THE BACILLUS OF ANTHRAX. 



347 



are attenuated to such an extent that they will not kill a rabbit or a 

 sheep may still kill a guinea-pig ; or, if not, may kill a mouse. Pasteur 

 has shown that the pathogenic power of the bacillus may be reestab- 

 lished by inoculations into susceptible animals, and that an attenu- 

 ated culture which will not kill an adult guinea-pig may be fatal to 

 a very young animal of this species, and that cultures from the blood 

 of this will have an increased pathogenic virulence. 



Very minute quantities of a virulent culture are infallibly fatal to 

 these most susceptible animals, but for rabbits and other less sus- 

 ceptible animals the quantity injected influences the result, and re- 

 covery may occur after subcutaneous or intravenous injection of a 

 very small number of bacilli. 



FIG. 105. Bacillus anthracis in kidney of rabbit. X 400. (Baumgarten.) 



Infection in cattle and sheep commonly results from the ingestion 

 of spores while grazing in infected pastures. The bacillus itself, in 

 the absence of spores, is destroyed in the stomach. While spores are 

 not formed in the bodies of living animals, their discharges contain 

 the bacillus, and this is able to multiply in them and to form spores 

 upon the surface of the ground when temperature conditions are 

 favorable. It is probable that this is the usual way in which pastures 

 become infected, and that the bloody discharges from the bladder 

 and bowels of animals suffering from the disease furnish a nidus for 

 the external development of these reproductive elements ; as also do 

 the fluids escaping from the bodies of dead animals. And possibly, 

 under specially favorable conditions, the bacillus may lead a sapro- 

 phytic existence for a considerable time in the superficial layers of the 

 soil. 



