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SECT. XL 



OF THE NISUS FORM ATI VUS. 



583. HAYING simply described the phenomena of 

 conception and the changes which constant observa- 

 tion proves to occur both in the ovum and the con- 

 tained foetus during pregnancy, we now proceed to 

 those powers by which it appears that generation is 

 effected. 



584. Even in our memory, some physiologists of 

 reputation have contented themselves with roundly 

 asserting that true generation never occurs, but that 

 the whole human race pre-existed in the genitals of 

 our first parents, in the shape of previously-formed 

 germs which become evolved in succession. Some of 

 these imagined the germs to be the spermatic animal- 

 cules of the male ; * others imagined them to exist in 

 the ovaries of the mother.f 



* See "W. Fr. v. Gleichen, 1. c. 



f- v. c. The illustrious Hallcr, who plainly asserted, that all the viscera and 

 even the bones of the future fee tus, nearly fluid indeed, and therefore invisible, 

 were pre-formed, before conception, in the maternal germ. 



In support of this hypothesis, he argued chiefly from the continuity of the 

 membranes and blood-vessels between the incubated chick and the yolk of the 

 egg. Opera Minor a. T. ii. p. 418 sq. 



But the more frequently I have demonstrated the phenomena of incubation 

 in my Physiological Lectures, the less strength have I found in this argument. 

 Nor can I sufficiently wonder how this great physiologist could so constantly 

 reject, as almost absurd, the inosculation, properly so called, of the vessels of 



