572 PATHOGENIC MICROORGANISMS 



mechanical means, such as capillary obstruction. Neither a true 

 secretory toxin nor an endotoxin has been demonstrated for the anthrax 

 bacillus. The decidedly toxemic clinical picture of the disease, however, 

 in some animals and in man, precludes our definitely concluding that 

 such poisons do not exist. It is a matter of fact, however, that neither 

 culture nitrates nor dead bacilli have any noticeable toxic effect upon 

 test animals, and exert no appreciable immunizing action. 



Spontaneous infection of animals takes place largely by way of the 

 alimentary canal, the bacilli being taken in with the food. The bacteria 

 are swallowed as spores, and therefore resist the acid gastric juice. In 

 the intestines they develop into the vegetative forms, increase, and 

 gradually invade the system. The large majority of cattle infections 

 are of this type. Direct subcutaneous infection may also occur sponta- 

 neously when small punctures and abrasions about the mouth are made 

 by the sharp spicules of the hay, straw, or other varieties of fodder. 



When infection upon a visible part occurs, there is formed a diffuse, 

 tense local swelling, not unlike a large carbuncle. The center of this may 

 be marked by a black, necrotic slough, or may contain a pustular de- 

 pression. 



Infection by inhalation is probably rare among animals. Trans- 

 mission among animals is usually by the agency of the excreta or un- 

 burned carcasses of infected animals. The bacilli escaping from the 

 body are deposited upon the earth together with animal and vegetable 

 matter, which forms a suitable medium for sporulation. The spores 

 may then remain in the immediate vicinity, or may be scattered by 

 rain and wind over considerable areas. The danger from buried car- 

 casses, at first suspected by Pasteur, is probably very slight, owing to the 

 fact that the bacilli can not sporulate in the anaerobic environment to 

 which the burying-process subjects them. The disease, in infected cattle 

 and sheep, is usually acute, killing within one or two days. The mortality 

 is extremely high, fluctuating about eighty per cent. 



In man the disease is usually acquired by cutaneous inoculation. It 

 may also occur by inhalation and through the alimentary tract. 



Cutaneous inoculation occurs usually through small abrasions or 

 scratches upon the skin in men who habitually handle live-stock, and 

 in butchers, or tanners of hides. Infection occurs most frequently upon 

 the hands and forearms. The primary lesion, often spoken of as " malig- 

 nant pustule," appears within twelve to twenty-four hours after inocula- 

 tion, and resembles, at first, an ordinary small furuncle. Soon, however, 

 its center will show a vesicle filled with sero-sanguineous, later sero- 



