Lesions Immunity 565 



to sixty hours after inoculation, they remain sitting in the 

 same characteristic position. 



When the ears of rabbits are inoculated, an inflamma- 

 tory edema and distinct redness, much resembling erysip- 

 elas, occur. This lesion gradually spreads, involving the 

 head and body of the animal, which ultimately dies. 



When swine are affected, they become dull and weak, 

 especially in the hind quarters; the temperature becomes 

 elevated, and red patches appear upon the skin, which 

 swells and becomes tender. Death follows in two or three 

 days. Sixty per cent, of the diseased animals die. 



Lesions. In all animals the anatomic changes are much 

 alike. The disease is a true bacteremia, and the bacilli can 

 be found in the blood and in all the organs, especially the 

 lungs and spleen. They are few in number in the streaming 

 blood. 



As the organisms stain well by Gram's method, this stain 

 is of great value for their discovery in the tissues, and can be 

 highly recommended. 



The bacilli chiefly occupy the capillary blood-vessels, 

 many of them being inclosed in leukocytes. The organs do 

 not appear distinctly abnormal, except the spleen, which 

 is enlarged. The mesenteric and other lymphatic nodes 

 are also enlarged, and the gastric and intestinal mucous 

 membranes are inflamed and mottled. The bacilli are also 

 found in the intestinal contents, and Kitt, who discovered 

 it, points out that the infection of swine probably takes 

 place through the ingestion of the fecal matter of diseased 

 animals. 



Immunity. Pasteur, Chamberland, Roux, and others 

 have worked upon protective vaccinations based upon the 

 attenuation of the virulence of the organism by passage 

 through rabbits. Two vaccinations are said to be sufficient 

 to produce immunity. The vaccinated animals, however, 

 may be a source of infection to others, and should always 

 be isolated. Klemperer in 1892 found that the blood-serum 

 of immunized rabbits would save infected mice into which 

 it was injected. 



Lorenz in 1894 found an antitoxic substance in the blood 



of rabbits immunized against the disease. Its injection 



into other animals, however, affords only a temporary 



immunity. Later * he found it possible to protect hogs 



* "Centralbl. f. Bakt. u. Parasitenk.," Jan., 1896, p. 168. 



