DEFECTIVE STATE OF PHYSIOLOGY. 21 



exertions of morphologists, and not of physiologists. Indeed 

 the direction at present taken by Physiology is so one- 

 sided that it has even neglected the recognition of the most 

 important functions of Evolution, namely, Heredity and 

 Adaptation, and has left this entirely physiological task to 

 morphologists. We owe to morphologists, and not to physi- 

 ologists, nearly all that we yet know of Heredity and 

 Adaptation. The latter still works as little at the functions 

 of evolution as at the evolution of the functions. 



It will, therefore, be the task of a future Physiogeny to 



grasp the history of the evolution of the functions with the 



same earnestness, and with the same success, with which 



Morphogeny has long ago undertaken the study of the history 



of the evolution of forms. A few instances will show how 



closely the two are connected. The heart of the human 



embryo has at first a very simple structure, such as appears 



permanently only in Ascidians and other inferior Worms, 



and connected with it is a circulation of the blood of 



the most simple kind. When, on the other hand, we see 



that with the fully developed form of the human heart there 



is connected a function of the circulation of the blood totally 



different from the former one, and far more complicated, the 



study of the evolution of the heart necessarily enlarges 



from a task which was originally morphological to one 



which is physiological also. It is the same in the case of 



all other organs and their activities. 



Thus, for instance, a careful comparative study of the 

 history of the evolution of the form of the intestinal canal, 

 the lungs, and the organs of generation, affords us also most 

 important information as to the evolution of the respective 

 functions of these organs. 



