CHAPTER IV. 

 MECHANISM OF INFECTION. 



Infection or Contagion Virulence Immunity Refractory State. 



WE may deduce from what has preceded that, if vacci- 

 nations, either spontaneous or artificial, can increase the 

 resistance of the organism against spontaneous infection 

 by increasing within certain limits the parenteral digestive 

 power and probably also the digestive power of the intestines : 

 for the cells of the mucosa and of the intestinal glands may 

 quite as well as those of other tissues and organs participate 

 in the production of antibodies and distribute them partly 

 into the circulation and partly into the intestinal contents; 

 they (vaccinations) may at the same time increase the sus- 

 ceptiblity of the organism to the reaction of albumins and 

 thus put the organism into a state which we may rightly 

 call "anaphylactic." 



If then, as seems probable, bacteria of the colon-typhoid 

 group as well as cholera vibrios do not secrete a toxin- 

 antigen of a crystalloid poison, diseases caused by these 

 bacteria are nothing else than anaphylactic crises, whose 

 violence and duration is determined by the total of conditions 

 which we have analyzed above. 



In typhoid fever these crises may last for several weeks 

 and there is not one single crisis but a series of successive 

 crises. Paratyphoid may develop in the same way as 

 typhoid or much more quickly (in one or a few days) accord- 

 ing to the state of sensitiveness of the subject and the dose 

 of bacteria injected and the differences of development 

 depend principally upon differences in the rapidity with which 

 bacteria multiply. Cholera develops always very rapidly, 

 because the bacteria rapidly yield very abundant cultures 

 and also because bacteriolysis takes place rapidly. Colon 



