SYSTEMATIC AND DESCRIPTIVE. 289 



monary mucous membranes are also regarded as 

 pathways of infection. In animals the disease is 

 known as " splenic fever." 



In man the mode of infection is by inhalation of 

 spores, and ingress by the pulmonary or intestinal 

 mucous membrane, or by direct inoculation of a 

 wound or abrasion. The spores are derived from 

 the wool or hides of animals which have died of 

 anthrax, and the resulting disease is known as 

 4 * wool- sorter's disease," and " pustula maligna." 

 Bacilli are found in the serum of the pustule, and in 

 sputum, urine, faeces, and sweat ; and if the disease 

 prove fatal, in the capillaries throughout the body. 



Attenuation of the virus. By cultivating the 

 bacillus in neutralised bouillon at 42 43 C. for 

 about twenty days, the infecting power is weakened, 

 and animals inoculated with it {premier vacciri) are 

 protected against the disease.* To obtain a still 

 more perfect immunity, they are inoculated a second 

 time with material (deuxieme vacciri) which has 

 been less weakened. The animals are then pro- 

 tected against the most virulent anthrax, but only 

 for a time. From such a culture, however, new 

 cultures of virulent bacilli can be started, and a 

 culture that is " vaccin " for sheep kills a guinea- 

 pig, and then yields bacilli that are fatal to sheep. f 

 Exposure to a temperature of 55 C., or treatment 

 with *5 to i per cent, carbolic acid, deprives the 



* Pasteur, Comfit. Rend., 1861, and Revue Scientifique, 1883. 

 t Klein, Micro-organisms and Disease. 1 885 . 



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