PROTECTIVE INOCULATION 1 47 



ially with brilliant lamp or gas light. These violet granules 

 differ a good deal in form and size ; sometimes they are very 

 minute, and at others coarsely granular. When the bacteria 

 are arranged in clumps the violet material is often in greatest 

 amount about them. Free-lying anthrax rods will be sur- 

 rounded by a thick envelope of the same substance. M' Fad- 

 yean states that he has never found this reaction in animals 

 dead from other diseases. The peculiar coloring, he states, 

 in some cases may be observed without the aid of the 

 microscope. 



§ 125. Protective inoculation. Toussaint was the first 

 to make use of protective inoculations in anthrax. He heated 

 defibrinated anthrax blood to a temperature of 50 to 55° C. for 

 from 15 to 20 minutes, then injected it as a protective agent. 

 Pasteur, however, was the first to prove that immunity could 

 be obtained by the use of cultures of attenuated bacteria. 

 Several methods of attenuating the specific organisms have 

 been proposed by Pasteur, Toussaint, Chaveau, Chamberland, 

 Arloing and others. 



Pasteur's method consists in inoculating the animal with 

 a small quantity of culture which has been grown at a high 

 temperature— 42 to 43° C— for several days. This deprives 

 the bacteria of their virulence. To strengthen the resistance, 

 the animals are again inoculated with a stronger virus. After 

 the two inoculations, they are said to be protected against the 

 most virulent anthrax ; but the immunity is of short duration. 

 Chamberland reported in 1894 that a total of 1,988,677 animals 

 had been treated by this method in France, and that the loss 

 from anthrax had diminished from 10 per cent in sheep and 5 

 per cent in cattle to less than i per cent. Cope, in his report 

 to the English Board of Agriculture, regards the conclusions 

 of Chamberland as somewhat fallacious, because in order to 

 prove that the animals inoculated received immunity, it should 

 be shown that they were subsequently exposed to the risks of 

 natural infection. The excellent work which has been done 

 by Neal and Chester, at the Delaware College Experiment 



