Swine Growers' Session. 101 



mentioned even produced a substance by purely chemical methods, 

 without the intervention of the bacteria which seemed to have 

 the same action as the substances isolated from the bacterial cul- 

 tures. Later events, however, demonstrated that none of these 

 substances could be depended upon to produce immunity in swine 

 against the natural disease. 



Following this, the investigations were directed toward the 

 production of an "immunizing or antitoxic serum" by the inocu- 

 lation of horses and cattle with gradually increasing doses of the 

 cultures of hog cholera and swine plague bacteria, somewhat in 

 the manner of the production of the "antitoxin," which is used so 

 successfully in human practice against diptheria. Extensive ex- 

 periments were made by Drs. De Schweinitz, Dorset and Niles of 

 the Bureau of Animal Industry and by Dr. Peters of the Nebraska 

 Experiment Station. The reports that were issued in regard to the 

 experimental work and practical tests indicated for a time that a 

 practical solution of the problem had been attained. But, unfor- 

 tunately this method in the end failed to meet the requirements.* 



The reason for the lack of success in the above mentioned ex- 

 periments is now very plain ; and is this : The Prime Cause of the 

 disease had not been discovered ; and the several investigators had 

 been working with bacteria which play only a secondary role in 

 producing the phenomena observed in hog cholera (and probably 

 swine plague).* 



The unsatisfactory results in attempting to produce immunity 

 by means of the bacteria mentioned, as well as other facts, in re- 

 gard to these bacteria, which were observed in the various investi- 

 gations, led to some doubt as to the so-called hog cholera germ be- 

 ing the true cause of the disease. It had early been observed that 

 the high degree of infectiousness of the disease, under natural con- 

 ditions, and the well marked virulence of the blood of diseased ani- 

 mals, was out of harmony with the low virulence of the germs which 

 had been isolated, and charged with being the cause of the disease. 

 But as these germs were so constantly associated with the disease 

 and were more virulent than any other forms that were occasion- 

 ally found, it was reasonable td regard these as the cause, and to 

 ascribe their low virulence to the unnatural conditions of their 



•In Germany, Wasserman and Osterag, working on the same line with the disease, 

 "Schweine seuche," which corresponds to the American swine plague, claim to have pro- 

 duced aprotective serum which is now in very large use In that country; being actively 

 promoted by a private commercial concern which manufactures it. The reports from dis- 

 interested veterinarians, however, indicate that this method has not proven an unquali- 

 fied success. The chances of success are more favorable in the case of the German switie 

 plague, since it Is not so frequently complicated with hog cholera. 



