258 SUSCEPTIBILITY AND IMMUNITY. 



which this pneumotoxine is destroyed if subsequently introduced, they 

 call " anti-pneumotoxine. " 



Emmorich, in a communication made at the recent (1891) Inter- 

 national Congress for Hygiene and Demography, in London, reports 

 results which correspond with those of G. and F. Klemperer so 

 far as the production of immunity is concerned, and also gives an 

 account of experiments made by Donissen in which the injection 

 of twenty to twenty-five cubic centimetres of blood or expressed 

 tissue juices, filtered through porcelain, from an immune rabbit into 

 an unprotected rabbit, subsequently to infection with a bouillon cul- 

 ture of " diplococcus pneumonise," prevented the development of 

 fatal septicaemia. Even when the injection was made twelve to fif- 

 teen hours after infection, by inhalation, the animal recovered. 



Emmerich and Mastraum had previously reported similar results 

 in experiments made upon mice with the Bacillus erysipelatos suis 

 (rothlauf bacillus). White mice are very susceptible to the patho- 

 genic action of this bacillus. But mice which, subsequently to in- 

 fection, were injected with the expressed and filtered tissue juices of 

 an immune rabbit, recovered, while the control animals succumbed. 

 According to Emmerich, the result in these experiments was due to 

 a destruction of the pathogenic bacilli in the bodies of the infected 

 animals ; and the statement is made that at the end of eight hours 

 after the injection of the expressed tissue juices all bacilli in the body 

 of the infected animal were dead. The same liquid did not, however, 

 kill the bacilli when added to cultures external to the body of an 

 animal. The inference, therefore, seems justified that the result de- 

 pends, not upon a substance present in the expressed juices of an 

 immune animal, but upon a substance formed in the body of the 

 animal into which these juices are injected. 



We have, however, an example of induced immunity in which 

 the result appears to depend directly upon the destruction of the 

 pathogenic microorganism in the body of the immune animal. In 

 guinea-pigs which have an acquired immunity against Vibrio Metsch- 

 nikovi the blood serum has been proved to possess decided germicidal 

 power for this " vibrio," whereas it multiplies readily in the blood 

 serum of non-immune guinea-pigs (Behring and Nissen). 



There is experimental evidence that animals may acquire an arti- 

 ficial immunity against the toxic action of certain toxalbumins from 

 other sources than bacterial cultures. Thus Sewell (1887) has shown 

 that a certain degree of tolerance to the action of rattlesnake venom 

 may be established by inoculating susceptible animals with small 

 doses of the " hemialbumose " to which it owes its toxic potency. 

 In this connection we may remark that there is some evidence to 

 show that persons who are repeatedly stung by certain poisonous 



