246 VETERINARY BACTERIOLOGY 



the sparrow, and the pigeon are likewise susceptible. The typi- 

 cal disease may be produced in swine by inoculation of pure cul- 

 tures. There is no doubt but that the Bacillus rhusiopathice is 

 the cause of the disease. There is some evidence that the infec- 

 tion in a mild urticarial form is occasionally transmitted to the 

 human. 



Character of Disease and Lesions Produced. Small numbers of 

 bacteria can generally be demonstrated in the blood, and abun- 

 dantly in various of the body organs, particularly the spleen 

 and the lungs. In the acute type of the disease the mucous mem- 

 brane of the alimentary tract is reddened, and shows petechial 

 hemorrhages. The spleen and the lymph-nodes are somewhat 

 enlarged, and the lungs are usually congested. The most char- 

 acteristic lesions are those of the skin, where numerous congested 

 areas and local hemorrhages give rise to the spotted appear- 

 ance. In chronic cases there is generally a verrucose or ulcerous 

 endocarditis which is quite characteristic. 



Immunity. No true toxin has been demonstrated for the 

 Bacillus rhusiopathice. The presence of specific amboceptors in 

 immune serum may be shown by the method of complement 

 absorption, but just what part these play in immunity has not 

 been satisfactorily demonstrated. Opsonins are present, and prob- 

 ably account in part for the immunity. 



Very young animals under three months and those over 

 one year rarely contract the disease. Animals that recover from 

 the disease are thereafter immune. 



Active Immunization. It has been shown by the researches of 

 Pasteur, later by Kitt and others, that passage of strains through 

 certain animals, particularly the rabbit or the pigeon, leads to an 

 attenuation such that the material may be used for vaccination 

 of the hog. It is also known that continued cultivation usually 

 reduces the virulence of the organism for mice. The virulence 

 is subject to great and inexplicable variations. The Pasteur 

 vaccine consists of an attenuated bouillon culture of the B. rhusio- 

 pathice. The material is sent out in two packages, labeled Vaccine 

 I. and Vaccine II. These are injected fifteen days apart. Im- 

 munity is established in two to three weeks after the second injec- 

 tion. The injected animals sometimes show the characteristic 



