200 LOUIS PASTEUR. 



the method of successive cultivations in an artificial 

 medium. These cultivations, however, of the septic 

 vibrio require very special precautions and conditions. 

 They should be carried on in as perfect a vacuum as 

 it is possible to obtain, or in contact with carbonic 

 acid gas without the presence of air. In contact 

 with air the cultivations of septic vibrios would prove 

 sterile, because the vibrio is exclusively anaerobic and 

 air kills it. If a spore of this organism could germi- 

 nate in contact with the air, the product of the germina- 

 tion would be at once arrested and would perish by 

 the action of the oxygen. It is exactly the contrary 

 with the bacilli of splenic fever, which prove sterile in 

 a vacuum or in presence of carbonic acid gas. If one 

 of the spores of the splenic fever bacillus (for it also 

 produces spores) could germinate, die product of the 

 germination, deprived of free oxygen, would at once 

 perish. And, to mention in passing a very ingenious 

 experiment of Pasteur's, we thus obtain a means of 

 separating by culture the bacillus of splenic fever 

 from the septic vibrio when they are temporarily 

 associated together. If this mixture of pathogenic 

 organisms is cultivated in contact with the air, the 

 bacilli of splenic fever alone will be developed. If this 

 same mixture is cultivated without air, either in a 

 vacuum or in carbonic acid gas, the septic vibrio 

 alone will be developed. This device of culture is one of 

 the best which can be employed to demonstrate that the 



