§ XII.] Anthrax. 127 



Intestinal anthrax on the contrary is actually produced only 

 by the introduction of spores into the body, as has been proved 

 by Koch and his colleagues. In the natural course of things 

 the Bacillus can only reach the mucous membrane of the 

 intestine from the mouth, that is, when it is swallowed with 

 food. It has then to pass through the stomach, and here the rods 

 lose their efficiency, doubtless from the effects of the acid gastric 

 juice ; whether they are actually killed by it I am not prepared 

 to say. The spores, on the contrary, pass unaltered through 

 the stomach ; they find the conditions favourable to germination 

 in the contents of the intestine, and the rods developed in 

 germination make their way into the mucous membrane of 

 the intestine, especially through the lymph-follicles and Peyer's 

 patches; from there the way is open through the capillary 

 vessels in the mucous membrane to the passages of the 

 blood. 



It appears from the investigations of the above-named ob- 

 servers that animals which chew the cud are liable to be infected 

 in this way from the intestine. The experiments were made 

 with sheep. Experience also with horned cattle not purposely 

 infected seems to show by its agreement with these experiments 

 that the latter animals also are liable to this mode of infection. 

 It gives also the important practical result, that the cases of 

 anthrax which occur in them spontaneously, that is not inten- 

 tionally produced for experiments' sake, are chiefly of the 

 intestinal form, and are caused therefore by taking in the spores 

 of the Bacillus with the food. 



Other animals are less susceptible of infection from the intes- 

 tine; yet some attempts made to procure it succeeded in the 

 case of guinea-pigs, rabbits, and mice ; they were all unsuccessful 

 with rats, fowls, and pigeons. 



After all these experiences the first question is, whence do 

 the spores come from which enter the animal ? They are not 

 formed either in the living animal or in the unopened carcase, 

 for there vegetative development only takes place. But it was 



