BLACKLEG. 



461 



barbed wire, stubbles, thorns, briers, grass burs, and sharp or pointed 

 parts of feed. Infection by way of digestive tract is also probable. 



Symptoms and lesions.— The symptoms of blackleg may be either 

 of a general or of a local natui^, though more frequently of the 

 latter. The general symptoms are very muchjike those belonging 

 to other acute infectious or bacterial diseases. CThey begin, from one 

 to three days after the infection has taken place, with loss of appe- 

 tite and of rumination, with dullness and debility, and a high fever. 

 The temperature may rise to 107° F. To these may be added lame- 

 ness or stiffness of one or more limbs, due to the tumor or swelling 

 quite invariably accompanying the disease. After a period of dis- 

 ease lasting from one to three days the affected animal almost always 

 succumbs. Death is preceded by increasing weakness, difficult 

 breatliing, and occasional attacks of violent convulsions.^] 



The most important characteristic of this disease is the appear- 

 ance of a tumor or swelling under the skin a few hours after the 

 setting in of the constitutional symptoms described above. In some 

 cases it may appear first. This tumor may be on the thighs (hence 

 "blackleg," "black quarter"), the neck, the shoulder, the breast, 

 the flanks, or the rump ; never below the carpal (or knee) and the 

 hock joint. It more rarely appears in th« throat and at the base 

 of the tongue. The tumor, at first small and painful, spreads very 

 rapidly both in depth and extent. Wh^i it is stroked or handled 

 a peculiar crackling sound is heard under the skin; this is due to 

 a collection of gas formed by the bacilli as they multiply. At th^ 

 stage the skin becomes dry, parchment-like, and cool to the touch 

 in the center of the tumor. If the swelling is cut into, a frothy, 

 dark-red, rather disagreeable-smelling fluid is discharged. The ani- 

 mal manifests little or no pain during the operation. 



As it is frequently desirable to know whether the disease is anthrax 

 or blackleg, a few of the most obvious post-mortem dianges may 

 here be cited. The characteristic tumor with it-s crackling sound 

 when stroked has already been described. If after the death of the 

 animal it is more thoroughly examined, it will be noted that the 

 tissues under the skin are infiltrated with blood and yellowish, j^ly- 

 like material and gas bubbles. The muscular tissue beneath the 

 swelling may be brownish or black, shading into dark red. (PL 

 XLII.) It is soft, easily torn and broken up. TTae muscle tissue 

 is distended with numerous smaller or larger gas-filled cavities, 

 often to such extent as to produce a resemblance to lung tissue. 

 Upon incision it does not collapse perceptibly, as the gas cavities are 

 not connected with one another. 



In the abdomen and the thorax blood^ained fluid is not infre- 

 quently found, together with bloodstaining of the lining membrane 

 of these cavities. Blood spots (or ecchymoses) are also found on 



