THE BACILLUS OF HOG CHOLERA 283 



From the experiments of Dorsett and his co-workers it became 

 evident that the Bacillus cholerse suis was not the true, principal, and 

 sole cause of hog cholera. Even before the papers of de Schweinitz 

 and Dorsett and his associates on the exact etiology of hog cholera 

 had been published, other investigators, such as Hottinger, working in 

 Brazil, Theiler, in South Africa, and also Boxmeyer had begun to 

 doubt the etiological importance of the Bacillus suipestifer. Hottinger 

 believed the bacillus to be an organism of the colon croup which 

 penetrated from the intestines into the general circulation, but which 

 was not the true cause of the disease. The experiments of Dorsett, 

 McBryde, Niles, and Bolton, of the United States Department of 

 Agriculture on the production of the disease by bacteria-free blood, 

 were confirmed by Theiler, Hutyra, Ostertag and Stadies, McClin- 

 tock, Boxmeyer and Siffer, Uhlenhut, Xylander and Bohtz, Wasser- 

 mann, Carre, Leclainche and Vallee, and others. There is at the 

 present time no doubt remaining that hog cholera is, indeed, due to a 

 filterable, invisible, ultramicroscopic, highly contagious living virus, 

 and not to the bacillus suipestifer. 



Protective Inoculation. The fact that animals which recover from 

 hog cholera are immune for the remainder of their natural lives was 

 noticed early in the modern studies of the disease. Such animals 

 could not even be made sick by injecting into them blood from cholera- 

 sick hogs. Since the discovery that the affection is due to an invisible 

 virus, Dorsett has worked out a method to hyperimmunize hogs, so 

 that their blood contains a large amount of antibodies and can be 

 used as an antitoxin or immune serum to protect non-immune animals 

 against a fatal or serious attack. The serum is prepared in a hog 

 which has survived a natural attack of the disease. The animal is 

 injected with very virulent blood from a cholera-sick hog, but it 

 must first be definitely ascertained by the injection of 2 to 5 c.c. 

 of the blood into two non-immune hogs, that it actually is virulent. 

 If the injected non-immunes do not become very sick themselves, 

 the blood tested is not of sufficient virulence, and the test must be 

 repeated until found satisfactory with virulent blood from another 

 source. The hyperimmunization of the immune hog is then brought 

 about in the following manner: 



1. Subcutaneous Injections. (a) Inject the immune subcutaneously 

 with defibrinated disease-producing blood in the proportion of 10 c.c. 

 for each pound of body weight; or (6) inject the immune subcutan- 

 eously with 1 c.c. of defibrinated disease-producing blood for each 

 pound of body weight. After an interval of one week give a second 

 injection of 2.5 c.c. disease-producing blood for each pound of body 

 weight. After the interval of another week give a third injection of 

 5 c.c. of disease-producing blood for each pound of body weight. 



2. Intravenous Injections. (a) Inject the immune intravenously 

 with defibrinated disease-producing blood in the proportion of 5 c.c. 

 of blood for each pound of body weight; or (6) inject the immune 



