304 SWINE PRACTICE 



is variable, and it seems plausible that some predisposing condition 

 must exist in the swine that become affected, or the organism sud- 

 denly, for some reason unexplained, becomes sufficiently virulent 

 to produce the disease. In most severe outbreaks it appears that the 

 virulent organisms are transmitted from the diseased to the suscep- 

 tible swine, or at least the disease may become enzootic in a very 

 short time, 



Channel of entrance. — The channel of entrance may be by way 

 of the respiratory organs, although the microorganism may be suc- 

 cessfully introduced through the digestive tract or skin. 



Lesions. — This disease assumes different types or forms. Tlie fol- 

 lowing types have been recognized: the septicemic, the pulmonary, 

 and the intestinal. It is not uncommon to find the pulmonary and 

 intestinal types existing at the same time. In other instances either 

 the pulmonary or intestinal type may represent the primary condi- 

 tion, and the septicemic type develop in the same animal, and usually 

 result fatally. 



The septicemic form is characterized by petechial hemorrhages in 

 the skin and in the serous and mucous membranes. There may alsn 

 be some enlargement of the lymph-nodes and of the spleen. The pul- 

 monary form of the disease is characterized by an atypical catarrhal 

 pneumonia, different areas of the lung showing different stages of 

 progress of the disease, such as congestion, red hepatization, gray 

 hepatization, and later necrosis, in which the necrotic material may 

 be liquid or caseous. As a result of the variation of the progress 

 of the disease in different areas, the affected lung has a marbled or 

 mottled appearance. There are some interlobular infiltrations; the 

 bronchial and mediastinal glands may contain hemorrhages or necrotic 

 centers; the pleura is usually affected with a fibrinous pleurisy witli 

 or without adhesions. In the more chronic cases the necrotic foci in 

 the lung become more numerous and there may be a purulent or 

 septic pleurisy, the discharge into the pleural cavity of the contents 

 of necrotic pulmonary centers. There will be a diffuse redness of 

 the skin. 



The intestinal form of the disease is usually manifested by hemor- 

 rhages and inflammation, the inflammatory process resulting in the 

 deposit of a sticky tenacious exudate, which may be uniformly dis- 

 tributed upon the mucosa of the large or small intestine, or it may 

 appear as scattered areas. The exudate adheres tenaciously to the 

 mucous membrane. The related lymph-glands are usually tumefied 



