SPREAD OF THE DISEASE IN NATURE 313 



toxin. It killed animals susceptible to anthrax by a sort of 

 cachexia, and in suitably small doses could be used to immunise 

 them against subsequent inoculation with virulent bacilli. It 

 was chiefly retained within the bacilli when these were growing 

 in the most favourable conditions. Unlike the toxins of 

 tetanus and diphtheria, and unlike ferments, it was not 

 destroyed by heating to 110 C. The toxin produced by the 

 b. anthracis growing in a fluid medium remains intimately 

 associated with the bacterial protoplasm, as such cultures when 

 filtered are relatively non-toxic. 



It cannot be said that great light has been thrown on the 

 pathology of the disease by these researches. The effects of 

 infection by the b. anthracis are those shared by all other 

 organisms producing inflammation, the tendency to cedema 

 production of an unwonted degree being the chief special 

 feature and one with reference to which Martin's work may be 

 important. That toxic effects do occur in anthrax is undoubted, 

 for frequently, while the bacilli are still locally confined, there 

 may occur pyrexia and cedema spreading widely beyond the 

 pustule, but we have no definite information as to how these 

 effects are produced. In this disease we are probably dealing 

 with another example of the action of intracellular toxins, 

 regarding which, as in other cases, little is known. 



The Spread of the Disease in Nature. We have seen that 

 the b. anthracis rarely, if ever, forms spores in the body, and if 

 the bacilli could be confined to the blood and tissues of carcases 

 of animals dying of the disease, it is certain that anthrax in an 

 epidemic form would rarely occur. For it has been shown by 

 many observers that in the course of the putrefaction of such a 

 carcase the anthrax bacilli rapidly die out, and that after ten 

 days or a fortnight very few remain. But it must be remembered 

 that while still alive, an animal is shedding into the air by the 

 bloody excretions from the mouth, nose, and bowel, myriads of 

 bacilli which may rapidly spore, and thus arrive at a very re- 

 sistant stage. These lie on the surface of the ground and are 

 washed off by surface water. At certain seasons of the year the 

 temperature is, however, sufficiently high to permit of their 

 germination, and also of their multiplication, as they can un- 

 doubtedly grow on the organic matter which occurs in nature. 

 They can again form spores. It is in the condition of spores 

 that they are dangerous to susceptible animals. In the bacillary 

 stage, if swallowed, they will be killed by the acid gastric con- 

 tents; but as spores they can pass uninjured through the 

 stomach, and gaining an entrance into the intestine, infect its 



