the following articles are offered merely as contributions thereto. The work involved has, of necessity, consisted largely in the collection and arrangement of data, and endeavor will be made to give credit wherever due. In the first few chapters (dealing with the physiologic concepts of the "ancients") greater effort will be made to state clearly the views of the writers mentioned than to discuss their probable significance, endeavoring in every instance to keep within the bounds of fact and probability, and to avoid, or merely state as such, any disputed points. In the subsequent chapters, the newly developed facts, statements and hypotheses will be discussed in relation to, or on the basis of, the old, the main object being to trace (in outline at least) the development of animal, and especially of mammalian, physiology, from the view-point of a student of physiology rather than that of a student of history.

I.

THE BEGINNINGS OF PHYSIOLOGY.

It is probable that even in paleolithic times men were, in some measure, acquainted with the phenomena of nature in the midst of which their lives were spent. Not that primitive men actually sought and studied natural phenomena, but rather that the more conspicuous of these were thrust upon them. As Huxley has tersely stated, "In its earliest development knowledge is selfsown. Impressions force themselves upon men's senses whether they will or not, and often against their will;" such knowledge being "rather brought than sought" (9: pp. 2-3). The very survival of these primitive nomads not only necessitated the frequent killing of animals, but also involved some acquaintance with the habits of their animal enemies, and of those animals which yielded them food. It is not improbable, therefore, that they were cognizant of distinctions between living and dead animals, and their habitual use of the flesh of some animals for food, of the skins for clothing, and of the bones for purposes of ornament and defence, suggests that they crudely distinguished certain body-parts. The engravings of the mastodon, deer, bear, horse, bison, ibex, and other animals, found among the remains of paleolithic cavedwellers, afford evidence of the knowledge possessed by at least some of these men, of the forms, characteristic attitudes, and power of locomotion of the animals depicted, and indicate a degree of intelligence, the possessors of which could scarcely have failed

to observe such striking phenomena as the flow of blood from a severe wound and the warmth of the body of a living as compared with that of a dead mammal or bird.

Early in the neolithic period the dog was domesticated, and later the sheep, goat, ox, pig, and horse; the last named probably not until some time during the "bronze age." The successful domestication of these animals not only involved some knowledge of the habits of each, but in all likelihood also evolved a more intimate acquaintance with their individual and specific characteristics. Certain of the burial ceremonies prevalent during the "bronze age" (though of earlier origin) clearly indicate the early general acceptance of a belief to the effect that within the body of a living man, or animal, there dwells a somewhat that survives bodily death—a something potential rather than substantial, but without which the animal is inert, dead, and which therefore is causal of animal life.

The Accadians believed each natural object to possess a spirit, while the Sumerians distinguished a number of body-parts, and even entertained some crude physiologic concepts. They considered a living animal to consist of a body and a spirit; the body being composed of flesh moistened by blood (of which latter they distinguished a light and a dark variety) which they looked upon as the (chief) living constituent of the body. They considered the liver to be the central organ of the blood, the heart that of the understanding, and the ear that of the will. Of the uses of the limbs, lips, and eyes they entertained correct, though crude notions (15: pp. 58-59). Thus as early (probably) as the 38th century B.C. (cf. 16: pp. 114 and 295; 17: pp. 40-41) these pre-Semitic inhabitants of Babylonia considered the body to be made up of special parts (organs) adapted to the execution of particular functions, and the whole to be governed by an indwelling spirit (or spirits).

Though the date of writing of the Ebers Papyrus-from which so much of our information concerning Egyptian medicine has been obtained-has not yet been accurately determined, Ebers has stated that "with a degree of probability bordering upon certainty" it was drawn up some time during the three years from 1553 to 1550 B.C. (11: p. x), and Joachim, after an examination of the evidence, concludes that it was written at the latest about 1550 B.C. (11: p. xii). The papyrus itself bears evidence that it is (in part at least) a compilation of still older medical papyri. In paragraph CIII a medical writing or book is referred to "which was

found under the feet of the god Anubis in the city of Letopolis" (or Sekhem), and presented to the king Usaphaïs (also known as Hesepti and as Semti). What seems to have been the same book is also referred to in the Berlin Medical Papyrus, and it is there stated, in addition, that after the death of Usaphaïs (Semti) this book was given to Sent (11: p. 185). According to Budge (4: vol. I. pp. 194 and 214), Semti, who was the fifth king of the First Dynasty, reigned about 4266 B.C., and Sent, who was one of the kings of the Second Dynasty, reigned about 4000 B.C. Joachim gives the date of the reign of Usaphaïs (Semti) as about 3700 B.C. (11 p. 185). The present state of Egyptology does not, of course, warrant the acceptance of any of these dates as accurate, yet it seems probable that at a very early period-as early as, or earlier than, the 37th century B.C.-certain learned Egyptians entertained definite concepts concerning the treatment of certain diseases. There is also indirect evidence that the importance of moisture (i.e., water) and air for the maintenance of animal life, was recognized at a very early date; though in the present state of uncertainty concerning Egyptian chronology in general, and the dates and sources of the several medical papyri in particular, any attempt to trace the progress of physiologic concept in Egypt during the twenty-five or more centuries preceding the supposed date of the Ebers Papyrus would seem futile. It is highly probable, however, that as early as the middle of the 16th century B.C., Egyptian physicians had accumulated considerable clinical knowledge, had acquired some degree of surgical skill, and employed quite an extensive materia medica (cf. 11 and 15). There is likewise but little doubt that the study of human and mammalian anatomy was pursued, at irregular times perhaps, but with some degree of success, and that a series of physiologic concepts, some of which may have been quite fanciful, formed part of the medical knowledge of the time. The animal body was supposed to be ultimately composed of four "elements" and to be governed by four or more spirits. The writer has nowhere found definite descriptions or characterization of these “elements.”

(and later.)

THE EGYPTIANS. Bony or hard parts were distinguished from 16th century B.C. fleshy or soft parts, and three sorts of vessels, or conduits, were designated as traversing the soft part, viz., "air vessels" (bronchi? arteries?), "blood vessels" (veins?), and more solid conduits (probably including nerves, tendons, and small arteries). The following assertions concerning the vascular

system are made in the Ebers Papyrus as translated by Joachim (though not all of them are here given in the exact words of the translator): The heart is connected by vessels, or conduits, with all parts of the body. When the physician, priest, or wise man, places his hand on the epigastric (or cardiac?) region, on either arm, on the legs, he everywhere feels, or appreciates, the heart, from which vessels extend to all the members, and which, therefore, is the centre of all the vessels. There are four vessels, or conduits, in the nasal cavities, of which two yield mucus, and two blood. There are four vessels within the temples, which give blood (and water?) to the eyes. There are four vessels which divide in the head and spread out in the back of the head. There are two vessels to the right, and two to the left ear. The breath of life goes in the right ear, and the breath of death in the left ear; or, in other words, the breath of life enters the right side, and the breath of death the left side. Three vessels go to the right and three to the left arm, extending to the fingers. Three vessels go to the right, and three to the left foot. Two vessels go to the testicles, yielding semen. Two vessels to the kidneys; one to each. Four vessels to the liver, conducting to it moisture and air. Four vessels to the rectum (colon?) and to the spleen, conducting to these organs moisture and air. Two vessels to the bladder, yielding urine. Four vessels to the buttocks, conducting moisture and air, and thence extending to the feet (II: pp. 180-2). From these statements it is clear: First, that the arterial pulse was appreciated and attributed to the heart; second, that the vessels were thought to supply moisture and air to certain at least of the body-parts; third, that mucus, urine, and semen were supplied by, or derived from, the vessels.

Von Oefele states that the ancient Egyptians compared the pulse with the overflow and subsidence of the Nile (15: p. 85). They seem to have conceived of the blood as moving; not, however, as flowing like the water of a river, but as overflowing and subsiding a sort of tidal movement; the flesh being soaked with blood during the overflow, and the subsequent subsidence leaving it well moistened, and hence, according to their concept, in better condition for life and growth; somewhat as the land submerged by the Nile overflow is, after the subsidence of the river, in a better condition than before for the growth of crops (cf. 15: p. 81). Air (or possibly something similar to the Greek "pneuma") and the body-liquids were considered essential to animal life; the harmful. portions of these being eliminated, during life, by means of urine,

sweat, nasal discharges, eructations, and intestinal flatus, and their total expulsion resulting in mummification (cf. 15: pp. 81 and 85). In the Ebers Papyrus (II: p. 181) occurs the statement that the breath enters the nose and penetrates to the heart and intestines (abdominal contents?), and is abundantly supplied by the vessels to the body. Disturbance of digestion is several times mentioned, and also "putrefaction of feces," and numerous prescriptions for the relief of constipation are given, but thus far the writer has found nothing indicating that distinct ideas concerning digestive processes were entertained by them, though one passage indicates that they considered the heart or stomach to assimilate nutriment (II: p. 70). Displacements of the uterus are mentioned in the Ebers Papyrus, and directions given for the treatment thereof, and von Oefele states (15: p. 76) that, according to a "gynecological papyrus" supposed to have been written between 2230 and 2100 B.C., a sort of swaying or wandering movement seems to have been ascribed to the uterus. Vision was referred to the eyes, hearing to the ears, taste to the palate, and speech to the mouth (14: pp. 69-70; 4: Vol. II, p. 148), but the writer has thus far found no evidence that any rational explanation of sensation, bodily movement, or speech, was offered. Some mental states were referred to the heart, and in the book of Ptah-hotep the gradual decay and dissolution of old age is briefly described (14: pp. 69-70; 4: Vol. II, p. 148). It is difficult to determine whether or not body heat was reckoned as an essential factor in animal life. Von Oefele (15: p. 83) seems to think that it was.

From certain of the medical classics of India-especially from the writings of Susruta, Charaka, and Vágbhata-a crude system of physiology may be culled, which, though somewhat more rational than that of the Egyptians, is yet quite fanciful. It may be summarized as follows: Three fluids, viz., air, bile, and mucus, permeate the body. Air resides chiefly in those body-parts between the feet and navel; bile, in those between the navel and the heart; and mucus, in those between the heart and the crown of the head. Each of these fluids contends for supremacy; mucus prevailing during childhood, bile during adult life, and air in old

From these three "body-fluids" arise the "corporeal elements," which are chyle, blood, flesh, fat (or cellular tissue?), bone, marrow, and semen. Chyle is formed from food, and, in the liver and spleen, is transformed into blood. From blood, flesh is formed; from flesh, fat (cellular tissue?); from fat, bone; from bone, marrow; and from marrow, semen, both male and female (?). For the completion of this series of transformations