40 INFECTION 



destroyed, and those left develop more slowly, producing a tuber- 

 culosis in normal course of time. It is possible to immunize animals 

 against this aggressin producing an anti-aggressin, which substance 

 will not only neutralize the aggressin but also stimulate the leuco- 

 cytes to phagocytosis. 



This aggressin theory has been applied to other infections with 

 like results, notably in pneumococcus, typhoid, dysentery, and 

 plague infection. 



