Pathogenesis 601 



Pathogenesis. The disease is particularly fatal to 

 young pigs. The symptoms are not very characteristic, 

 and the animals often die suddenly without having appeared 

 very ill, or after seeming ill but a few hours. The chief 

 symptoms consist of fever (io6-io7 F.), unwillingness to 

 move about, and more or less loss of appetite. The animals 

 may appear stupid and dull, and have a tendency to hide 

 in the bedding and remain covered by it. The bowels may 

 be normal or constipated at the beginning of the attack, 

 but later there is a liquid and fetid diarrhea, abundant, 

 exhausting, and persisting to the end. The eyes are con- 

 gested and watery, the secretion drying and gluing the 

 lids together. The breathing is rapid, and there may be 

 cough. Occasionally one sees an eruption with crusts or 

 scabs of various sizes on the skin, which is often congested. 

 The animal becomes weak, stands with arched back and 

 drawn abdomen, and walks with a weak, tottering gait. 



The course of this disease varies from one or two days to 

 two or three weeks. 



At post-mortem examination petechiae, ecchymoses, and 

 extravasations of blood into the tissues are found to be com- 

 mon and characteristic of the acute form of the disease. 

 The spleen is enlarged to several times its normal size, and 

 is soft and engorged with blood. 



The extravasations of blood are common in the lymphatic 

 glands, beneath the serous membranes of the thorax and 

 abdomen, and particularly along the intestines ; on the sur- 

 face of the lungs and kidneys and in their substance. The 

 contents of the intestine are sometimes covered with clotted 

 blood. In the subacute form of the disease the principal 

 changes are found in the large intestine, and consist of ulcers 

 which appear as circular, slightly projecting masses varying 

 in color from yellow to black. Occasionally these ulcers 

 are slightly depressed. 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. 



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

 to be upon the intestines, with secondary invasion of the 

 lungs. 



The most characteristic lesions of the disease are the 

 petechiae and ecchymoses, the ulcerations of the large intes- 



