7S2 MICROBIOLOGY OF DISEASES OF MAN AND DOMESTIC ANIMALS 



and others have shown that the serum of white rats contains a lysin 

 capable of dissolving the bacterium in vitro. Pigs are occasionally 

 infected; the carnivora generally are refractory, the bear and cat 

 being less resistant. Most birds are insusceptible, but some small 

 birds, like the sparrow, are more susceptible. Cold-blooded animals 

 are refractory. 



Infection occurs: Through the food, giving rise to intestinal anthrax. 

 Cattle and sheep are usually infected in this manner by spores, the bac- 

 terium being destroyed by the gastric juice. In man infection through 

 food rarely occurs. 



Through the air. Infection by inhalation through the lungs occurs 

 in man through the mediuin of dust contaminated by anthrax spores, 

 hence the name "wool-,sorter's disease. 



Through wounds. This method usually occurs in man and also in 

 sheep. Cutaneous infection comes through a scratch or wound, and 

 ^ves rise to a carbuncle — hence the name "malignant pustule." It 

 occurs most, frequently among employees of tanneries, wool-sorters, 

 veterinary surgeons, and those whose occupation brings them into 

 touch with infected animals, their hides or products. 



The incubation period is a short one, even in the naturally occurring 

 disease; inoculated laboratory animals die in twenty-four to forty- 

 eight hours. The bacteria appear in the blood about fifteen hours 

 after inoculation, and at death the blood simply swarms with the or- 

 ganism. The veins are turgid, and the blood is often very dark, and 

 coagulates slowly. The bacteria abound in the capillaries (Fig. 

 158). The spleen is enlarged and contains enormous numbers of the 

 organisms. In the kidney the glomeruli and tubules are gorged 

 with the bacteria, which pass into the urine. The bacteria can pass 

 into the milk of females in lactation. The bacteria are also numerous 

 in the liver, lungs and mesentery, but few are found in the muscles. 



Post-mortem examination of subcutaneously inoculated laboratory 

 animals shows subcutaneous oedema and enlarged spleen. 



The organism is eliminated from the body in urine, faeces, mucous 

 discharges, etc. Pastures become infected from burying anthrax 

 carcasses which have been opened or have been skinned, thus favoring 

 the formation of spores. If buried too near the surface, the rise of 

 the ground water, or the castings of earth worms, bring spores to 

 the surface and on to the herbage, where they may be ingested by graz- 



