BACTERIAL PROTEINS 39 



these are all destroyed, there is no multiplica- 

 tion and the ampunt of poison set free in the 

 destruction of the small number of the invaders 

 is not sufficient to induce symptoms or to de- 

 velop lesions. This is what happens when the 

 smallpox virus finds its way into the body of 

 one thoroughly immunized by a previous attack 

 of the disease or by successful vaccination. 

 When the immunity is only partial or when the 

 infection is massive or unusually virulent, , the 

 virus develops for a time, becomes more or less 

 distributed in certain tissues and its final de- 

 struction is accompanied by the development of 

 symptoms, and the reaction between the virus 

 and the body cells leaves more or less marked 

 lesions. When there is no immunity the virus 

 multiplies without hindrance and life is de- 

 stroyed. There are infections in which the 

 body shows little or no resistance. Some of 

 these run an acute course and destroy life in a 

 few days, while others are more chronic. This 

 seems to depend upon the rate of multiplication 

 in the invading organism. Apparently there is 

 relatively as much difference in the rate of mul- 

 tiplication in bacteria as there is among the 

 higher animals. The "generation period " or 

 the interval between fissions varies among spe- 

 cies and strains, and is influenced by external 



