance of the venom) appears to be a very delicate and slight chemical disturbance of the constitution of that chemical body. Yet it is enough to cause the injurious quality of the toxin to be suddenly and completely abrogated, although from the point of view of chemical composition it is only, as it were, shaken or given a twist! Such great practical differences in the action on living creatures of chemical bodies having themselves so subtle a difference of chemical structure as to almost defy our powers of detection, are now well known.

Fig. 15.—Drawing from life of the desert scorpion (Buthus australis, Lin.), from Biskra, N. Africa, of the natural size. (From Lankester, Journ. Linn. Soc. Zool., vol. xvi. 1881.)

[Transcriber’s Note: The original image is approximately 2 inches (5cm) high and 3 inches (7.5cm) wide.]

I made some experiments a few years ago on the poison of scorpions, which were published by the Linnæan Society. I obtained live scorpions—a beautiful citron-coloured kind, of large size—from Biskra, in Algeria ([Fig. 15]). The poison-gland and sac are double, and contained in the last joint of the tail, which is swollen, and ends in a splendid curved spine or sting. The scorpion carries its tail raised in a graceful curve over its back, and strikes with the sting by a powerful forward stroke. One can seize the tail by the last joint but one, and thus safely hold the animal, and see the poison exude in drops from the perforated sting. I found that if I pressed the sting thus held into the scorpion’s own body, or into that of another scorpion, no harm resulted to the wounded animal, although plenty of the poison entered the little wound made by the sting. A large cockroach or a mouse similarly wounded by the sting was paralysed, and died in a few minutes. It is a custom in countries where scorpions abound, and are troublesome, and even dangerous to human life, for the natives to make a circle of red-hot charcoal, and to place a large scorpion in the centre of the enclosed area. The scorpion, it is stated, runs round inside the circle, and, finding that escape is impossible, deliberately drives its sting into its back, and so commits suicide. My experiments showed that the scorpion could not kill itself in this way, as its poison does not act on itself. Moreover, it has been shown by Professor Bourne, of Madras, that although scorpions constantly fight with one another, they never attempt to use their stings in these battles, but only their powerful, lobster-like claws. The stings would be useless, and are reserved for their attacks on animals susceptible to the poison. I also found the ground for the belief that the scorpion kills itself when enclosed in a fiery circle. Incredible as it may appear in regard to such denizens of the hot regions of the earth, both the desert scorpion and the large dark-green Indian scorpions actually faint and become motionless and insensible when exposed for a few minutes to a temperature a little above that of the human body. This was carefully ascertained by using an incubator and a thermometer. The scorpion in the fiery circle lashes about with its sting, and then suddenly faints owing to the heat. If removed from the heat it recovers completely; but, of course, when it is supposed to have committed suicide, no one takes the trouble to remove it. I made, several times, the actual experiment of placing a large active scorpion within a ring-like wall, a foot in diameter, formed by live coals. The scorpion never stung itself. On one occasion it walked out over the coals, and on other occasions, after lashing its tail and running about, fainted, and became motionless.

Jelly-fishes are often called “sea-nettles,” because of the microscopic poison-bearing threads which they discharge from their skin. These are used to paralyse their prey, and, in a few kinds only, are sufficiently powerful to cause a “stinging” effect when they come into contact with a bather’s skin. Sea-anemones are also armed with these minute threads, and their poison has been extracted and studied. The spines of star-fishes and sea-urchins have a very deadly poison associated with them, which has recently been examined. Among insects we have the bees, wasps, and ants, with their terminal stings; caterpillars, with poisonous hairs; gnats, with poisonous mouth glands. Residents in mosquito-infested countries become “immune” to the poison of gnat-bite, but not to the deadly germs of malaria and yellow fever carried by the gnats. The centipedes have powerful jaws, provided with poison-sacs; the spiders have stabbing claws, fitted with poison-glands. Shell-fish, such as crabs and lobsters, do not possess stings or poison-sacs, but some of the whelk-like sea-snails have poison-glands, which secrete a fluid deadly to other shell-fish. We have already spoken of the poison-spines of fishes; among reptiles it is only some of the snakes which are poisonous, and are known to have poison-glands connected with grooved fangs. Only one kind of lizard—the Heloderm of North America, already mentioned—has poison-glands in its mouth, but it has no special poison-fangs, only small teeth. There is a most persistent and curious popular error to the effect that the rapidly moving bifid tongue of snakes and lizards is a “sting.” It is really quite innocuous. No sting is known among birds, although some have fighting “spurs” on the leg, and “claws” on the wing.

Only the lowest of the mammals or warm-blooded hairy quadrupeds—namely, the Australian duck-mole (Ornithorhynchus) and the spiny ant-eater (Echidna)—have poison-glands and related “spurs,” or stings. They have on the hind-leg a “spur” of great size and strength, which is perforated and connected with a gland which produces a poisonous milky fluid. Recent observations, however, as to the poisonous character of this fluid are wanting. Many mammals have large sac-like glands, which open by definite apertures, in some cases between the toes, in others upon the legs, at the side or back of the head (the elephant), in the middle of the back or about the tail. The fluid secreted by these glands is not poisonous nor acrid, but odoriferous, and seems to serve to attract the individuals of a species to one another. They resemble in structure and often in position the poison-glands of the spurs of the duck-mole and spiny ant-eater.

Many insects produce a good deal of irritation, and even dangerous sores, by biting and burrowing in the human skin, without secreting any active poison. Often they introduce microscopic germs of disease in this way from one animal to another, as, for instance, do gnats, tsetze-flies, and horse-flies, and as do some small kinds of tics. The bites of the flea, of midges, gnats, and bugs are comparatively harmless unless germs of disease are introduced by them, an occurrence which, though exceptional, is yet a great and terrible danger. We now know that it is in this way, and this way only, that malaria or ague, yellow fever, plague, sleeping-sickness, and some other diseases are carried from infected to healthy men. Various diseases of horses and cattle are propagated in the same way. The mere bites of insects may be treated with an application of carbolic acid dissolved in camphor. The pain caused by the acid stings of bees, wasps, ants, and nettles can be alleviated by dabbing the wound with weak ammonia (hartshorn). Insects which bury themselves in the skin, such as the jigger-flea of the West Indies and tropical Africa, should be dug out with a needle or fine blade. The minute creature, like a cheese-mite, which burrows and breeds in the skin of man and causes the affliction known as the itch must be poisoned by sulphurous acid—a result achieved by rubbing the skin freely with sulphur ointment on two or three successive days. A serious pest in the summer in many parts of England is a little animal known as the harvest-man. These are the young of a small red spider-like creature, called Trombidium. They get on to the feet of persons walking in the grass, and crawl up the legs and burrow into the tender skin. Benzine will keep them away if applied to the ankles or stockings when they are about, and will also destroy them once they have effected a lodgment.

Fig. 15 bis.—A. Highly magnified drawing of a stinging hair of the common nettle. The hair is seen to be a single cell or capsule of large size, tapering to its extremity, but ending in a little knob. The hard case e is filled with liquid a, and is lined with slimy granular “protoplasm” b, which extends in threads across the cavity to the “nucleus” c. The ordinary small cells of the nettle leaf are marked d. B shows the knobbed end of the stinging hair, and the way in which, owing to the thinness of its walls, it breaks off along the line xy when pressed, leaving a sharp projecting edge, which penetrates the skin of an animal, whilst the protoplasm p, distended with poisonous liquid, is shown in C, issuing from the broken end. It would escape in this way when the sharp, freshly broken end had penetrated some animal’s skin.

FOOTNOTES:

[2] Since the above was written, I have seen the account by an American physician—in a recently issued volume of Osler’s Treatise on Medicine—of his recent discovery of the grass which produces in its pollen the poison of hay fever, and of the preparation by him of an anti-toxin which appears to give relief to those who suffer from hay fever.