INFECTIOUS DISEASES 1 19 



The germ is motile and grows readily in the 

 laboratory on the different kinds of nutrient media, 

 especially in alkaline ones kept at the body tem- 

 perature. It grows in the presence or absence of 

 oxygen and does not form spores. It does not 

 liquefy gelatine or produce any specific odor. 



Accessory Causes. — The wide prevalence of this 

 disease can be acounted for by the unhygenic con- 

 ditions existing in the hog houses and their sur- 

 roundings. Filthy hog houses and yards are the 

 usual centers of infection in a community, and 

 when the germs become planted among such sur- 

 roundings they may live for several months and 

 remain active or virulent. 



Experiments conducted in order to determine 

 how the germs find their way into the body, show 

 that they usually enter by way of the digestive 

 tract, along with the food and water; hence un- 

 sanitary surroundings play an important part in 

 the spreading of the disease. Overcrowded hog 

 houses and muddy yards are favorable conditions 

 for infection. Feeding the hogs in the mud or on 

 filthy feeding floors, and watering them in dirty 

 troughs, or from ponds and streams, are common 

 sources of the disease. 



Hog cholera is frequently spread by exhibiting 

 hogs at stock shows and fairs where they may 

 have an oportunity to come in contact with the 

 germs of the disease in the pens, or when shipped 

 in stock or express cars. Buying hogs from dis- 

 eased herds is also a common source of contagion. 



