BACTERIOLOGY. 



different kinds of bacteria and bacterial pro- 

 ducts, and it was at once recognized that the 

 basis for this result lay in the rendering active 

 both of the ordinary cellular defensive elements 

 of the body and of those chemical elements that 

 have gone into solution, although Klein er- 

 roneously supposed that the bacteria employed 

 in these experiments form the same poison as 

 that formed by the cholera germ and bring 

 about their protective effect by causing an 

 habituation to their poison. These first ex- 

 periments were prompted by certain unex- 

 pected results of investigation. The discovery 

 was made that if we introduce into cultures of 

 parasitic bacteria micro-organisms of a different 

 sort, as, for instance, the bacilli of blue-green 

 pus into cultures of anthrax bacteria, the latter 

 grow more feebly. These experiments belong 

 in the class of antagonistic effects described 

 on p. 119. In such cases, there could be no 

 question of any " specific " protective inocula- 

 tion or of any adaptation to a specifically iden- 

 tical material from the cultures, or of any 

 habituation to the presence of the same sort of 

 foreign protoplasm or to a similar poison. In 

 the course of various attempts made to bring 

 about the cure of bacterial diseases in this way 

 we gradually learned to see that the effects 

 produced depend upon the excitation of an in- 



