Problems, Concepts and Their History 



philosophy as they were, are deep in much 

 of the embryological and indeed the wider 

 biological thinking both of the past and the 

 present. His description of the heart as the 

 first organ of the embiyo to be formed, both 

 in time and in primacy, tied as it was to the 

 conception of the soul as formal and final 

 cause and of vital heat in the blood as the 

 agent of the soul, dominated the notions 

 not only of the developing bvit also of the 

 adult circulation, and hence all physiology, 

 through to the nineteenth century and the 

 downfall of the phlogiston theory. His con- 

 cept of organ as related to final cause epito- 

 mizes teleology, and with all the weight of 

 Galen's authority in support still permeates 

 much of the thought of modern biology. 

 Matter with form inseparable from it as op- 

 posed to the more material matter postulated 

 by Leucippus' and Democritus' atomic the- 

 ory, which implied preformation, in a way 

 made possible the whole doctrine of epigene- 

 sis, first clearly formvilated by Aristotle and 

 still central in all embryological thinking 

 today. Form as inseparable from matter 

 makes possible a conception of pattern 

 emergent, an analogy of development and 

 the process of plaiting a net or the process 

 of painting a pictvire; for Plato, the Ideal 

 mesh would have been already woven, the 

 Ideal portrait previously complete. Aristotle 

 {Generation of Animals, 1943 edition, pp. 

 147, 149, 225) could frame the modern ques- 

 tion: 



How, then, are the other parts formed? Either 

 they are all formed simultaneously — heart, lung, 

 liver, eye, and the rest of them— or successively, as 

 we read in the poems ascribed to Orpheus, where he 

 says that the process by which an animal is formed 

 resembles the plaiting of a net. As for simultaneous 

 formation of the parts, our senses tell us plainly that 

 this does not happen: some of the parts are clearly 

 to be seen present in the embryo while others are 

 not. . . . Since one part, then, comes earlier and 

 another later, is it the case that A fashions B and 

 that it is there on account of B which is next to it, 

 or is it rather the case that B is formed after A? . . . 



In the early stages the parts are all traced out in 

 outline; later on they get their various colours and 

 softnesses and hardnesses, for all the world as if a 

 painter were at work on them, the painter being 

 Nature. Painters, as we know, first of all sketch in 

 the figure of the animal in outline, and after that 

 go on to apply the colours. 



The metaphor will speak for itself to mod- 

 ern experimental embryologists. Aristotle, 

 however, for all his natural acuity, was 

 strangely double-minded. In his dynamic 

 feeling for form, derived from direct study 



of living biological material, he was modern, 

 and was to lead eventually straight to the 

 inductive biology of modern times. But his 

 conceptions of the wider Universe, based on 

 pure reason, because statically and struc- 

 turally interpreted and thus transmitted by 

 medieval commentators, deluded posterity, 

 and it was unfortunately the static Aristotle, 

 the Aristotle of a sterile cosmogony, crystal 

 clear but crystal rigid, who dominated the 

 thought of the Middle Ages. So far as even 

 the embryology was concerned, the Middle 

 Ages transmitted his concepts, and occasion- 

 ally amplified them, as in the case of Al- 

 bertus Magnus, but devitalized them and 

 thereby hardly improved them. Appreciation 

 of their dynamic qualities awaited the Ren- 

 aissance and later ages. 



EMBRYOLOGY AND THE RENAISSANCE: 

 FABRICIUS, HARVEY 



When the Renaissance came under way it 

 accelerated its course into the new thought 

 by taking strength from the Greek past 

 through all the resources of Humanism; and 

 a "reconstruction of the Greek spirit" (cf. 

 Singer, ['41], p. 166) was an essential part 

 of the rebirth. Even Galileo has been called 

 a "typical Paduan Aristotelian" in method 

 and philosophy at least, if not in physics 

 (Randall, cited by Adelmann, ed., in Fabri- 

 cius, 1942 edition, p. 55), and Whitehead 

 ('25, p. 17) reminds us that Galileo "owes 

 more to Aristotle than appears on the sm*- 

 face of his Dialogues: he owes to him his 

 clear head and his analytic mind." Vesalius' 

 interpretations of his observations were as 

 teleological as those of Galen after which 

 they were modelled (cf. Singer, '44, p. 81, 

 who called him "a disciple of Galen by 

 training, by inclination, and by his whole 

 cast of thought"); his method, however, was 

 also in part that of Aristotle. Copernicus, 

 who was accused by Kepler of interpreting 

 Ptolemy, not nature, at least challenged the 

 Aristotelian cosmogony; Vesalius imitated 

 the method of the Aristotle who is so rarely 

 remembered as having written about an 

 embryological problem {Generation of Ani- 

 mals, 1943 edition, pp. 345, 347): 



This, then, appears to be the state of affairs ... so 

 far as theory can take us, supplemented by what 

 are thought to be the facts about their behaviour. 

 But the facts have not been sufficiently ascertained; 

 and if at any future time they are ascertained, then 

 credence must be given to the direct evidence of the 

 senses more than to theories. 



The scientist, who customarily characterizes 



