HOG-CHOLERA. 415 



yellowish to black. Occasionally these ulcers are slightly 

 depressed in outline. When cut across they are found to 

 consist of a firm, solid growth extending nearly through 

 the intestinal wall. They are most frequent in the 

 cecum, upper half of the colon, and on the ileocecal 

 valve. In the chronic form of the disease the spleen is 

 rarely enlarged. 



u In hog-cholera the first effect of the disease is 

 believed to be upon the intestines, with secondary inva- 

 sion of the lungs." 



The most characteristic lesions of the disease are the 

 petechiae and ecchymoses, the ulcerations of the large 

 intestine (Fig. 113), and the collapse and occasional bron- 

 chopneumonic changes in the lung. 



The kidneys are nearly always affected, the urine con- 

 taining albumin and tube-casts. 



The specific bacillus of hog-cholera was secured by 

 Smith from the spleens of more than 500 hogs. It 

 occurs in all the organs and has also been cultivated 

 from the urine. 



The organisms appear as short rods with rounded 

 ends, 1.2-1.5 p. long and 0.6-0.7 P ^ n breadth. They are 

 very actively motile. No spore-production has ever been 

 observed. In general the bacillus resembles in appearance 

 that of typhoid fever. It stains readily by the ordinary 

 methods, but not by Gram's method. 



The bacilli possess numerous long flagella, easily 

 demonstrable by the usual methods of staining (Fig. 

 114). 



No trouble is experienced in cultivating the bacilli, 

 which grow well in all the media. 



Upon gelatin plates the colonies become visible in 

 twenty-four to forty-eight hours; the deeper ones spher- 

 ical with sharply defined borders. The surface is brown- 

 ish by reflected light, and is without markings. They 

 are rarely larger than 0.5 mm. in diameter and are homo- 

 geneous throughout. The superficial colonies have little 

 tendency to spread upon the gelatin. Their borders may 



