SECT, i] EMBRYOLOGY IN ANTIQUITY 75 



8. He foreshadowed the theory of recapitulation in his specula- 

 tions on the order in which the souls came to inhabit the 

 embryo during its growth, and in his observation that 

 universal characteristics precede particular characteristics in 

 embryogeny. 



9. He foreshadowed the theory of axial gradients by his observa- 

 tions on the greater and more rapid development of the cephalic 

 end in the embryo. 



10. He allotted the correct functions to the placenta and the 

 umbilical cord. 



11. He gave a description of embryonic development involv- 

 ing comparison with the action of rennet and yeast, fore- 

 shadowing thus our knowledge of organic catalysts in 

 embryogeny. 



But there was another side to the picture. Aristotle made three 

 big mistakes, and here I do not refer to any matters of detail, in 

 which it would not have been humanly possible to be more than 

 very often right, but rather to general notions, such as the eleven 

 correct ones. 



They were as follows : 



1. He was incorrect in his view that the male supplies nothing 

 tangible to the female in the process of fertilisation. To say 

 that the semen gave the "form" to the inchoate "matter" of 

 the menstrual blood was equivalent to saying that the seminal 

 fluid carried nothing in it but simply an immaterial breath 

 along with it. Aristotle did not envisage the existence of 

 spermatozoa. 



2. He was entirely wrong in his teaching about the scolex. The 

 caterpillar is not, as he supposed, an egg laid too soon, but has 

 already passed through the embryonic state. 



3. He was misled by some observations on castrated animals and 

 so did not ascribe to the testis its true function. 



Such mistakes as these, however, were not nearly so important as 

 the solid ground gained by his correct answers. They were always 

 open to experimental test, even though the authority of his name 

 precluded it until the Renaissance. But there was one aspect 

 of his embryological work which was to exercise an unfortunate 

 influence on the subsequent progress of the science, namely, his in- 

 sistence on teleological explanations. He was always seeking for 



