PLAGUE AND BACILLUS PESTIS 829 



chicken cholera, have not been satisfactory. It was with this bacil- 

 lus, 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, Schweineseuche) 



This microorganism is almost identical in form and cultural 

 characteristics 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 char- 

 acterized almost regularly by a bronchopneumonia followed by 

 general septicemia. There is often a sero-sanguineous pleura! 

 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 in- 

 halation. 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 

 suisepticus has been attempted by various observers. Active im- 

 munization, if carried out with care, may be successfully done in 

 the laboratory. Passive immunization of animals with the serum of 

 actively immunized horses has been practiced by Kitt and Mayr, 38 

 Schrieber, 39 and Wassermann and Ostertag. The last-named ob- 

 servers, working with a polyvalent serum produced with a number 

 of different strains of the bacillus, have obtained results of consider- 

 able practical value. The researches of Kitt and Mayr have revealed 

 a fact pointing to the interrelationship of the bacilli of the "hemor- 

 rhagic septicemia" group. They were able to show that the serum 

 of horses immunized with chicken cholera bacilli was able to protect, 

 somewhat, against Bacillus suisepticus. 



*Kitt and Mayr, Monatsschr. f. Thier Leilk., vol. 8, 1897. 

 39 Schrieber, Berl. Thierarztl. Wochenschr., vol. 10, 1899. 



