SUSCEPTIBILITY AND IMMUNITY. 257 



power. The blood of chickens, which have a natural immunity 

 against tetanus, was found not to have a similar power. Behring 

 and Kitasato have also shown that the serum of a diphtheria-immune 

 rabbit destroys the potent toxalbumin in diphtheria cultures. It 

 does not, however, possess any germicidal power against the diph- 

 theria bacillus. 



Ogata, in a recent publication (1891), reports that he has succeeded 

 in isolating from the blood of dogs and of chickens a substance to 

 which he ascribes the immunity of these animals from certain infec- 

 tious diseases, and the power of their blood to protect susceptible 

 animals from the same diseases. This substance is soluble in water 

 and in glycerin, but insoluble in alcohol or ether, by which it is pre- 

 cipitated without being destroyed. Its activity is neutralized by 

 acids, but not by weak alkaline solutions. Ogata supposes the sub- 

 stance isolated by him to be the active agent in blood serum by 

 which certain pathogenic bacteria are destroyed, as shown by the 

 experiments of Nuttall, Buchner, and others. Hankin had previously 

 isolated an albuminoid substance from the spleen and blood of the 

 rat, to which he ascribes the immunity of this animal from anthrax. 

 This substance, according to the author named, is a globulin ; it is 

 insoluble in alcohol and in distilled water, and does not dialyze. 



Tizzoni and Cattani ascribe the protection of animals which have 

 acquired an immunity against tetanus to the presence of an albu- 

 minous substance which they call the tetanus-antitoxine. This they 

 have isolated from the blood of immune animals. They arrive at 

 the conclusion that it is a globulin, or a substance which is carried 

 down with the globulin precipitate, and that it is different from the 

 globulin, above referred to, obtained by Hankin from animals im- 

 mune against anthrax. 



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 pneumonise crouposae. 

 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 in- 

 duced by injecting filtered cultures is not directly due to the toxic 

 substances present in these cultures, but that they cause the produc- 

 tion in the tissues of an antitoxine which has the power of neutraliz- 

 ing their pathogenic action. The toxic substance present in cultures 

 of the "diplococcus of pneumonia" they call " pneumotoxine "; the 

 substance produced in the body of an artificially immune animal, by 

 17 



