BACILLUS ANTHRAC1S AND ANTHRAX 783 



prostration. Death is the rule. The diagnosis is made by the dis- 

 covery of the bacilli in the feces. 



General hygienic prophylaxis against anthrax consists chiefly in 

 the destruction of infected animals, in the burying of cadavers, and 

 in the disinfection of stables, etc. The practical impossibility of 

 destroying the anthrax spores in infected pastures, etc., makes it 

 necessary to resort to prophylactic immunization of cattle and sheep. 



Immunity Against Anthrax. Minute quantities of virulent an- 

 thrax cultures usually suffice to produce death in susceptible animals. 

 Dead cultures are inefficient in calling forth any immunity in treated 

 subjects. It is necessary, therefore, for the production of active 

 immunity to resort to attenuated cultures. The safest way to, .accom- 

 plish such attenuation is the one originated by Pasteur, 18 consisting 

 in prolonged cultivation of the bacillus at 42 to 43 C. in broth. 

 Non-spore-forming races are thus evolved. 



The longer the bacilli are grown at the above temperature the 

 greater is the reduction in their virulence. Koch, Gaffky, and 

 Loeffler, 19 utilizing the variations in susceptibilities of different 

 species of animals, devised a method by means of which the relative 

 .attenuation of a given culture may be estimated and standardized. 

 Rabbits are less susceptible than guinea-pigs, and virulent anthrax 

 cultures, grown for two or three days after the stated conditions, 

 lose their power to kill rabbits, but are less virulent for guinea-pigs. 

 After ten to twenty days of further cultivation at 42 C. the virulence 

 for the guinea-pig disappears, but the culture is potent against the 

 still more susceptible mouse. Even the virulence for mice may be 

 entirely eliminated by further cultivation at this temperature. 



The method of active immunization first practiced by Pasteur, 

 and still used extensively, is carried out as follows: Two anthrax 

 cultures of varying degrees of attenuation are used as vaccins. The 

 premier vaccin is a culture which has lost its virulence for guinea-pigs 

 and rabbits, and is potent only against mice. The deuxieme vaccin 

 is a culture which is still definitely virulent for mice and guinea-pigs, 

 but not potent for rabbits. Forty-eight-hour broth cultures of these 

 strains, grown at 37.5 C., form the vaccin actually employed. Vaccin 

 I is subcutaneously injected into cattle in doses of 0.25 c.c., sheep 

 receiving about half this quantity. After twelve days have elapsed 

 similar quantities of Vaccin II are injected. 



18 Pasteur, loc. cit. 



19 Koch, Goffky, und Loeffler, Mitt. a. d. kais. Gesundheitsamt, 1884. 



