372 BACTERIA. 



of the anthrax could be modified was communicated in this 

 country by Greenfield, on June 17, 1880, to the Royal Society 

 of London. This observer found that by cultivating anthrax 

 bacilli through several successive generations, in flui.d taken 

 from the front part of the eye of the ox, he was able to 

 obtain a virus so modified that when injected into animals 

 susceptible of being affected by ordinary anthrax, the 

 animals did not die, whilst in animals injected with aqueous 

 humour cultures of the twelfth generation no symptoms 

 whatever were developed ; earlier cultures giving rise to a 

 modified form of anthrax only. 



In the following month Toussaint intimated to the French 

 Academy that he had been able to obtain a protective 

 anthrax vaccinal fluid, z.e., one that might be inoculated 

 into an animal without causing death, and which conferred 

 on animals so inoculated protection against a second attack 

 of the disease. 



His original method of procedure was as follows : — The blood of an 

 animal dead of anthrax was carefully defibrinated by whipping and straining 

 through linen and then through ten or twelve thicknesses of blotting-paper. 

 Some animals were undoubtedly protected by the inoculation of this pre- 

 pared blood, but the method was very uncertain ; and in some cases 

 the vaccine itself caused the death of the animal. Instead, therefore, of 

 filtering the defibrinated blood, he heated it for ten minutes to a temperature 

 of 55° C. With material so prepared he was able, by inoculation, to render 

 an animal immune to the action of the more virulent anthrax bacillus. 



Pasteur, who concluded that the vaccination depended not 

 on the bacterial products but on an alteration in the viru- 

 lence of the bacillus which might be the result of the altered 

 temperature, subjected the bacilli to a temperature of from 

 42° to 43° C. ; these were found to have lost all their vitality at 

 the end of about six weeks, this loss of vitality during the six 

 weeks going on progressively in proportion to the rise of 

 temperature. It is stated that at the outset the pure 

 culture had all the virulence of anthrax blood ; whilst 

 only half of the sheep inoculated with the culture, that 

 had been heated for twelve days succumbed to anthrax. 

 On the twenty-fourth day of heating, the culture, when 

 inoculated, although giving rise to mild febrile disturbance, 

 did not cause the death of a single animal. It was found, 

 too, that if now, twelve days after the first inoculation, these 

 surviving animals were inoculated with a culture from the 



