Black Leg 105 



teria do not enter the body in the feed or air. The 

 period of incubation of the disease is not known, but it is 

 supposed to be very short. The symptoms resemble 

 quite closely those of anthrax. The animal has a fever 

 and suffers loss of appetite and rumination. Tumors or 

 carbuncles may appear on the surface of the body, es- 

 pecially on the thighs and shoulders, but not below the 

 knee or hock joints or on the tail. The swelling is at first 

 small and painful. Later it increases in size, and be- 

 comes cold and painless, owing to the death of the tis- 

 sue. When the hand is passed over the swelling, gas can 

 be noted in the tissue, making a crackling sound under 

 pressure. When opened a dark frothy liquid exudes 

 which has a disagreeable odor. The disease is usually 

 fatal. The period of illness one to three days. 



Post-mortem examination. In a post-mortem exam- 

 ination the muscles about the tumors appear dark in 

 color, hence the name "black leg." The muscle fibres 

 of the tissue affected by the carbuncle are forced apart 

 by the gas. The production of gas in the body continues 

 after death, producing a bloated condition of the car- 

 cass. The tumors are much like those found in anthrax, 

 except that in anthrax tumors no gas is present. 



The blood in black leg is normal in color and in coagu- 

 lating properties, the spleen is not enlarged. These 

 often enable it to be distinguished from anthrax. 



General precautions. The organism causing black 

 leg is an anaerobic one. It produces spores in the car- 

 cass of the dead animal, even when unopened, as oxygen 

 is not necessary for spore formation. If the body is 

 opened and the soil polluted by blood, the organisms will 

 persist for a long time in the field. The same care 

 should be taken as in anthrax in making a post-mortem 



