214 LOUIS PASTEUR. 



microbe here described belongs to a totally different 

 group from that of the vibrios. It is ranged under the 

 genus called ' micrococci.' ' It is in this group,' said 

 Pasteur on one occasion, ' that the microbes of the 

 viruses which are yet unknown will probably be one 

 day found.' 



In the cultivation of the microbe of fowl cholera, 

 Pasteur tried one of the cultivating liquids which he 

 had previously made use of with most success the 

 water of yeast that is to say, a decoction of yeast in 

 water rendered clear by filtration and then sterilised by 

 a temperature of over 100 degrees. The most diverse 

 microscopic organisms find in this liquid suitable 

 nourishment, particularly if it has been neutralised. 

 When, for example, the bacterium of splenic fever is 

 sown in the liquid, it assumes in a few hours a sur- 

 prising development. Now, it is remarkable that this 

 medium is quite unsuited to the life of the microbe of 

 fowl cholera. Not only does it not develop, but the 

 microbe perishes in this liquid in less than forty-eight 

 hours. May we not connect this singular fact with 

 that which is observed when a microscopic organism 

 proves innocuous in an animal which has been ino- 

 culated with it ? It is innocuous because it cannot 

 develop itself in the body of the animal, or because, 

 its development being arrested, it cannot attain the 

 vital organs. 



The decoction extracted from the muscles of the 



