MICROBIAL DISEASES OF MAN AND ANIMALS. 635 



SYMPTOMATIC ANTHRAX OR BLACKLEG.* 

 Bacillus anthracis symptomatici. 



Blackleg, black quarter, symptomatic anthrax, quarter ill, are syno- 

 nyms employed to designate this disease. 



Symptomatic anthrax is a very old disease and until recent years has 

 been confused with true anthrax. This disease is widely distributed, 

 affecting practically all countries and climates. 



It is enzootic, never spreading widely or rapidly, and is often found 

 in certain infected valleys and in relatively small areas. Young cattle, 

 generally under two years of age, are most commonly affected, but sheep 

 and goats are susceptible to this infection. 



This disease is infectious by inoculation and usually acute. Sub- 

 cutaneous and muscular tissues are especially affected. Its most 

 prominent and characteristic feature is swelling of the front or hind 

 quarters, never extending below the knee or hock. As a rule, the bacillus 

 of symptomatic anthrax produces a very acute disease with high fever 

 and severe constitutional disturbances. 



The bacillus of symptomatic anthrax has been clearly demonstrated 

 to be the specific cause of blackleg, infection occurring by inoculation. 

 The period of incubation in the natural disease is uncertain. Under 

 artificial inoculation this period varies from two to three days and is 

 occasionally as short as one day. 



This bacillus produces in culture a very active toxin. This toxin 

 is quite resistant to heat. That the bacillus of symptomatic anthrax 

 stimulates the production of antibodies and that the injury is done by 

 toxins, is shown by the fact that immunity against virulent culture may 

 be produced by treatment with presumably sterile filtrates of virulent 

 cultures. 



An antitoxin has been produced which contains a body capable of 

 increasing the attraction by this bacillus for the leucocytes, thus protecting 

 the infected animal. 



The bacillus of symptomatic anthrax is rarely found in the blood 

 before death; but is abundant in the affected muscle and overlying sub- 

 cutaneous tissue. It also occurs in great numbers in the bile and intestinal 

 contents. 



Mucous membranes become congested and then very dark. Local 



* Prepared by M. H. Reynolds. 



