94 Disease and Immunity 



food, or of some ingredient of food. An animal 

 weakene'd by starvation is more than normally 

 likely to fall a victim of some disease. 



When a person is worn down or exhausted 

 from long continued physical exertions he is 

 much more susceptible to bacterial infection than 

 when not so exhausted. Also, after a man has 

 been through a long illness due to some bacterial 

 infection, he is worn out and weak. These are 

 facts which show that the same energy used in a 

 physical struggle is the energy used in fighting 

 bacterial infection. The burden thrown upon a 

 man's powers by bacterial infection is called dis- 

 ease, but the similar burden thrown on the same 

 powers by an opponent or by some physically 

 observed and fully understood circumstances is 

 not disease. But wherein is the difference? In 

 both cases the physical powers are exhausted by 

 efforts which expend energy of the same kind. 

 Does a disease cease to be a disease when the 

 millions of cells which a man fights are organized 

 into large bodies instead of being separate 

 entities ? 



We can convert work fully and completely into 

 heat, but we can make the reverse transforma- 



