226 DISEASES OF THE HOG. 



there was pleurisy with hydrothorax to a consider- 

 able extent, also considerable effusion of fluid in 

 the abdominal cavity. There are often indications 

 of heart derangement, such as effusions of fluid and 

 blood clots, and in chronic cases enlargement of 

 the walls of the heart. In swine plague the liver 

 is often found in a very deranged condition, of a 

 bluish gray color, soft and falling to pieces when 

 handled, especially in chronic cases. Hog cholera 

 has usually more intestinal lesions, and swine 

 plague more lung and liver affections. The hog 

 cholera germs are very vigorous and more hardy 

 than those of swine plague. They are capable of 

 multiplying and living for a long time in water, 

 ponds and streams; they may live in the earth and 

 rubbish for three months or more. Swine plague 

 germs, on the other hand, are much more delicate 

 and easily destroyed. In order that they will mul- 

 tiply and grow the temperature must be more con- 

 stant and the surrounding media more favorable 

 than is required for the germs of hog cholera. It 

 is said that the swine plague germs are widely dis- 

 tributed in nature and probably present in all 

 herds of swine, but they are not deadly to these ani- 

 mals except when their virulence has been in- 

 creased or the resistance of the animals dimin- 

 ished by some unusual conditions. The hog chol- 

 era germs, on the contrary, are not usually present 

 and must be introduced from infected herds before 

 the disease can be developed. This may or may not 

 be true, as it is impossible to find out the cause of 

 the beginning or end of a contagious disease. If ic 



