204 LOUIS PASTEUR 



from rabid dogs was found to cause the death of 

 rabbits in about two days. A micro-organism was 

 observed in the blood of these rabbits, and it was 

 found that it could be cultured in veal broth and 

 that the cultures, when injected into other rabbits, 

 would cause their death. Pasteur was too cautious 

 to jump to the conclusion that he had found the 

 germ of hydrophobia. The incubation period, or 

 period between the first inoculation and the devel- 

 opment of symptoms of hydrophobia, is a relatively 

 long one, varying from about two weeks to, in some 

 cases, several months. It was more probable, 

 therefore, that the rabbits died from the effects of 

 some organism associated with the saliva of rabid 

 animals instead of the germ of hydrophobia, a sup- 

 position which was confirmed by inoculating rab- 

 bits with saliva from human beings with other dis- 

 eases and also with saliva from healthy persons. 

 This commonly proved fatal to rabbits. Saliva, 

 even in a healthy person, contains a multitude of 

 different kinds of bacteria as may readily be seen 

 by examining a drop of it under a microscope. 

 Some of these while harmless in our own mouths 

 are deadly when they gain access to the blood of 

 rabbits or guinea pigs. Consequently efforts to 

 induce rabies by the inoculation of saliva from 



