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 it 
