334 Comparative Anatomy — Its History, Aim, and Method 



profoundly affected all "natural philosophy" as, in course of the cen- 

 turies, it ramified into the several natural sciences. His contribution 

 to the factual knowledge of nature vastly exceeded in importance any- 

 thing that had yet been done, but much more important was his 

 abandonment of the speculative procedure of his predecessors and his 

 vigorous and convincing insistence that knowledge and understanding 

 of the truth must rest primarily on observation of fact. 



Fig. 272. Aristotle (384-322 B.C.). Bronze from 

 Herculaneum; in Naples Museum. Work of first 

 century A.D. from original of fourth century B.C. 

 (Courtesy, Singer: "The Evolution of Anatomy," 

 New York, Alfred A. Knopf, Inc.) 



Aristotle acquired an extensive knowledge of the animals which 

 were accessible to him. He recognized some 500 kinds of vertebrates 

 and many invertebrates. He learned much about the development of 

 the chick in the hen's egg and about the reproductive processes in 

 fishes. Especially noteworthy was his discovery that certain small 

 sharks (dogfishes) do not "lay eggs," as do most fishes, but are vivipa- 

 rous, and that the young fish developing within the maternal body 

 possesses nutritive arrangements resembling the placenta of viviparous 

 mammals. 



Most remarkable was Aristotle's anticipation of the essential prin- 

 ciple which, 2000 years later, was elaborated into the Theory of Evo- 



