Chapter XIV: Appendix: A List of Sources (6)

The session begins with a brief off-hand discussion of the general characteristics and affinities of the group of arthropoda, of which the crawfish is a member. Then, perhaps, the professor calls the students about him and gives a demonstration of the curious phenomena of hypnotism as applied to the crawfish, through which a living specimen, when held for a few moments in a constrained attitude, will pass into a rigid "trance," and remain standing on its head or in any other grotesque position for an indefinite period, until aroused by a blow on the table or other shock. Such are some of the little asides, so to speak, with which the virile teacher enlivens his subject and gives it broad, human interest. Now each student turns to his microscope and his individual dissection, and the professor passes from one investigator to another with comment, suggestion, and criticism; answering questions, propounding anatomical enigmas for solution--enlivening, vivifying, inspiring the entire situation.

As the work proceeds, Professor Haeckel now and again calls the attention of the entire class to some particular phase of the subject just passing under their individual observation, and in the most informal of talks, illustrated on blackboard and chart, clears up any lurking mysteries of the anatomy, or enlivens the subject with an incursion into physiology, embryology, or comparative morphology of the parts under observation. Thus by the close of the session the student has something far more than a mere first-hand knowledge of the anatomy of the crawfish--though that in itself were much. He has an insight also into a half-dozen allied subjects. He has learned to look on the crawfish as a link in a living chain--a creature with physiological, psychological, ontological affinities that give it a human interest not hitherto suspected by the novitiate. And when the entire series of Sunday-morning "services" has been carried through, one order after another of the animal kingdom being similarly made tribute, the favored student has gone far towards the goal of a truly philosophical zoology, as different from the old-time dry-bones anatomy as the living crawfish is different from the dead shell which it casts off in its annual moulting time.

THE NEW ZOOLOGY

What, then, is the essence of this "philosophical zoology" of which Haeckel is the greatest living exponent and teacher and of which his pupils are among the most active promoters? In other words, what is the real status, and the import and meaning, the _raison d'être_, if you will, of the science of zoology to-day?

To clear the ground for an answer to that question, one must glance backward, say half a century, and note the status of the zoology of that day, that one may see how utterly the point of view has changed since then; what a different thing zoology has become in our generation from what it was, for example, when young Haeckel was a student at Jena back in the fifties. At that time the science of zoology was a conglomeration of facts and observations about living things, grouped about a set of specious and sadly mistaken principles. It was held, following Cuvier, that the beings of the animal kingdom had been created in accordance with five preconceived types: the vertebrate, with a spinal column; the articulate, with jointed body and members, as represented by the familiar crustaceans and insects; the mollusk, of which the oyster and the snail are familiar examples; the radiate, with its axially disposed members, as seen in the starfish; and the low, almost formless protozoon, most of whose representatives are of microscopic size. Each of these so-called classes was supposed to stand utterly isolated from the others, as the embodiment of a distinct and tangible idea. So, too, of the lesser groups or orders within each class, and of the still more subordinate groups, named technically families, genera; and, finally, the individual species. That the grouping of species into these groups was more or less arbitrary was of course to some extent understood, yet it was not questioned by the general run of zoologists that a genus, for example, represented a truly natural group of species that had been created as variations upon one idea or plan, much as an architect might make a variety of houses, no one exactly like any other, yet all conforming to a particular type or genus of architecture--for example, the Gothic or the Romanesque. That each of the groups defined by the classifiers had such status as this was the stock doctrine of zoology, as also that the individual species making up the groups, and hence the groups themselves, maintained their individual identity absolutely unaltered from the moment of their creation, throughout all successive generations, to the end of their racial existence.

Such being the fundamental conception of zoology, it remained only for the investigator to study each individual species with an eye to its affinities with other species, that each might be assigned by a scientific classification to the particular place in the original scheme of creation which it was destined to occupy. Once such affinities had been correctly determined and interpreted for all species, the zoological classification would be complete for all time. A survey of the completed schedule of classification would then show at a glance the details of the preconceived system in accordance with which the members of the animal kingdom were created, and zoology would be a "finished" science.

In the application of this relatively simple scheme, to be sure, no end of difficulties were encountered. Each higher animal is composed of so many members and organs, of such diverse variations, that naturalists could never agree among themselves as to just where a balance of affinities between resemblances and differences should be struck; whether, for example, a given species varied so much from the type species of a genus--say the genus Gothic house--as to belong properly to an independent genus--say Romanesque house; or whether, on the other hand, its divergencies were still so outweighed by its resemblances as to permit of its retention as an aberrant member of genus number one. Perpetual quibbling over these matters was quite the order of the day, no two authorities ever agreeing as to details of classification. The sole point of agreement was that preconceived types were in question--if only the zoologists could ever determine just what these types were. Meantime, the student who supposed classifications to be matters of moment, and who laboriously learned to label the animals and birds of his acquaintance with an authoritative Latin name, was perpetually obliged to unlearn what he had acquired, as a new classifier brought new resources of hair-splitting pursuit of a supposed type or ideal to bear on the subject. Where, for example, our great ornithologists of the early part of the century, such as Wilson and Audubon, had classed all our numerous hawks in a genus falco, later students split the group up into numerous genera--just how many it is impossible to say, as no two authorities agreed on that point. Wilson, could he have come back a generation after his death, would have found himself quite at a loss to converse with his successors about the birds he knew and loved so well, using their technical names--though the birds themselves had not changed.

Notwithstanding all the differences of opinion about matters of detail, however, there was, nevertheless, substantial agreement about the broader outlines of classifications, and it might fairly enough have been hoped that some day, when longer study had led to finer discrimination, the mysteries of all the types of creation would be fathomed. But then, while this hope still seemed far enough from realization, Charles Darwin came forward with his revolutionizing doctrine--and the whole time-honored myth of "types" of creation vanished in thin air. It became clear that the zoologists had been attempting a task utterly Sisyphean. They had sought to establish "natural groups" where groups do not exist in nature. They were eagerly peering after an ideal that had no existence outside their imagination. Their barriers of words could not be made to conform to barriers of nature, because in nature there are no barriers.

What, then, was to be done? Should the whole fabric of classification be abandoned? Clearly not, since there can be no science without classification of facts about labelled groupings, however arbitrary. Classifications then must be retained, perfected; only in future it must be remembered that any classification must be more or less arbitrary, and in a sense false; that it is at best only a verbal convenience, not the embodiment of a final ideal. If, for example, we consider the very "natural" group of birds commonly called hawks, we are quite justified in dividing this group into several genera or minor groups, each composed of several species more like one another than like the members of other groups of species--that is, of other genera. But in so doing we must remember that if we could trace the ancestry of our various species of hawks we should find that in the remote past the differences that now separate the groups had been less and less marked, and originally quite non-existent, all the various species having sprung from a common ancestor. The genera of to-day are cousin-groups, let us say; but the parents of the existing species were of one brood, brothers and sisters. And what applies to the minor groups called genera applies also, going farther into the past, to all larger groups as well, so that in the last analysis, all existing creatures being really the evolved and modified descendants of one primordial type, it may be said that all animate creation is but a single kind. In this broadened view the details of classification ceased to have the importance once ascribed to them, and the quibblings of the classifiers seem amusing rather than serious. Yet the changed point of view left the subject by no means barren of interest. For if the multitudinous creatures of the living world are but diversified twig-lets of a great tree of ascent, spread by branching from a common root, at least it is worth knowing what larger branches each group of twiglets--representing a genus, let us say--has sprung from. In particular, since the topmost twig of the tree is represented by man himself and his nearest relatives, is it of human interest to inquire just what branches and main stems will be come upon in tracing back the lineage of this particular offshoot. This attempt had, perhaps, no vast, vital importance in the utilitarian sense in which these terms are oftenest used, but at least it had human interest. Important or otherwise, it was the task that lay open to zoology, and apparently its only task, so soon as the Darwinian hypothesis had made good its status. The man who first took this task in hand, and who has most persistently and wisely followed it, and hence the man who became the recognized leader in the field of the new zoology, was, as I have already intimated, Professor Haeckel. His hypothetical tree of man's lineage, tracing the ancestry of the human family back to the earliest geological times and the lowest orders of beings, has been familiar now for just a third of a century. It was at first confessedly only a tentative genealogy, with many weak limbs and untraced branches. It was perfected from time to time, as new data came to hand, through studies of paleontology, of embryology, and of comparative anatomy. It will be of interest, then, to inquire just what is its status today and to examine briefly Professor Haeckel's own most recent pronouncement regarding it.

Perhaps it is not worth our while here to go too far down towards the root of the genealogical tree to begin our inquiry. So long as it is admitted that the remote ancestry is grounded in the lowest forms of organisms, it perhaps does not greatly matter to the average reader that there are dark places in the lineage during the period when our ancestor had not yet developed a spinal column--when, in other words, he had not attained the dignity of the lowest fish. Neither, perhaps, need we mourn greatly that the exact branch by which our reptilian or amphibian non-mammalian ancestor became the first and most primitive of mammals is still hidden in unexplored recesses of early strata. The most patrician monarch of to-day would not be greatly disturbed as to just who were his ancestors of the days of the cave-dweller. It is when we come a little nearer home that the question begins to take on its seemingly personal significance. Questions of grandparents and great-grandparents concern the patrician very closely. And so all along, the question that has interested the average casual investigator of the Darwinian theory has been the question as to man's immediate ancestor--the parents and grandparents of our race, so to speak. Hence the linking of the word "monkey" with the phrase "Darwinian theory" in the popular mind; and hence, also, the interpretation of the phrase "missing link" in relation to man's ancestry, as applying only to our ancestor and not to any other of the gaps in the genealogical chain.

What, then, is the present status of Haeckel's genealogical tree regarding man's most direct ancestor? Prom what non-human parent did the human race directly spring? That is a question that has proved itself of lasting, vital human interest. It is a question that long was answered only with an hypothesis, but which Professor Haeckel to-day professes to be able to answer with a decisive and affirmative citation not of theories but of facts. In a word, it is claimed that man's immediate ancestor is now actually upon record, that the much-heralded "missing link" is missing no longer. The principal single document, so to speak, on which this claim is based consists of the now famous skull and thigh-bone which the Dutch surgeon, Dr. Eugene Dubois, discovered in the year 1891 in the tertiary strata of the island of Java. Tertiary strata, it should be explained, had never hitherto yielded any fossils bordering on the human type, but this now famous skeleton was unmistakably akin to the human. The thigh in particular, taken by itself, would have been pronounced by any competent anatomist to be of human origin. Unquestionably the individual who bore it had been accustomed to take an erect attitude in walking. And yet the skull was far inferior in size and shape to that of any existing tribe of man--was, indeed, rather of a simian type, though, on the other hand, of about twice the capacity of any existing ape. In a word, it seemed clear that the creature whose part skeleton had been found by Dr. Dubois was of a type intermediate between the lowest existing man and the highest existing man-apes. It was, in short, the actual prototype of that hypothetical creature which Haeckel, in his genealogical tree, had christened _pithecanthropus_, the ape-man. As such it was christened _Pithecanthropus erectus_, the erect ape-man.

Now the discovery of this remarkable form did not make Professor Haeckel any more certain that some such form had existed than he was thirty years before when he christened a hypothetical subject with the title now taken by a tangible claimant. But, after all, there is something very taking about a prophecy fulfilled, and so the appearance of _Pithecanthropus erectus_ created no small sensation in the zoological world. He was hailed by Haeckel and his followers as the veritable "missing link," and as such gained immediate notoriety. But, on the other hand, a reactionary party at once attacked him with the most bitter animadversions, denouncing him as no true ancestor of man with a bitterness that is hard to understand, considering that the origin of man from _some_ lower form has long ceased to be matter of controversy. "_Pithecanthropus_ is at least half an ape," they cried, with the clear implication of "anything but an ape for an ancestor!"

I confess I have always found it hard to understand just why this peculiar aversion should always be held against the unoffending ape tribe. Why it would not be quite as satisfactory to find one's ancestor in an ape as in the alternative lines of, for example, the cow, or the hippopotamus, or the whale, or the dog has always been a mystery. Yet the fact of this prejudice holds. Probably we dislike the ape because of the very patency of his human affinities. The poor relation is objectionable not so much because he is poor as because he is a relation. So, perhaps, it is not the apeness, so to speak, of the ape that is objectionable, but rather the human-ness. In any event, the aversion has been matter of common notoriety ever since the Darwinian theory became fully accepted; it showed itself now with renewed force against poor _pithecanthropus_. A half-score of objections were launched against him. It is needless to rehearse them now, since they were all met valiantly, and the final verdict saw the new-comer triumphantly ensconced in man's ancestral halls as the oldest sojourner there who has any title to be spoken of as "human." He is only half human, to be sure--a veritable ape-man, as his name implies--but exactly therein lies his altogether unique distinction. He is the embodiment of that "missing link" whose nonappearance had hitherto given so much comfort to the sceptical.

Perhaps some crumbs of comfort may be found by the reactionists in the fact that it is not held by Professor Haeckel, or by any other competent authority, that the link which _pithecanthropus_ supplies welds man directly with any existing man-ape--with gorilla, chimpanzee, or orang. It is held that these highest existing apes are side branches, so to say, of the ancestral tree, who developed, in their several ways, contemporaneously with our direct ancestors, but are not themselves directly of the royal line. The existing ape that has clung closest to the direct ancestral type of our own race, it appears, is the gibbon--a creature far less objectionable in that rôle because of the very paucity of his human characteristics, as revealed to the casual observer. Gibbon-like fossil apes are known, in strata representing a time some millions of years antecedent to the epoch of _pithecanthropus_ even, which are held to be directly of the royal line through which _pithecanthropus_, and the hypothetical _Homo stupidus_, and the known _Homo neanderthalensis_, and, lastly, proud _Homo sapiens_ himself have descended. Thus Professor Haeckel is able to make the affirmation, as he did recently before the International Zoological Congress in Cambridge, that man's line of descent is now clearly traced, from a stage back in the Eocene time when our ancestor was not yet more than half arrived to the ape's estate, down to the time of true human development. "There no longer exists," he says, "a 'missing link.' The phyletic continuity of the primate stem, from the oldest lemurs down to man himself, is an historical fact."

It should, perhaps, be added that the force of this rather startling conclusion rests by no means exclusively upon the finding of _pithecanthropus_ and the other fossils, nor indeed upon any paleontological evidence whatever. These, of course, furnish data of a very tangible and convincing kind; but the evidence in its totality includes also a host of data from the realms of embryology and comparative anatomy--data which, as already suggested, enabled Professor Haeckel to predicate the existence of _pithecanthropus_ long in advance of his actual discovery. Whether the more remote gaps in the chain of man's ancestry will be bridged in a manner similarly in accord with Professor Haeckel's predications, it remains for future discoveries of zoologist and paleontologist to determine. In any event, the recent findings have added an increment of glory to that philosophical zoology of which Professor Haeckel is the greatest living exponent.

This tracing of genealogies is doubtless the most spectacular feature of the new zoology, yet it must be clear that the establishment of lines of evolution is at best merely a preparation for the all-important question, Why have these creatures, man included, evolved at all? That question goes to the heart of the new zoological philosophy. A partial answer was, of course, given by Darwin in his great doctrine of natural selection. But this doctrine, while explaining the preservation of favorable variations, made no attempt to account for the variations themselves. Professor Haeckel's contribution to the subject consisted in the revival of the doctrine of Lamarck, that individual variations, in response to environmental influences, are transmitted to the offspring, and thus furnish the material upon which, applying Darwin's principle, evolution may proceed. This Lamarck-Haeckel doctrine was under a cloud for a recent decade, during the brief passing of the Weismannian myth, but it has now emerged, and stands as the one recognized factor in the origin of those variations whose cumulative preservation through natural selection has resulted in the evolution of organic forms.

But may there not be other factors, as yet unrecognized, that supplement the Lamarckian and Darwinian principles in bringing about this marvellous evolution of beings? That, it would seem, is the most vital question that the philosophical zoology of our generation must hand on to the twentieth century. For today not even Professor Haeckel himself can give it answer.

VII. SOME MEDICAL LABORATORIES AND MEDICAL PROBLEMS

THE PASTEUR INSTITUTE

THE national egotism that characterizes the French mind is not without its compensations. It leads, for example, to the tangible recognition of the merits of the great men of the nation and to the promulgation of their names in many public ways. Thus it would be hard to mention a truly distinguished Frenchman of the older generations whose name has not been given to a street in Paris. Of the men of science thus honored, one recalls off-hand the names of Buffon, Cuvier, Geoffroy Saint-Hilaire, Pinel, Esquirol, Lamarck, Laplace, Lavoisier, Arago, Claude Bernard, Broca--indeed, one could readily extend the list to tiresome dimensions. Moreover, it is a list that is periodically increased by the addition of new names, as occasion offers, for the Parisian authorities never hesitate to rechristen a street or a portion of a street, regardless of former associations.

One of the most recent additions to this roll of fame is the name of Pasteur. The boulevard that bears that famous name is situated in a somewhat out-of-the-way corner of the city, though to reach it one has but to traverse the relatively short course of the Avenue de Breteuil from so central a position as the tomb of Napoleon. The Boulevard Pasteur itself is a not long but very spacious thoroughfare, which will some day be very beautiful, when the character of its environing buildings has somewhat changed and its quadruple rows of trees have had time for development. At present its chief distinction, in the eyes of most observers, would probably be found in the fact that it is the location of the famous _fête forain_ at one of the annually recurring stages of the endless itinerary of that noted function. During the period of this distinction, which falls in the month of May, the boulevard becomes transformed into a veritable Coney Island of merry-go-rounds, shooting-galleries, ginger-bread booths, and clap-trap side-shows, to the endless delight of throngs of pleasure-seekers. There is no sight in all Paris worthier inspection for the foreigner than the Boulevard Pasteur offers at this season, for one gains a deep insight into the psychology of a people through observation of the infantile delight with which the adult population here throws itself into the spirit of amusements which with other nations are for the most part reserved for school-children. Only a race either in childhood or senescence, it would seem, could thus give itself over with undisguised delight to the enchantments of wooden horses, cattle, cats, and pigs; to the catching of wooden fish with hooks; to the shooting at targets that one could almost touch with the gun-muzzle, and to the grave observation of sideshow performances that would excite the risibilities of the most unsophisticated audience that could be found in the Mississippi Valley.

As we move among this light-hearted and lightheaded throng we shall scarcely escape a feeling of good-humored contempt for what seems an inferior race. It will be wholesome, therefore, for us to turn aside from the boulevard into the Rue Dotot, which leads from it near its centre, and walk a few hundred yards away from the pleasure-seekers, where an evidence of a quite different and a no less characteristic phase of the national psychology will be before us. For here, within easy sound of the jangling discords of the organs that keep time for the march of the _cheveaux de bois_, rises up a building that is in a sense the monument of a man who was brother in blood and in sentiment to the revellers we have just left in the boulevard, yet whose career stamped him as one of the greatest men of genius of any race or any time. That man was Louis Pasteur. The building before us is the famous institute that bears his name.

In itself this building is a simple and unimposing structure, yet of pleasing contour. It is as well placed as the surroundings permit, on a grassed terrace, a little back from the street, where a high iron fence guards it and gives it a degree of seclusion. There are other buildings visible in the rear, which, as one learns on entering, are laboratories and the like, where the rabbits and guinea-pigs and dogs that are so essential to the work of the laboratory are kept. On the terrace in front is a bronze statue of a boy struggling with a rabid dog--a reminder of the particular labor of the master-worker which led directly to the foundation of the institution. It will be remembered that it was primarily to give Pasteur a wider opportunity to apply his newly discovered treatment for the prevention of rabies that the subscription was undertaken which led finally to the erection of the buildings before us and brought the Pasteur Institute in its present form into being. Of the other aims and objects of the institution I shall speak more at length in a moment.

I have just said that the building before us is in effect the monument of the great savant. This is true in a somewhat more literal sense than might be supposed, for the body of Pasteur rests in a crypt at its base. The personal labors of the great discoverer were practically ended at the time when the institute was opened in 1888, on which occasion, as will be remembered, the scientific representatives of all nations gathered in Paris to do honor to the greatest Frenchman of his generation. He was spared to the world, however, for seven years more, during which time he fully organized the work of the institution along the lines it has since followed, and was, of course, the animating spirit of all the labors undertaken there by his devoted students and assistants. He is the animating spirit of the institution still, and it is fitting that his body should rest in the worthy mausoleum within the walls of that building whose erection was the tangible culmination of his life labors. The sarcophagus is a shrine within this temple of science which will serve to stimulate generations of workers here to walk worthily in the footsteps of the great founder of the institution. For he must be an unimaginative person indeed who, passing beneath that arch bearing the simple inscription "Ici Repose Pasteur," could descend into the simple but impressive mausoleum and stand beside the massive granite sarcophagus without feeling the same kind of mental uplift which comes from contact with a great and noble personality. The pretentious tomb of Galileo in the nave of Santa Croce at Florence, and the crowded resting-place of Newton and Darwin in Westminster Abbey, have no such impressiveness as this solitary vault where rests the body of Pasteur, isolated in death as the mightier spirits must always be in life.

AIMS AND OBJECTS OF THE PASTEUR INSTITUTE

If one chances to come to the institute in the later hours of the morning he will perhaps be surprised to find a motley company of men, women, and children, apparently of many nationalities and from varied walks of life, gathered about one of the entrances or sauntering near by. These are the most direct beneficiaries of the institution, the unfortunate victims of the bites of rabid dogs, who have come here to take the treatment which alone can give them immunity from the terrible consequences of that mishap. Rabies, or hydrophobia as it is more commonly termed with us, is well known to be an absolutely fatal malady, there being no case on record of recovery from the disease once fully established. Even the treatment which Pasteur developed and which is here carried out cannot avail to save the victim in whom the active symptoms of the malady are actually present. But, fortunately, the disease is peculiarly slow in its onset, sometimes not manifesting itself for weeks or months after the inoculation; and this delay, which formerly was to the patient a period of fearful doubt and anxiety, now suffices, happily, for the application of the protective inoculations which enable the person otherwise doomed to resist the poison and go unscathed. Thus it is that the persons who gather here each day to the number of fifty, or even one hundred, have the appearance of and the feelings of average health, though a large proportion of them bear in their systems, on arrival, the germs of a disease that would bring them speedily to a terrible end were it not that the genius of Pasteur had found a way to give them immunity. The number of persons who have been given the anti-rabic treatment here is more than twenty-five thousand. To have given safety to such an army of unfortunates is, indeed, enough merit for any single institution; but it must not be supposed that this record is by any manner of means the full measure of the benefits which the Institut Pasteur has conferred upon humanity. In point of fact, the preparation and use of the anti-rabic serum is only one of many aims of the institution, whose full scope is as wide as the entire domain of contagious diseases. Pasteur's personal discoveries had demonstrated the relation of certain lower organisms, notably the bacteria, to the contagious diseases, and had shown the possibility of giving immunity from certain of these diseases through the use of cultures of the noxious bacteria themselves. He believed that these methods could be extended and developed until all the contagious diseases, which hitherto have accounted for so startling a proportion of all deaths, were brought within the control of medical science. His deepest thought in founding the institute was to supply a tangible seat of operations for this attempted conquest, where the brilliant assistants he had gathered about him, and their successors in turn, might take a share in this great struggle, unhampered by the material drawbacks which so often confront the would-be worker in science.

He desired also that the institution should be a centre of education along the lines of its work, adding thus an indirect influence to the score of its direct achievements. In both these regards the institution has been and continues to be worthy of its founder. The Pasteur Institute is in effect a school of bacteriology, where each of the professors is at once a teacher and a brilliant investigator. The chief courses of instruction consist of two series each year of lectures and laboratory demonstrations on topics within the field of bacteriology. These courses, at which all the regular staff of the institution assist more or less, are open to physicians and other competent students regardless of nationality, and they suffice to inculcate the principles of bacteriology to a large band of seekers each year.

But more important, perhaps, than this form of educational influence is the impetus given by the institute to the researches of a small, select band of investigators who have taken up bacteriology for a life work, and who come here to perfect themselves in the final niceties of the technique of a most difficult profession. Thus such men as Calmette, the discoverer of the serum treatment of serpent-poisoning, and Yersin, famous for his researches in the prevention and cure of cholera by inoculation, are "graduates" of the Pasteur Institute. Indeed, almost all the chief laborers in this field in the world to-day, including the directors of practically all the daughter institutes bearing the same name that are now scattered all over the world, have had at least a share of their training in the mother institute here in Paris.

Of the work of the men who form the regular staff of the Pasteur Institute only a few words need be said here. Doctors Roux, Grancher, Metchnikoff, and Chamberland all had the privilege of sharing Pasteur's labors during the later years of the master's life, and each of them is a worthy follower of the beloved leader and at the same time a brilliant original investigator.*1* Roux is known everywhere in connection with the serum treatment of diphtheria, which he was so largely instrumental in developing. Grancher directs the anti-rabic department and allied fields. Metchnikoff, a Russian by birth and Parisian by adoption, is famous as the author of the theory that the white blood-corpuscles of the blood are the efficient agents in combating bacteria. Chamberland directs the field of practical bacteriology in its applications to hygiene, including the department in which protective serums are developed for the prevention of various diseases of domesticated animals, notably swine fever and anthrax. About one million sheep and half as many cattle are annually given immunity from anthrax by the serum here produced.

Of the patient and unremitting toil demanded of the investigator in this realm of the infinitely little; of the skill in manipulation, the fertility of resource, the scrupulous exactness of experiment that are absolutely prerequisite to success; of the dangers that attend investigations which deal with noxious germs, every one who knows anything of the subject has some conception, but those alone can have full comprehension who have themselves attempted to follow the devious and delicate pathways of bacteriology. But the goals to which these pathways lead have a tangibility that give them a vital interest for all the world. The hopes and expectations of bacteriology halt at nothing short of the ultimate extirpation of contagious diseases. The way to that goal is long and hard, yet in time it will be made passable. And in our generation there is no company of men who are doing more towards that end than the staff of that most famous of bacteriological laboratories the Pasteur Institute.

THE VIRCHOW INSTITUTE OF PATHOLOGY

Even were the contagious diseases well in hand, there would still remain a sufficient coterie of maladies whose origin is not due to the influence of living germs. There are, for example, many diseases of the digestive, nutritive, and excretory systems, of the heart and arteries, of the brain and nerves, and various less clearly localized abnormal conditions, that owe their origin to inherent defects of the organism, or to various indiscretions of food or drink, to unhygienic surroundings, to material injuries, or to other forms of environmental stress quite dissociated from the action of bacteria. It is true that one would need to use extreme care nowadays in defining more exactly the diseases that thus lie without the field of the bacteriologist, as that prying individual seems prone to claim almost everything within sight, and to justify his claim with the microscope; but after that instrument has done its best or worst, there will still remain a fair contingent of maladies that cannot fairly be brought within the domain of the ever-present "germ." On the other hand, all germ diseases have of course their particular effects upon the system, bringing their results within the scope of the pathologist. Thus while the bacteriologist has no concern directly with any disease that is not of bacterial origin, the pathologist has a direct interest in every form of disease whatever; in other words, bacteriology, properly considered, is only a special department of pathology, just as pathology itself is only a special department of general medicine.

Whichever way one turns in science, subjects are always found thus dovetailing into one another and refusing to be sharply outlined. Nevertheless, here as elsewhere, there are theoretical bounds that suffice for purposes of definition, if not very rigidly lived up to in practice; and we are justified in thinking of the pathologist (perhaps I should say the pathological anatomist) as the investigator of disease who is directly concerned with effects rather than with causes, who aims directly at the diseased tissue itself and reasons only secondarily to the causes. His problem is: given a certain disease (if I may be permitted this personified form of expression), to find what tissues of the body are changed by it from the normal and in what manner changed.

It requires but a moment's reflection to make it clear that a certain crude insight into the solution of this problem, as regards all common diseases, must have been the common knowledge of medical men since the earliest times. Thus not even medical knowledge was needed to demonstrate that the tissues of an in: flamed part become red and swollen; and numerous other changes of diseased tissues are almost equally patent. But this species of knowledge, based on microscopic inspection, was very vague and untrustworthy, and it was only after the advent of the perfected microscope, some three-quarters of a century ago, that pathological anatomy began to have any proper claim to scientific rank. Indeed, it was not until about the year 1865 that the real clew was discovered which gave the same impetus to pathology that the demonstration of the germ theory of disease gave at about the same time to etiology, or the study of causes of disease. This clew consisted of the final demonstration that all organic action is in the last resort a question of cellular activities, and, specifically, that all abnormal changes in any tissues of the body, due to whatever disease, can consist of nothing more than the destruction, or the proliferation, or the alteration of the cells that compose that tissue.

That seems a simple enough proposition nowadays, but it was at once revolutionary and inspiring in the day of its original enunciation some forty years ago. The man who had made the discovery was a young German physician, professor in the University of Freiburg, by name Rudolph Virchow. The discovery made him famous, and from that day to this the name of Virchow has held somewhat the same position in the world of pathology that the name of Pasteur occupied in the realm of bacteriology. Virchow was called presently to a professorship in the University of Berlin. In connection with this chair he established his famous Institute of Pathology, which has been the Mecca of all students of pathology ever since. He did a host of other notable things as well, among others, entering the field of politics, and becoming a recognized leader there no less than in science. Indeed, it seemed during the later decades of his life as if one encountered Virchow in whatever direction one turned in Berlin, and one feels that it was not without reason that his compatriots spoke of him as "the man who knows everything." To the end he retained all the alertness of intellect and the energy of body that had made him what he was. One found him at an early hour in the morning attending to the routine of his hospital duties, his lectures, and clinical demonstrations. These finished, he rushed off, perhaps to his parliamentary duties; thence to a meeting of the Academy of Sciences, or to preside at the Academy of Medicine or at some other scientific gathering. And in intervals of these diversified pursuits he was besieged ever by a host of private callers, who sought his opinion, his advice, his influence in some matter of practical politics, of statecraft, or of science, or who, perhaps, had merely come the length of the continent that they might grasp the hand of the "father of pathology."

In whatever capacity one sought him out, provided the seeking were not too presumptuous, one was sure to find the great savant approachable, courteous, even cordial. A man of multifarious affairs, he impressed one as having abundance of time for them all, and to spare. There is a leisureliness about the seeming habit of existence on the Continent that does not pertain in America, and one felt the flavor of it quite as much in the presence of this great worker as among those people who from our stand-point seem never really to work at all. This is to a certain extent explained if one visited Virchow in his home, and found to his astonishment that the world-renowned physician, statesman, pathologist, anthropologist was domiciled in a little apartment of the most modest equipment, up two flights, in a house of most unpretentious character. Everything was entirely respectable, altogether comfortable, to be sure; but it was a grade of living which a man of corresponding position in America could not hold to without finding himself quite out of step with his confrères and the subject of endless comment. But in this city of universal apartment-house occupancy and relatively low average of display in living it is quite otherwise. Virchow lived on the same plane, generally speaking, with the other scientists of Europe; it is only from the American standpoint that there is any seeming disparity between his fame and his material station in life; nor do I claim this as a merit of the American stand-point.

Be that as it may, however, our present concern lies not with these matters, but with Virchow the pathologist and teacher. To see the great scientist at his best in this rôle, it was necessary to visit the Institute of Pathology on a Thursday morning at the hour of nine. On the morning of our visit we found the students already assembled and gathered in clusters all about the room, examining specimens of morbid anatomy, under guidance of various laboratory assistants. This was to give them a general familiarity with the appearances of the disease-products that would be described to them in the ensuing lecture. But what is most striking about the room was the very unique method of arrangement of the desk or table on which the specimens rested. It was virtually a long-drawn-out series of desks winding back and forth throughout the entire room, but all united into one, so that a specimen passed along the table from end to end will make a zigzag tour of the room, passing finally before each person in the entire audience. To facilitate such transit, there was a little iron railway all along the centre of the table, with miniature turn-tables at the corners, along which microscopes, with adjusted specimens for examination, might be conveyed without danger of maladjustment or injury. This may seem a small detail, but it is really an important auxiliary in the teaching by demonstration with specimens for which this room was peculiarly intended. The ordinary lectures of Professor Virchow were held in a neighboring amphitheatre of conventional type.

Of a sudden there was a hush in the hum of voices, as a little, thin, frail-seeming man entered and stepped briskly to the front of the room and upon the low platform before the blackboard in the corner. A moment's pause for the students to take their places, and the lecturer, who of course was Virchow himself, began, in a clear, conversational voice, to discourse on the topic of the day, which chanced to be the formation of clots in blood-vessels. There was no particular attempt at oratory; rather the lecturer proceeded as if talking man to man, with no thought but to make his meaning perfectly clear. He began at once putting specimens in circulation, as supplied on his demand by his assistants from a rather grewsome-looking collection before him. Now he paused to chaff the assistant who was making the labels, poking good-humored jokes at his awkwardness, but with no trace of sting. Again he became animated, his voice raised a little, his speech more vehement, as he advanced his own views on some contested theory or refuted the objections that some opponent had urged against him, always, however, with a smile lurking about his eyes or openly showing on his lips.

Constantly the lecturer turned to the blackboard to illustrate with colored, crayons such points of his discourse as the actual specimens in circulation might leave obscure. Everything must be made plain to every hearer or he would not be satisfied. One can but contrast such teaching as this with the lectures of the average German professor, who seems not to concern himself in the least as to whether anything is understood by any one. But Virchow had the spirit of the true teacher. He had the air of loving his task, old story as it was to him. Most of his auditors were mere students, yet he appealed to them as earnestly as if they were associates and equals. He seemed to try to put himself on their level--to make his thought near to them. Physically he was near to them as he talked, the platform on which he stood being but a few inches in height, and such physical nearness conduces to a familiarity of discourse that is best fitted for placing lecturer and hearers _en rapport_. All in all, appealing as it does almost equally to ear and eye, it is a type of what a lecturer should be. Not a student there but went away with an added fund of information, which is far more than can be said of most of the lectures in a German university.

Needless to say, there are other departments to the Institute of Pathology. There are collections of beautifully preserved specimens for examination; rooms for practical experimentation in all phases of the subject, the chemical side included; but these are not very different from the similar departments of similar institutions everywhere. What was unique and characteristic about this institution was the personality of the director. Now he is gone, but his influence will not soon be forgotten. The pupils of a great teacher are sure to carry forward the work somewhat in the spirit of the master for at least a generation.

THE BERLIN INSTITUTE OP HYGIENE

I purposely refrain from entering into any details as to the character of the technical work done at the Virchow Institute, because the subject of pathology, despite its directly practical bearings, is in itself necessarily somewhat removed from the knowledge of the general reader. One cannot well understand the details of changes in tissues under abnormal conditions unless one first understands the normal conditions of the tissues themselves, and such knowledge is reserved for the special students of anatomy. For the nonprofessional observer the interest of the Virchow Institute must lie in its general scope rather than in the details of the subjects there brought under investigation, which latter have, indeed, of necessity, a somewhat grewsome character despite the beneficent results that spring from them. It is quite otherwise, however, with the work of the allied institution of which I now come to speak. The Institute of Hygiene deals with topics not very remote from those studied in the Virchow Institute, part of its work, indeed, falling clearly within the scope of pathology; but it differs in being clearly comprehensible to the general public and of immediate and tangible interest from the most strictly utilitarian stand-point, hygiene being, in effect, the tangible link between the more abstract medical sciences and the affairs of every-day life.

The Institute of Hygiene has also the interest that always attaches to association with a famous name, for it was here that Professor Koch made the greater part of those investigations which made his name the best known, next to that of Pasteur, of any in the field of bacteriology. In particular, the researches on the cholera germ, and those even more widely heralded researches that led to the discovery of the bacillus of tuberculosis, and the development of the remedy tuberculin, of which so much was at first expected, were made by Professor Koch in the laboratories of the antiquated building which was then and is still the seat of the Institute of Hygiene. More recently Professor Koch has severed his connection with the institution after presiding over it for many years, having now a semi-private laboratory just across from the Virchow Institute, in connection with the Charité Hospital; but one still thinks of the Institute of Hygiene as peculiarly the "Koch Institute" without injustice, so fully does its work follow the lines laid out for it by the great leader.

But however much the stamp of any individual personality may rest upon the institute, it is officially a department of the university, just as is the Virchow Institute. Like the latter, also, its local habitation is an antiquated building, strangely at variance, according to American ideas, with its reputation, though by no means noteworthy in this regard in the case of a German institution. It is situated in a part of the city distant from any other department of the university, and there is nothing about it exteriorly to distinguish it from other houses of the solid block in which it stands. Interiorly, it reminds one rather of a converted dwelling than a laboratory proper. Its rooms are well enough adapted to their purpose, but they give one the impression of a makeshift. The smallest American college would be ill-satisfied with such an equipment for any department of its work. Yet in these dingy quarters has been accomplished some of the best work in the new science of bacteriology that our century will have to boast.

The actual equipment of the bacteriological laboratory here is not, indeed, quite as meagre as it seems at first, there being numerous rooms, scattered here and there, which in the aggregate give opportunity for work to a large number of investigators, though no single room makes an impressive appearance. There is one room, however, large enough to give audience to a considerable class, and here lectures were given by Professor Koch and continue to be given by his successors to the special students of bacteriology who come from all over the world, as well as to the university students who take the course as a part of their regular medical curriculum. In regard to this feature of its work, the Institute of Hygiene differs in no essential respect from the Pasteur Institute and other laboratories of bacteriology. The same general routine of work pertains: the patient cultivation of the minute organisms in various mediums, their careful staining by special processes, and their investigation under the microscope mark the work of the bacteriologist everywhere. Many details of the special methods of culture or treatment originated here with Professor Koch, but such matters are never kept secret in science, so one may see them practised quite as generally and as efficiently in other laboratories as in this one. Indeed, it may frankly be admitted that, aside from its historical associations with the pioneer work in bacteriology, which will always make it memorable, there is nothing about the bacteriological laboratory here to give it distinction over hundreds of similar ones elsewhere; while in point of technical equipment, as already noted, it is remarkable rather for what it lacks than for what it presents.

The department of bacteriology, however, is only one of several important features of the institute. One has but to ascend another flight of stairs to pass out of the sphere of the microbe and enter a department where attention is directed to quite another field. We have now come to what may be considered the laboratory of hygiene proper, since here the investigations have to do directly with the functionings of the human body in their relations to the every-day environment. Here again one is struck with the meagre equipment with which important results may be attained by patient and skilled investigators. In only one room does one find a really elaborate piece of apparatus. This exceptional mechanism consists essentially of a cabinet large enough to give comfortable lodgment to a human subject--a cabinet with walls of peculiar structure, partly of glass, and connected by various pipes with sundry mysterious-seeming retorts. This single apparatus, however, is susceptible of being employed for the investigation of an almost endless variety of questions pertaining to the functionings of the human body considered as a working mechanism.