INFECTIOUS DISEASES OF CATTLE. 467 



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

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

 hexe be cited. The characteristic tumor with its crackling sound 

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

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

 tissue under the skin is infiltrated with blood and yellowish, jeliylike 

 material and gas bubbles. The muscular tissue beneath the swelling 

 may 1)6 brownish or black, shading into dark red. (PL XLIV.) 

 It is soft and easily torn and broken up. The muscle tissue is dis- 

 tended with numerous smaller or larger gas-filled cavities, often to 

 such an extent as to produce a resemblance to lung tissue. Upon 

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

 connected with each other. 



In the abdomen and the thorax bloodstained fluid is not infre- 

 quently found, together with bloodstaining of the lining membrane 

 of these cavitias. Blood spotvS (or ecchymoses) are also found on 

 the heart and lungs. The liver is congested, but the spleen is always 

 normal. 



DifferenliaZ diagnosis. — Among the features of this disease which 

 distinguish it from anthrax may be mentioned the unchanged spleen 

 and the ready clotting of the blood. It will be remembered that in 

 anthrax the spleen (milt) is veiy much enlarged, the blood tarry, 

 coagulating feebly. The anthrax carbuncles and swellings differ from 

 the blackleg swellings in not containing gas, in being hard and solid, 

 and in causing death less rapidly. 



It is difficult to distinguish between the swellings of blacldeg and 

 malignant edema, since they resemble each other very closely and 

 both are distended with gas. Malignant edema, however, generally 

 starts from a wound of considerable size ; it usually follows surgical 

 operations, and does not resvdt from the small abrasions and pricks 

 to which animals are subjected in pastures. Inoculation experiments 

 on guinea pigs, rabbits, and chickens will also disclose the differences 

 between the above three diseases, since all of these species are killed 

 by the germ of malignant edema, only the first two species by the 

 anthrax bacillus, while the guinea pigs alone will succumb to the 

 blackleg infection. Hemorrhagic septicemia may be differentiated 

 from blackleg by its affecting cattle of all ages, by the location of the 

 swelling usually about the region of the throat, neck, and dewlap, 

 by the soft, doughy character of these swellings without the presence 

 of gas bubbles, and finally by the characteristic hemorrhages widely 

 distributed throughout the body. Other means of diagnosis, which 

 have reference to the specific bacilli, to the inoculable character of the 

 virus upon small animals, and which are of decisive and final impor- 

 tance, can be utilized only by the trained bacteriologist and veteri- 



