CIRCULATORY ORGANS 261 



ated. Later edematous swellings occur in the dependent parts of 

 the body. 



LEUKEMIA 



A few eases of leukemia have been observed in swine on postmortem 

 examination. The exact cause of disease is unknown, but it is prob- 

 ably of an infectious origin. 



Lesions. — Porcine leukemic cases thus far observed are of the lym- 

 phatic type. The lymph glands become enlarged, due to hyper- 

 plasia of the lymphoid tissue, and there are frequently necrotic cen- 

 ters. By scraping the cut surface of a lymph gland a milk-white 

 fluid is obtained. The spleen contains leukemic centers and is en- 

 larged, and the liver may be similarly affected. 



Fig. 66. Spleen of hog with a part of the gastrosplenic ligament and 

 cmentum. (Ostertag.) 



Cases of leukemia have not been studied clinicallJ^ The disease 

 is chronic in nature. 



Spleen 



The spleen is subject to hemorrhages and is engorged in hog 

 cholera and in other septicemic diseases. 



NECROSIS 



Necrosis of the spleen is of common occurrence in swine that have 

 died as a result of injection of a virus containing the Bacillus necro- 

 phorus. These centers vary in size from that of a dime to a fifty- 

 cent piece, are grayish-white in color, and usually have a raised 

 border and depressed center. There may be only one or two of, 

 these necrotic foci, or the spleen may be full of them. 



HYPERTROPHY 



Hypertrophy of the spleen is rather common. The condition occurs 

 in leukemia, tumor formation, and in swine that are fed excessively 

 and in paratyphoid infection. 



