In the flitting thought of Herodotus and in the more circumstantial elaboration of Aristotle, in natural selection and in pangenesis we have the two leading ideas of the method of evolution as they existed in the mind of Darwin. Lesser men who have come after him have for the most part had room for only one of them in their cranial cavity. Men who preceded him by some 2500 years were in the same plight, but the pangenesis germ sprouted in their minds, while in the minds of those who followed and out-Darwined Darwin the germ, minute as we have seen it in Herodotus, Anaximander and Empedocles, became the inconceivable germ plasm of Weissmann in his early days. I am free to say that I do not perceive that Burnet and especially Gomperz are justified in drawing the parallel quite so closely between the old and the new evolutionary theories. The ancient nature philosophers, Parmenides, Alcmaeon and Empedocles, like Galton, all drew the simple conclusion that the resemblance of mental and physical characters of the offspring depends on the proportion in which the seed of the parents enters into the constitution of the offspring. Ætius reports that Empedocles believed that the offspring were affected by maternal impressions, a firmly held doctrine of more modern times-or by the fancy of the woman at the time of conception-the basis of the philosophical story of Goethe-Elective Affinities-"for oftentimes," he says, "women fall in love with images and statues and bring forth offspring like these."17

So we recognize the vagaries as well as the other details in the evolutionary doctrine of the day which are useful in allowing us to perceive the very quintessence of a belief in the modifiability of the germ plasm. We see that even at that dawn of history this doctrine, familiar to us in the works of Hippocrates and of Aristotle, was original

17 Fairbanks, Arthur, "The first Philosophers of Greece," New York: Charles Scribners' Sons, 1898.

with neither. We may easily go back of Empedocles, who so influenced them both and who said: "it is not the difference in the vines that makes the wine good or bad, but in the soil which nourishes them.18 In the views of Empedocles, not only the nourishment of plants but perception of animals by the senses is effected by the attraction of kindred elements through their pores from the earth in which they grow and by the environment from objects of sensory emanations. These emanations are themselves an idea of primitive man. In another essay 19 I have drawn attention to the conception of the Australian savage and of other men scarcely less primitive who conceive of the soul as emitting emanations from its tenement in the body of a magician which may be blown by the winds into the patient. They pass unseen through the pores of the witch doctor into those of his patient who sits in his lee. The conception of the soul which leaves the body temporarily often existed in the primitive mind in a sense similar to our demonstration of radial matter. The emanations of the soul of the savage may be considered the prototype of the sense emanations of Empedocles. Many primitive men have this conception of the radial energy of the human soul, and it is not at all difficult to follow traces of it into the science and the philosophy and especially into the religions of the modern world.

As to the senses Empedocles supposed that the percepts of the mind arrive there through the sense organs by pores which admit the emanations from objects visualized or noises heard, or odors smelt, savors tasted, surfaces touched. Of specific kinds these emanation atoms are recognized by like specific kinds within the organization

18 Burrows, Ronald M., "Discoveries in Crete," New York: E. P. Dutton, 1907.

19 Wright, Jonathan, "Blood and the Soul." N. York M. J., July 20, Aug. 10, Aug. 17, 1918.

of the percepient by the soul. Empedocles was the great homoeopathist. Out of this form which homoeopathic or sympathetic magic took in the doctrines of Alcmæon and Empedocles and Aristotle and the followers of the latter for two thousand years sprang the firm conviction of mankind in the inheritance of acquired characters. Like attracts like and like begets like. The idea is inherent in the magic of primitive man so prominently that ethnologists epitomize its manifestations under the heading of homoeopathic magic. Neither primitive man nor Empedocles nor Hippocrates nor Aristotle nor their followers up to the middle of the nineteenth century ever had any other thought than that the race of men or the race of plants was governed in the manifestations of its heredity by the environment in which its ancestors have been placed. The whole order of the thought of mankind was indeed, until very recent times, pantheistic, an order in which kindred enamations of a universal spirit pervaded all nature and modified one another both somatically and in their heredity. The idea that there was something in nature not affected by its environment, spirit or body, soul or matter, at once placed it in a new category of mysticism, essentially modern.

The old order of thought is plainly manifested in the conceptions of a larger and larger class of cosmic phenomena, the further back we go in tracing the history of thought. As knowledge has advanced, one thing after another has emerged from the realm of mysticism and taken its place in the domain ruled by natural law. Empedocles and Aristotle thought their explanation placed heredity there, inefficient as it is in the ultimate analysis, but it remained for the nineteenth century biologists to place it back again in a new realm of mysticism by separating germ plasm from all other cosmic phenomena. It is the only thing which, we are now asked to believe, is unaffected by any of the rays of the

environment Empedocles had in mind when he postulated his theory of the rays, which we have identified in chemistry, in physics and in biology. The forces of nature, as open to the observation of the savage and of Hippocratic Greek as to our own, we are assured have no influence on the germ plasm or on the units into which it is being subdivided.

I am eluding all responsibility for the truth or the error of such a conception. All I mean to say is that, although this basis lies outside of the reasoning powers of man so far as they attempt to conceive of a material object unaffected by the proximity of another material object, it is a perfectly practical one upon which to rest certain phenomena in biological classification, which is always a provisional and temporary adjustment. It is practical and of value because it allows biologists to separate them into two categories:-one in which no proof exists that environmental influences have any effect-one in which such proof does exist. There has been a ceaseless shifting from the first to the second category since this basis was adopted by an influential school in biology, and this capability to provide for future results attests its practical value. Anything that is clearly shown by evidence to be modified in its potentiality is not germ plasm. As soon as certain transmitted characters are shown to be changed, then the hypothetical units of the germ plasm on which they depend must be removed from the terms of the general hypothesis. Simply because a person might differ from his grandfather, owing to his father's having lived in a different climate, has not until comparatively recent times seemed sufficient reason for removing the phenomenon from any dependence on the true germ plasm.

It was about twenty-four hundred years after the death of the author of "Airs, Waters and Places" that such an idea found lodgings in the brain of man. Unnoticed by

its advocates, so far as I have observed, it takes its place alongside of the eternal and unchanging things whose existence we are forced to acknowledge but of which we can have no conception. If it is a reality, we must accept it as we must the actuality of time and space, something lying outside of every possibility of reasoning by analogy. Though Weismann himself finally recoiled before this logical deduction, it is not necessary here to decide whether we are as yet really driven to this desperate refuge or not. It is entirely sufficient here to draw attention to a possible reason why Hippocrates introduced, as such important factors in the etiology of disease, the environment of the air we breathe, the water we drink and the localities we inhabit, things which modern medicine for the most part seems to ignore which we actually do ignore in our nosology. It was the absence of this miracle of the nineteenth century germ plasm, this unthinkable formula from the thoughts of men.

He had an added incentive for doing so. He believed they influenced not only the mortal body of man, but his soul and his heredity. When they enter into our consideration it is in the course of an enthusiasm for the therapeutical value of sunlight and fresh air in their effects on the tubercle bacillus, supposed to be wholly made up germ plasm, in the course of our observation of the effect of heat and moisture on various protozoal agents of disease whose albuminoids are, I infer, not wholly germ plasm, or in the course of dietetic studies which convince us that in certain localities the human organism assimilates, less readily than elsewhere, food of high caloric value.

In a historical essay, such as this pretends to be, I can thus enter into the modern biological argument only far enough to suggest it as one very important reason why Hippocrates seems to have exaggerated and why we very likely underrate the factors of air, water and localities in our

classification of disease etiology. Granting that this is an important reason, we may understand why the older commentators assumed a more sympathetic attitude toward this part of Hippocratic doctrine, and why, as we approach the era of Darwin, it recedes from discussion; notwithstanding the fact, entirely obvious to the quick perception of the student of modern medicine, that I am making the very scantiest allusion possible to other fields of modern research, very much affected indeed by considerations of airs, waters and localities. We cannot fail to realize, that, lately, in a historical sense, the advent of Darwinian doctrine and its further development in biology has radically changed our views of the effect of environment on disease. We have our ways of studying its connection with disease which differ from those of Hippocrates, and it will be interesting, biologically as well as historically, to take note of this difference.

It will not be entirely devoid of historical interest, at least, to see how Hippocrates made these factors influence not only the diseases of man, but, as I have foreshadowed, the nature of man itself. Of late years there have been undercurrents of opinion among ethnologists which deprecate extreme notions as to the racial differences of men, which to some extent are identifiable with ideas of stable elements in the human germ plasm in the conception of the biologist.

The idea seems to be that there is in reality one race of men whose somatic attributes are modifiable by the environment, climatic, as well as social and intellectual, but on the whole, this once eliminated, mankind is all much alike, especially from a point of view of brain capacity. I do not know that Hippocrates discusses the latter at all aside from his view, which agrees largely in fundamentals with this order of thought among ethnologists, but differs radically from that of the Weismannian or

ultra Darwinian theory. So far as the principle is concerned, he made no discrimination between the effects of the environment on the body and on the soul of man, on his mortal and his immortal part, on his soma and on his germ plasm, if you will, for I know of no other class than that of the soul, in Hippocrates' conceptions, in which to place the germ plasm. In reality as I have sufficiently insisted, it is something new, a third order of mental concept, partaking of the body in its manifestation and of the soul in its immortal nature, if we are to speak of the germ plasm in terms of the Hippocratic philosophy. I shall speak only of malaria here in its relation to the attitude he evinces towards the question which has for fifty years interested modern biologists.

MALARIA

Hippocrates emphasizes the differences which he declares exist between inhabitants of Asia and Europe. He says the environment of one continent had made the people quarrelsome, assertive, independent, brave, and the environment of the other across the narrow seas had rendered them mild, temperate, indolent, soft and cowardly. He does not develop his argument far in explanation of this, but his critics have, it seems to me, missed the only indication he gives of how he explained to himself the manner in which this change comes about. He recognizes that the warlike and the courageous themselves will be changed by the institutions under which they live.

No one will dispute his assertion that it is the change from the mean of climate that stimulates the physical and intellectual energies of men to activity. When, through the influence of an equable climate of a high temperature, those subjected to it have fallen under the sway of political institutions such as the ancient oriental monarchies, it becomes obvious to the dullest that their bravery, their vigor and their self denial are called into play for the exclusive benefit of

those invested with the supreme power. Into this order of thought we must introduce modifications. We know that Asiatics may be brave men and, even if they are not capable of sustained vigor of mind, they often exhibit a contempt of life and a readiness to die, equal, at least, to anything Hippocrates had observed among the victorious Greeks of his day. He had not seen Asiatics or Africans fired with the visions of Paradise. If the religions of Christ, of Mohammed and of the Mahdi had been phenomena of his day, raised up to counterbalance the pains of this life, he would have realized that there are other institutions, besides the political organizations of freedom, which are quite as capable of stimulating the furious valor of countless millions of men. But he knew only those political and social institutions which could do this and which make life worth while to free men. He did right in recognizing, as did Xenophon and many others, that it was the intellectual and political freedom of their cities which made men ready to die for the glories of Greece. Fanaticism, which, as we have known it in the annals of history for two thousand years, also makes men quite as ready to die, was a closed book to him. Devotion to a local god or to the heterogeneous assortment on Olympus was not calculated to inspire men with the maddened desperation to which the Prophet spurred on his Arabians, panting for the sensual joys of Allah, or with the valor which strove for the beatitude kept under the keys of Rome, and which carried the cross as well as the crescent through the blood of a thousand fields of battle both in Asia and in Europe.

These are phenomena, knowledge concerning which the world has garnered from the annals of history and stored up as the wisdom of ages since the days of Hippocrates; but he knew the political causes of cowardice and lethargy in men as well as we. The phenomena of fanaticism and faith

are "institutions," which change cowardice into courage, but they were not the institutions Hippocrates had in mind. He had in mind the political institutions and the ideals, inherited from brave ancestors, for which men have just died on the battlefields of Europe. So far, then, as he seems to have had some sort of hereditary influence in mind, affecting the nature of man, it was a social heredity; a kind of heredity we recognize in which, at least, the modern germ plasm plays a secondary, and the environment a primary rôle. I fancy none of us, neither the modern Lamarckian nor the Weismannian, would claim that such environment as works through social and political institutions upon the social and moral impulses of men has any effect upon the physical nature of man, but this confusion of social heredity with biological heredity often unconsciously invades the sense of modern discourses on the biology of man and his institutions.

The analogy to biology has always been pushed to ridiculous limits by the sociologists. It is likely to lead them far astray in theory, whether the biological theory is right or wrong, but it can hardly fail to do so when the model they pattern after is itself wrong. In practice "the survival of the fittest" has been the shibboleth in the present politico-social convulsion which has brought death and innumerable woes to many. If the unwary of today are betrayed into these lapses of logic and on the other hand apply to biological phenomena, including social phenomena, a charge to which Herbert Spencer himself was open, we can hardly expect such analytical discrimination could have been appreciated by the immediate successors of the Nature Philosophers of 2,500 years ago. However, I think it can be perceived from the text that Hippocrates was not entirely oblivious to the differentiation which today is imperative. In this analysis, revealed only by the introduction of his reference to institutions, there is of course no conception

of the intermediaries through which his airs, waters and places work in producing disease. He perceived, perhaps, that it was through "institutions" that the climate worked upon the nature of men, but he had no inkling that there were different intermediaries through which the climate worked to cause the diseases of men. He traced to climate and locality, as causes, the phenomena of the moral nature of man, and he was instinctively right in reasoning by analogy that they were also often the causes of his diseases. The sickliness, the jaundice, the "quartan fevers," the lack of bodily and mental vigor, he was right in bringing into relation with the winds, the waters and the sun exposure. This time there was no "institution" to interpose as a direct influence, but there was an institution—a micro-organism of which he knew nothing but the results. It was hidden from him just as the fanaticism, from which the Greek world was free, was hidden from him. One of the factors influencing the moral nature of man and one of the factors influencing the bodily nature of man were alike absent from his field of observation. It is not directly the sun's heat, nor the fog and moisture of the marsh lands, it is not the failure of the breezes which parch up the veins of the sons of men who dwell there or relax the flesh of their bodies and change the color of their skins to a yellow hue. (However, these are the elements in the environment which call into existence the two links we have discovered during the last generation in the chain of causation.) It is the anopheles fasciata, it is the plasmodium which it carries that stands between the factors with which Hippocrates and, Littré and Adams were familiar-airs, waters and places-and ague. It is the parasite of Laveran which alters the blood their fathers have transmitted to them, not the forces of nature which have altered the heredity of men.

It is quite impossible to know what type