RELATION TO INFECTIOUS DISEASES. 85 



Charrin and Roger have shown that white rats, 

 which are naturally immune to anthrax, become susceptible 

 when fatigued by being kept on a small tread-mill. Eleven 

 rats were inoculated with an anthrax culture ; five of these 

 which were allowed to rest in the cage manifested no symp- 

 toms of the disease, while six which were placed on the 

 tread-mill developed the disease and died within from 

 twenty-four to thirty hours. The bacilli were found in 

 the liver and spleen of those which died ; and guinea-pigs 

 inoculated with these germs died. The influence of the 

 condition of health on susceptibility to the infectious dis- 

 eases has also been shown by Leo, who found that mice 

 which are naturally insusceptible to glanders, become highly 

 susceptible when they are rendered diabetic by the admiflis- 

 tration of phloridzin. 



That some neurotic affections originate from traumatism 

 we know. That others of this class are largely due to mal- 

 nutrition accompanied by improper metabolism or insuffi- 

 cient elimination, or, in other words, are to some extent 

 autogenous, all believe. Understanding, then, that the 

 above classification does not attempt a sharp and marked 

 differentiation of the causes of disease, we will now give 

 our attention to a consideration of the chemical factors in 

 the causation of the infectious diseases, and of the trau- 

 matic, autogenous and neurotic, in so far as these are influ- 

 enced by infection. 



Recognizing the fact that germs do bear a causal relation 

 to some diseases, the question arises, How do these organ- 

 isms produce disease? In what way does the bacillus 

 anthracis, for instance, induce the symptoms of the disease 

 and death? Many answers to this question have been 

 offered. Some of the most important of these are as fol- 

 lows : 



1. It was first suggested by Bollinger that apoplecti- 

 form anthrax is due to deoxidation of the blood by the 

 bacilli. These germs are aerobic, and were supposed to 

 deprive the red blood-corpuscles of their oxygen. This 

 theory was suggested most probably by the resemblance of 

 the symptoms to those of carbonic acid poisoning. Tlie 



