274 VETERINARY BACTERIOLOGY 



when inoculated with yV c.c. of a virulent bouillon culture. Guinea- 

 pigs are more refractory, and die after seven to twelve days. 

 Subcutaneous and intravenous injections and feeding experi- 

 ments rarely produce death in the hog. The animal may some- 

 times show fever and depression, particularly after the intravenous 

 inoculation, but the infection is rarely fatal unless 1 or 2 c.c. or 

 more of culture are used. Feeding with large quantities of culture 

 or long-continued feeding sometimes proves fatal. 



Character of Disease and Lesions Produced. An examination 

 of a rabbit killed by injections of B. cholerce suis shows lesions 

 differing in no material respect from those discussed under B. en- 

 teritidis. To just what extent the characteristic lesions in hog- 

 cholera, particularly in the chronic types, are due to infection 

 by this organism is uncertain. It is probable that in many cases, 

 at least, it is responsible for the development of intestinal ulcers. 

 Inasmuch as it is sometimes found in the blood of animals infected 

 by hog-cholera, it is probable that death may be due directly to 

 their activity. 



Immunity. The topic of immunity against hog-cholera will be 

 considered under that heading. The B. cholerce suis produces no 

 true toxin, but there is some evidence of the formation of endo- 

 toxin. Agglutinins are present normally in the blood of the hog, 

 and immune agglutinins may be produced by the systematic im- 

 munization of animals by killed cultures. Group agglutination 

 with other members of this subgroup has been demonstrated. It 

 has also been shown that immunization of the hog against true 

 hog-cholera results in a considerable increase of agglutinins for B. 

 cholerce suis in the blood. Opsonins for B. cholerce suis have been 

 shown to be'present in normal serum. Since the discovery of the 

 filterable virus, efforts at immunization by the use of vaccines and 

 sera prepared by the use of B. cholerce suis have been practically 

 abandoned. 



Bacillus paratyphosus 



Synonym. Paratyphoid or paracolon bacillus. 



Disease Produced. Paratyphoid in man, possibly similar 

 infections in animals. 



Gwyn, in 1898, isolated from a clinical typhoid case an organ- 

 ism which belonged to the intermediate subgroup of intestinal 



