INFECTIOUS DISEASES OP CATTLE. 449' 



charged. The animal 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 postmortem changes may 

 here be cited. The characteristic tumor with its crackling sound 

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

 auimal it be more thoroughly examined, it will be noted that the tissue 

 under the skin is infiltrated with blood and yellowish, jelly-like mate- 

 rial and gas bubbles. The muscular tissue beneath the swelling may 

 be brownish or black, shading into dark red. (PI. XLIV. ) It is sof t- 

 and easily torn and broken up. The muscle tissue is distended 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 blood-stained fluid is not infre- 

 quently found, together with blood-staining of the lining membrane of 

 . these cavities. Blood spots (or ecchymoses) are also found on the hearfc- 

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



Differential 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 very much enlarged, the blood tarry,, 

 coagulating feebly. The anthrax carbuncles and swellings differ front 

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

 and in causing death less rapidly. 



It is difficult to distinguish between the swellings of blackleg 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 result from the small abrasions and pricks- 

 to which animals are subjected in pastures. Inoculation experiments-- 

 of 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- segtieemia 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 dis- 

 tributed 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- 

 narian. 



61386—08 29 



