A HISTORY OF SCIENCE 



tirely the formation of spores. The question being 

 put in this way, we are beginning to recognize that it 

 is capable of being solved. 



" We can, in fact, prevent the appearance of spores in 

 the artificial cultures of the anthrax parasite by vari- 

 ous artifices. At the lowest temperature at which this 

 parasite can be cultivated that is to say, about 4- 16 

 Centigrade the bacterium does not produce germs 

 at any rate, for a very long time. The shapes of the 

 minute microbe at this lowest limit of its develop- 

 ment are irregular, in the form of balls and pears in 

 a word, they are monstrosities but they are without 

 spores. In the last regard also it is the same at the 

 highest temperatures at which the parasite can be cul- 

 tivated, temperatures which vary slightly according 

 to the means employed. In neutral chicken bouillon 

 the bacteria cannot be cultivated above 45. Culture, 

 however, is easy and abundant at 42 to 43, but equal- 

 ly without any formation of spores. Consequently a 

 culture of mycelian bacteria can be kept entirely free 

 from germs while in contact with the open air at a tem- 

 perature of from 42 to 43 Centigrade. Now appear 

 the three remarkable results. After about one month 

 of waiting the culture dies that is to say, if put into 

 a fresh bouillon it becomes absolutely sterile. 



11 So much for the life and nutrition of this organism. 

 In respect to its virulence, it is an extraordinary fact 

 that it disappears entirely after eight days' culture at 

 42 to 43 Centigrade, or, at any rate, the cultures are 

 innocuous for the guinea-pig, the rabbit, and the sheep, 

 the three kinds of animals most apt to contract an- 

 thrax. We are thus able to obtain, not only the atten- 



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