GERMS OF DISEASE AND DEATH. 255 



these rod-like plants. But exact demonstration of 

 the truth of the latter statement can be had. 



If we grow and cultivate in a proper fluid such as 

 the aqueous humour of the eye of an ox the " rods," 

 we may inoculate with our "rods" the body of a 

 healthy animal. We may sow in that animal's body 

 the germs of splenic fever. Thus a drop of a solution 

 containing the ' c rods " sown within the body of a 

 guinea-pig, produces splenic fever in that animal. 

 And more wonderful still, it has been shown that the 

 dried blood taken from an animal affected with this 

 fever will reproduce the fever, even after an interval 

 of four years, if the dried particles of blood with their 

 "rods" be introduced into the body of a healthy animal. 



Pasteur, armed with knowledge of the kind just 

 detailed, set himself to ascertain the ' ' reason why " 

 splenic fever should suddenly appear in districts which 

 knew it not, and wherein only healthy animals lived. 

 Obviously, if the germ theory were true, such sudden 

 and apparently isolated outbreaks must be capable of 

 being explained on this hypothesis. The idea of the 

 " spontaneous," or de novo, or ex nihilo origin of the 

 disease would, if supported by facts, prove fatal to 

 the (C germ theory." Here, then, was a typical case 

 for scientific investigation. Let us see how the genius 

 of Pasteur overcame the difficulties of the situation. 



The localities in which splenic fever seemed to 

 burst out suddenly and without warning were, as 

 Pasteur learned, former seats of the disease. But the 

 interval between the visitation was to be measured 

 by years. How, then, could the new outbreak be 



