128 The Mechanistic Conception of Life 



believe that it may be of interest to the medical profession 

 to follow me in a brief survey of my experiments on artificial 

 parthenogenesis and the causation of the development of the 

 egg by a spermatozoon. 



I 



Cellular physiology has shown that tissues and organs 

 develop only from cells through nuclear and cellular division. 

 The conditions which cause cells to divide and to develop into 

 new normal or pathological tissues have, since Virchow, been 

 called formative stimuli. It is the task of modem biology to 

 ascertain first what is the nature of these stimuli, and second, 

 which change occurs in the cell in the process of formative 

 stimulation. Virchow already emphasized the fact that the 

 fertilization of the egg is the model of all phenomena of forma- 

 tive stimulation and that the spermatozoon may be considered 

 as the formative stimulus in this case. 



Pathologists have not yet succeeded in determining what 

 the physico-chemical nature of the formative stimulus in the 

 case of a tumor is, or what changes a cell undergoes in such a 

 process. This task has, however, been accomplished to a high 

 degree in the animal egg, and it may therefore interest the 

 pathologist and the physician in general to become familiar 

 with the essential features of the data thus obtained. 



It is known that aside from a few exceptions the animal egg 

 can only develop if a spermatozoon enters into it. If no sperma- 

 tozoon enters, as a rule no segmentation of the egg takes place 

 and it perishes after a comparatively short period of time. The 

 questions which I tried to solve were the following: By which 

 physico-chemical agencies does the spermatozoon cause the 

 egg to divide and to develop into an embryo; and second, which 

 changes does the egg undergo in this formative stimulation by 

 a spermatozoon ? Or in other words, what is the mechanism by 

 which the unfertilized egg is caused to segment and to develop ? 



