100 Missouri Agricultural Report. 



discovered bacterium the name "Swine Plague" was applied. It 

 was found, however, that cultures of this microorganism from dif- 

 ferent sources were quite variable in their action when inoculated 

 into experiment animals. In some cases a rapidly fatal septicaemia, 

 "blood poisoning," was produced in rabbits; while in other cases 

 no serious illness resulted ; and especially were the effects on swine 

 doubtful when cultures of the germs were injected subcutaneously, 

 and the feeding of cultures, or even of the viscera of inoculated 

 rabbits proved negative. 



"Injection of the germs directly into the circulation is usually 

 fatal when virulent varieties are employed." "When the bacteria 

 are injected directly into the lung tissue through the chest wall 

 death may follow in 16 to 24 hours, or life may be prolonged and 

 a severe inflammation of the lungs may result." 



Following these investigations, efforts were directed towards 

 discovering effective means of immunizing swine against the dis- 

 eases mentioned: — 



Experiments were made to determine whether the bacteria 

 described could in any way be utilized as a vaccine against these 

 maladies. Success in this direction had been attained in other dis- 

 eases ; for instance, in "anthrax" and in "black-leg." Domesticated 

 rabbits, having shown a susceptibility to the pathogenic action of 

 the swine bacteria mentioned, these animals were used mainly in 

 the laboratory experiments, and it was found possible to produce 

 a considerable degree of resistance in these animals against the 

 "hog-cholera" and "swine-plague" bacteria, that had been cultivated 

 artificially, and the same was also true in the case of swine; but 

 when the hogs, which had been immunized against the bacteria 

 grown artificially in the laboratory, were exposed to natural out- 

 breaks of cholera they showed no great resistance to the disease; 

 and for practical ends these measures failed. 



The "toxins" or poisonous products produced by the bacteria 

 during their growth were next tried as immunizing agents. Dr. 

 Von Schweinitz separated from artificial cultures of the hog-cholera 

 bacillus, and the swine-plague bacterium, certain chemical sub- 

 stances (alkaloids and albuminoid products) some of which he 

 found to be poisonous, and with which he produced with graduated 

 doses a certain degree of resistance against the usually fatal doses, 

 that is, in small experimental animals — guinea pigs. Both he and 

 the Chief of the Bureau felt greatly encouraged, and were led to 

 think that in the use of these chemical substances a practical 

 method of preventing these diseases would be found. The chemist 



