sato, Tizzoni and Cattani, G. and F. Klemperer, and others, including my own.
Ogata and Jasuhara, in a series of experiments made in the Hygienic Institute at Tokio (1890), discovered the important fact that the blood of an animal immune against anthrax contains some substance which neutralizes the toxic products of the anthrax bacillus. When cultures were made in the blood of dogs, frogs, or of white rats, which animals have a natural immunity against anthrax, they were found not to kill mice inoculated with them. Further experiments showed that mice inoculated with virulent anthrax cultures did not succumb to anthrax septicæmia if they received at the same time a subcutaneous injection of a small quantity of the blood of an immune animal. So small a dose as one drop of frog's blood, or one half drop of dog's blood, proved to be sufficient to protect a mouse from the fatal effect of an anthrax inoculation. And the protective inoculation was effective when made as long as seventy-two hours before, or five hours after, infection with an anthrax culture. Further, it was found that mice which had survived anthrax infection as a result of this treatment were immune at a later date (after several weeks) when inoculated with a virulent culture of the anthrax bacillus. Bearing and Kitasato have obtained similar results in their experiments upon tetanus and diphtheria, and have shown that the blood of an immune animal, added to virulent cultures before inoculation into susceptible animals, neutralizes the pathogenic power of these cultures. Tizzoni and Cattani ascribe the protection of animals which have acquired an immunity against tetanus to the presence of an albuminous substance which they call the tetanus antitoxine. This they have isolated from the blood of immune animals; and have shown by experiment that it neutralizes the potent toxalbumin of tetanus in test-tube cultures as well as in the bodies of infected animals. G. and F. Klemperer have recently (1891) published an important memoir in which they give an account of their researches relating to the question of immunity, etc., in animals subject to the form of septicaemia produced by the Micrococcus pneumoniæ crouposæ. They were able to produce immunity in susceptible animals by introducing into their bodies filtered cultures of this micrococcus, and proved by experiment that this immunity had a duration of at least six months. They arrive at the conclusion that the immunity induced by injecting filtered cultures is not directly due to the toxic substances present in these cultures, but that they cause the production in the tissues of an antitoxine which has the power of neutralizing their pathogenic action. Emmerich, in a communication made at the recent (1891) International Congress for Hygiene and Demography, in London, reports results which cor-
