XL] BACILLUS: PATHOGENIC FORMS. 161 



dents. 1 From all this it follows that as regards virulence the 

 bacilli anthracis differ in the different species of animals, and 

 in them acquire different qualities. A culture that does not 

 kill mice, such as an artificial culture of blood-bacillus after 

 one or two weeks' incubation at 20 to 35 C., or a culture 

 that for other reasons, as when attenuated by heat or anti- 

 septics, does not produce fatal anthrax in guinea-pigs, fails 

 to give to these animals any immunity whatever. Rodents, 

 so far as my experience goes, either die of inoculation with 

 anthrax-bacilli or they do not die ; but they are not 

 provided with immunity by the attenuated virus. 



Koch 2 maintains that in neutral chicken-broth the bacilli 

 growing at 42 C. lose their virulence in thirty days, and at 

 43 C. in six days, first for rabbits, then for guinea-pigs, and 

 lastly for mice. I am quite sure from my own observations, 

 that these results are not uniformly obtained, since I have 

 seen anthrax-bacilli very virulent both for rabbits and 

 guinea-pigs even after growing for thirty-six days at 42 '5 C. 



Bacillus anthracis is capable, as we have seen, of growing 

 well outside the body, and, when well supplied with oxygen 

 from the air, of forming spores which represent the per- 

 manent seeds. Thus if animals, such as sheep and cattle, 

 die of anthrax in a field, the bacilli in the effusions of 

 such animals (e.g. urine, blood, effluvia from the mouth and 

 nostrils) always contain numbers of the bacilli, and these will 

 be able to grow indefinitely on the surface of the soil, there 

 being always present a large amount of suitable nourishing 



1 Klein, Reports of the Medical Officer of the Local Government Board, 

 1882. Similar results have been obtained by Gaft'ky (Mittheil. a. d. k. 

 Gesundheitsamte, 1882). 



2 Ueber d. Milzbrandimpfung, 1882. 



Spores of bacillus anthracis stand heating to 100 C. in the dry state 

 for over an hour without being killed ; in the moist state, e.g. exposed 

 to steam at 100 C., they are killed after fifteen minutes' exposure 

 (Koch). 



M 



