114 THE CONCEPTION OF LIFE 



usually from substances which we can easily see under suitable 

 conditions in the gland cells. When the gland functions, 

 these substances, which often may be seen as granules in 

 the protoplasm, are metamorphosed chemically, in order to 

 form the secretion which is given off by the gland. Very 

 exact recent investigations of these processes have been made 

 by the American, Bensley.^^ As we heard in the fifth lecture, 

 we can distinguish in the nuclei of sexual cells in many animals 

 a so-called chromosome which differs from the remaining 

 chromosomes. It claims our special interest because it 

 occurs in the cells of the female body, but on the contrary is 

 not found in the cells of the male body; hence, as we heard, 

 the hypothesis that these chromosomes determine the sex. 

 As we have already considered these relations, it will suffice 

 merely to mention the chromosomes. In conclusion let me 

 again direct your attention to the fact that always as we 

 grow old we can observe visible modifications of the cells. 



The phenomenon of metabolism and the phenomenon of 

 the visible alterations which can be observed in cells, lead to 

 the conclusion that the life processes are explicable by the 

 chemical properties and the structure of protoplasm and 

 nucleus. 



This explanation is called the mechanistic theory of life, 

 and has found acceptance with the majority of biologists. 

 It cannot be doubted that the mechanistic explanation is 

 stringently sufl&cient for most vital processes. Whether it is 

 sufficient to explain all the phenomena of life is a question 

 in regard to which opinions diverge. On one side there are 

 the Monists and their friends, and on the other the Vitalists 

 and Dualists. There are biologists who make a dogma of the 

 mechanistic theory and defend their doctrine with a vehe- 

 mence which recalls the theological discussions of the Middle 



