146 THE CAUSATION OF DISEASE. 



impressionability of an organism to a specific E manifestly 

 depends upon inborn structure, and inborn structure depends 

 upon heredity. Wherefore, the readiness with which an organism 

 responds to a specific E depends upon heredity. In other 

 words, we inherit the fower of acquiring. 



So vast is the part played by Structure in determining 

 whether it shall vary or not, that Darwin maintained that 

 peculiarity in variation depends more upon the Structure of 

 an organism than upon the nature of its Environment. 



