respond 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 culture of "Diplococcus pneumoniæ" prevented the development of fatal septicaemia. Even when the injection was made twelve to fifteen 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 pathogenic action of this bacillus. But mice which, subsequently to infection, received by injection 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 injected 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 depends, 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 micro-organism in the body of the immune animal. In guinea-pigs, which have an acquired immunity against Vibrio Metschnikovi, 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.)
The antitoxines thus far referred to are from animals which have an acquired immunity against virulent cultures of wellknown pathogenic bacteria. But we have also experimental evidence showing the presence of antitoxines in animals immune against rabies and against vaccinia, two infectious diseases in which the specific infectious agent has not been demonstrated. Prof. Tizzoni, and his associate, Dr. Schwarz, have recently (1892) published the results of their experiments relating to the presence of an antitoxine in the blood of rabbits which have an acquired immunity against rabies. And I have shown by experiments made during the past two months that the blood of vaccinated and consequently immune calves contains an antitoxine which neutralizes the specific virulence of vaccine virus, both
