284 SPECIFIC MICRO-ORGANISMS 



however, either because of lowered virulence of the germ Or of 

 increased resistance of the host, and in these cases the bacteria, 

 may be very scarce and difficult to find microscopically, even 

 after death of the animal. Cultures from the spleen will usually 

 show the presence of the bacillus there. The mechanism by 

 which the bacillus causes dea.th is unknown. In the acute cases, 

 as in the mouse, the bacilli are so abundant in the blood that 

 mechanical interference with the circulation seems a plausible 

 explanation, but this certainly does not suffice for other types of 

 the disease in which chemical poisoning must play the chief 

 r61e. So far it has not been possible to demonstrate any powerful 

 poisons in cultures of the anthrax bacillus. It is probable that 

 the essential poisons are produced by a reaction between the 

 substance of the bacillus and the fluids of the host, particularly 

 the enzymes of the latter, which cause disintegration of the bac- 

 terial bodies. 



The infection is acquired by grazing animals through the 

 alimentary tract primarily, but also to some extent by inoculation 

 (contact, flies, intermediate objects). In man there are three 

 recognized types (a) malignant pustule, (&) pulmonary anthrax, 

 and (c) intestinal anthrax. Malignant pustule results from in- 

 oculation of the skin, especially in those who handle hides or care 

 for anthrax animals. It is at first a local pustular and necrotic 

 lesion tending to involve contigious tissue by extension, but soon 

 invading the lymph vessels and walls of the veins. The bacteria 

 thus gain the blood stream and a rapidly fatal general ba^cteremia 

 supervenes. Recovery sometimes occurs before the disease be- 

 comes generalized. Several instances of malignant pustule of 

 the face were observed in soldiers in 1918, the infection being 

 derived from shaving brushes, in some of which anthrax bacilli 

 were found. Pulmonary anthrax is caused by inhalation of an- 

 thrax spores (woolsorter's disease). Intestinal anthrax is un- 

 common in man but has occurred. Both are very fatal forms of 

 the disease. 



Immunity to anthrax was first successfully produced by Pas- 



