94 INFECTION AND RESISTANCE 



The first observations on the general significance of the precip- 

 itin reaction we owe to Tschistovitch 59 and to Bordet. 60 Tschisto- 

 vitch was studying the toxic action of eel serum upon rabbits. This 

 serum, as Kossel 61 had shown, is toxic for rabbits and possesses the 

 property of causing hemolysis of rabbit erythrocytes. Its similarity 

 to ricin, in this respect, stimulated attempts to produce an antitoxic 

 substance against eel serum, even as Ehrlich had produced an an- 

 tiricin. In the course of such experiments Tschistovitch observed 

 that, when eel serum was mixed with the serum of a rabbit which 

 had received several injections of this substance, the mixture became 

 rapidly opalescent and soon a flocculent precipitate was formed. 

 Coincident with this discovery Bordet made a similar observation. 

 He had injected chicken blood into rabbits in the course of experi- 

 ments upon hemagglutination. He found that the serum of the rab- 

 bits so treated acquired the property not only of producing hemolysis 

 and hemagglutination of chicken cells, but also of giving a precipi- 

 tate if mixed with chicken serum. 62 Soon after this precipitins were 

 produced by injecting rabbits with milk (Bordet), egg albumen 

 (Ehrlich, TJhlenhuth), and many other substances, and the speci- 

 ficity of such reactions was demonstrated by Fish, 63 Wassermann and 

 Schiitze, 64 Uhlenhuth, and many others. 



It is apparent from the preceding paragraphs that the discovery 

 of specific antitoxins merely constituted the first step in the formu- 

 lation of a fundamentally important biological law. There is, then, 

 a large group of substances of animal and vegetable origin which 

 call forth the formation of specific reacting bodies when injected 

 into animals.' In order to elicit this response it is necessary that 

 these substances shall penetrate to the physiological interior of the 

 body in a relatively unchanged condition. For this reason any form 

 of injection, subcutaneous, intravenous, or into a serous cavity, is 

 followed, with regularity, by antibody formation, whereas feeding 

 or other means of intraintestinal administration is negative in result, 

 unless abnormal conditions prevail which permit entrance into the 

 blood before the digestive enzymes have decomposed the ingested 

 materials. 



The substances with which antibody-formation may be induced 

 are collectively spoken of as "antigens." 



59 Tschistovitch. Cited by Bordet, loc. cit., and also Ann. Past., 13, 1899. 



60 Bordet. Ann. Past., Vol. 13, 1899. 



61 Kossel. Berl. klin. Woch., No. 7, 1898. 



62 This, we know now, was due to the fact that the blood cells injected 

 were not washed free of chicken serum. Thus chicken serum precipitin was 

 formed as well as were hemagglutinin and hemolysin. 



63 Fish. St. Louis Med. Cour., 1900. Cited from Uhlenhuth. 



6 * Wassermann and Schutze. Deutsche med. Woch., No. 30, 1900, 

 Vereinsbeilage. 



