BACILLI OF HEMORRHAGIC SEPTICEMIA GROUP 553 



genie for rabbits, less so for hogs, sheep, and horses, if infection is prac- 

 ticed by subcutaneous inoculation. Infection by ingestion does not 

 seem to cause disease in these animals. 



Historically, the bacillus of chicken cholera is extremely interesting, 

 since it was with this microorganism that Pasteur ' carried out some of 

 his fundamental researches upon immunity, and succeeded in immu- 

 nizing chickens with attenuated cultures. The first attenuation ex- 

 periment made by Pasteur consisted in allowing the bacilli to remain in 

 a broth culture for a prolonged period without transplantation. With 

 minute doses of such a culture (vaccin I) he inoculated chickens, fol- 

 lowing this, after ten days, with a small dose of a fully virulent culture. 

 Although enormously important in principle, the practical results from 

 this method, as applied to chicken cholera, have not been satisfactory. 

 It was with this bacillus, furthermore, that Pasteur was first able to 

 demonstrate the existence of a free toxin which could be separated 

 from the bacteria by filtration. 



BACILLUS OF SWINE PLAGUE 



{Bacillus suisepticus, Schweineseiiche) 



This microorganism is almost identical in form and cultural charac- 

 teristics with the bacillus of chicken cholera. It is non-motile, forms 

 no spores, is Gram-negative, and does not liquefy gelatin. The bacillus 

 causes an epidemic disease among hogs, which is characterized almost 

 regularly by a bronchopneumonia followed by general septicemia. 

 There is often a sero-sanguineous pleural exudate, a swelling of bronchial 

 lymph glands and of liver and spleen. The gastrointestinal tract is 

 rarely affected. The bacilli at autopsy may be found in the lungs, 

 in the exudates, in the liver and spleen, and in the blood. The disease 

 is rarely acute, but, in young pigs, almost uniformly fatal. 



It is probable that spontaneous infection usually occurs by inhala- 

 tion. Experimental inoculation is successful in pigs, both when given 

 subcutaneously and when administered by the inhalation method. 

 Mice, guinea-pigs, and rabbits are also susceptible, dying within three 

 or four days after subcutaneous inoculation of small doses. 



Active and passive immunization of animals against Bacillus suisep- 

 ticus has been attempted by various observers. Active immunization, 

 if carried out with care, may be successfully done in the laboratory. 



1 Pasteur, loc. cit. 



