April 24, 1913J 



NATURE 



203 



interpreted and elucidated the whole mass of Aris- 

 totle's recorded erudition, which whole recorded mass 

 is only, after all, tanquam tabula naujragii. 



fhere is perhaps no chapter in the " Historia 

 Animalium " more attractive to the anatomist than 

 one which deals with the anatomy and mode of re- 

 production of the cartilaginous fishes, the sharks and 

 rays, a chapter which moved to admiration that prince 

 of anatomists Johannes Muller.' The latter wrote a 

 volume on the text of a page of Aristotle, a page 

 packed full of a multitude of facts, in no one of which 

 did Johannes Muller discover a Haw. The subject is 

 technical, but the gist of the matter is this : that 

 among these Selachians (as, after Aristotle, we still 

 sometimes call them) there are many diversities in 

 the structure of the parts in question, and several 

 distinct modes in which the young are brought forth 

 or matured. For in many kinds an egg is laid, which 

 eggs, by the way, Aristotle describes with great 

 minuteness. Other kinds do not lay eggs, but bring 

 forth their young alive, and those include the torpedo 

 and numerous sharks or dogfish. The eggshell is in 

 these cases very thin, and breaks before the birth 

 of the young. But among them there are a. couple 

 of sharks, of which one species was within Aristotle's 

 reach, where a very curious thing happens. Through 

 the delicate membrane, which is all that is left of the 

 eggshell, the great yolk-sac of the embryo becomes 

 connected with the parental tissues, which infold and 

 interweave with it; and by means of this temporary 

 union the blood of the parent becomes the medium of 

 nourishment for the young. And the whole arrange- 

 ment is physiologically identical with what obtains 

 in the higher animals, the mammals, or warm-blooded 

 vivipara. It is true that the yolk-sac is not identical 

 with that other embryonic membrane which comes 

 in the mammals to discharge the function of which 

 I speak; but Aristotle was aware of the difference, 

 and distinguishes the two membranes with truth and 

 accuracy. 



It happens that of the particular genus of sharks to 

 which this one belongs, there are two species differ- 

 ing by almost imperceptible characters; but it is in 

 one only of the two, the yn'hfw \c~ws of Aristotle, that 

 this singular phenomenon of the placenta vitellina is 

 found. It is found in the great blue shark of the 

 Atlantic and the Mediterranean ; but this creature has 

 grown to a very large size before it breeds, and such 

 great specimens are not likely to have come under 

 Aristotle's hands. Cuvier detected the phenomenon 

 in the blue shark, but paid little attention to it, and 

 for all his knowledge of Aristotle, did not perceive 

 that he was dealing with an important fact which 

 the philosopher had studied and explained. In the 

 seventeenth century, the anatomist Steno actually re- 

 discovered the phenomenon, in the ynXfor Xfinjj the 

 Mustela laevis itself, but he was unacquainted with 

 Aristotle. And the very fact was again forgotten 

 until Johannes Muller brought it to light, and showed 

 not only «how complete was Aristotle's account, but 

 how wide must have been his survey of 'his class of 

 fishes to enable him to record this peculiarity in its 

 relation to their many differences of structure and 

 reproductive habit. I ' used to think of this pheno- 

 menon as one that Aristotle might have learned from 

 the fishermen, but after a more careful study of 

 Johannes Miillcr's book, I am convinced that this is 

 not the case. It was a discovery that could only 

 have been made by a skilled and learned anatomist. 



I Cj Cavolini, in his classical 'Mem. sulla Generazione dei Pesci," 

 Naples, 1787: "EquanHoio . . scorro la Storia degli Animall dl Ans- 

 totile, non posso non ess-rp da stupore preso, in esse leggende veduti quel 

 fatti, che a noi non si son potntl che a sienlo manifestare : e rdevatl poi con 

 tntta lanettezza, e posti in parallelo coi fatti gia 

 gallo ; " &c. 



NO. 226g, vol. 91} 



In a lengthy and beautiful account Aristotle de- 

 scribes the development of tin; chick. It is on the 

 third day that the embryo becomes sufficiently formed 

 for the modern student to begin its study, and it was 

 after just three days (a little earlier, as Aristotle 

 notes, in little birds, a little later in larger ones) that 

 Aristotle saw the first clear indication of the embryo. 

 Like a speck of blood, he saw the heart beating, and 

 its two umbilical blood-vessels breaking out over the 

 yolk. A little later he saw the whole form of the 

 body, noting the disproportionate size of head and 

 eves, and found the two sets of blood-vessels leading, 

 the one to the yolk-sac, the other to the new-formed 

 allantois. In the tiny chick of the tenth day, he saw 

 the stomach and other viscera; he noted the altered 

 position of the heart and great blood-vessels; he 

 traced clearly and fully the surrounding membranes; 

 he opened the little eve, to seek, but failed to find, 

 the lens. And at length he describes in detail the 

 appearance and attitude of the little chick, the ab- 

 sorption of the yolk, the shrivelling of the mem- 

 branes, just at the time when the little bird begins 

 to chip the shell, and before it steps out into the 

 world. While this account contains but a part of 

 what Aristotle saw (and without a lens it would be 

 hard to see more than he), it includes the notable 

 fact of the early appearance of the heart, the punctum 

 saliens of later writers, whose precedence of all 

 other organs was a chief reason for Aristotle's attri- 

 buting to it a common, central, or primary sense, and so- 

 locating in it the central seat of the soul. And so it 

 was held to be until Harvey's time, who, noting 

 the contemporaneous appearance of heart and blood, 

 held that the contained was nobler than that which 

 contained it, and that it was the blood that was "the 

 fountain of life, the first to live, the last to die, the 

 primary seat of the soul, the element in which, as in 

 a fountain-head, the heat first and most abounds and 

 flourishes"; so harking back to a physiology more 

 ancient than Aristotle's— " for the blood is the life 

 thereof." All students of the "Timaeus" know that 

 here Aristotle parted company with Plato, who, fol- 

 lowing Hippocrates and Democritus, and others, 

 placed the seat of sensation, the sovereign part of the 

 soul, in the brain. Right or wrong, it was on ob- 

 servation, and on his rarer use of experiment, 5 that 

 \ristotle depended. The wasp or the centipede still 

 lives when either head or tail is amputated, the tor- 

 toise's heart beats when removed from the body, and 

 the heart is the centre from which the blood-vessels 

 spring. To these arguments Aristotle added the more 

 idealistic belief that the seat of the soul, the ruling 

 force of the body, must appropriately lie in the centre ; 

 and he found further confirmation of this view from 

 a study of the embryo plant, where in the centre, 

 between the seed-leaves, is the point from which stem 

 and root grow. And Ogle reminds us how, until a 

 hundred years ago, botanists still retained an _ affec- 

 tionate and superstitious regard for that portion of 

 the plant, calling it now cor, now cerebrum, the 

 plant's heart or brain. \ 



And now is it possible to trace directly the influence 

 of Aristotle's scientific training and biological learn- 

 in- upon his sociology, his psychology, or in general 

 on his philosophy? That such an influence must have 

 been at work is, prima facie, obvious. The physician 

 who becomes a philosopher will remain a physician 

 to the end- the engineer will remain an engineer; 

 and the ideas of pure mathematics, Roger Bacon's 

 "alphabet of philosophy," will find issue and expres- 

 sion in the philosophy of such mathematicians as 



5 Aristotle's 

 lis earden at 

 whether, or h. 



, who employed himself i 

 nd heads of snails, to se 



