40 POISONOUS PKOTEINS 



conditions. Virulence is largely determined by 

 rate of multiplication or at least the two cor- 

 respond. Under favorable conditions the chol- 

 era bacillus divides about every half hour. So 

 far as I know no one has determined the ' t gen- 

 eration period" in the tubercle bacillus, but it 

 is certainly much longer. It follows that cholera 

 is an acute disease, often terminating fatally in 

 a few hours while tuberculosis extends through 

 months and even years. The guinea-pig shows 

 no resistance to the tubercle bacillus and the or- 

 ganism slowly but steadily grows, develops its 

 characteristic lesions and kills, probably 

 through its autolytic products and without de- 

 veloping any antagonistic action in the body 

 cells. Eodents, especially rats, show but little 

 or no resistance to the plague bacillus, except in 

 those regions where this disease is endemic and 

 there, it is said, this disease even among the 

 rats becomes a chronic infection. 



Our intraperitoneal infection of the guinea- 

 pig is comparable with the development of a 

 general peritonitis from a ruptured appendix. 

 The period of incubation is short and while 

 there may be some elevation of temperature, 

 this is not marked or even constant. During 

 the period of incubation, when the bacilli are 

 abundantly multiplying, the behavior of the 



