BACTERICIDAL PROPERTIES OF BLOOD SERUM 141 



serum had lost its power completely, but this was restored to it by 

 the addition of the fresh normal serum. He noted, furthermore, 

 that the specific nature of the bacteriolysis by the immune serum was 

 unchanged after it had been inactivated by heat and reactivated sub- 

 sequently by the normal serum. The inference was plain. Immu- 

 nization of an animal incites the production, in the blood of this 

 animal, of a ''preventive" substance, which is moderately resistant 

 to heat, and which is specific for the bacteria employed in the im- 

 munization. This substance cannot act upon the bacteria alone, how- 

 ever, but depends for its effective functionation upon the coopera- 

 tion of another substance present universally in normal serum, the 

 "bactericidal" substance, which is non-specific, corresponds to Buch- 

 ner's alexin, and is apparently not increased by the process of im- 

 munization. These are the fundamental facts revealed by the early 

 studies of Bordet, and they are stated in the present connection 

 merely as experimental facts, without further elaboration of the 

 later theoretical interpretation placed upon them by Bordet himself 

 and by Ehrlich and his followers. . 



In the course of these studies Bordet 17 had used the immune 

 serum produced in a goat by injection of cholera spirilla. As normal 

 serum he had used guinea-pig serum, and the latter frequently con- 

 tained a few blood corpuscles. He noticed that these corpuscle? were 

 frequently clumped in the goat serum and correlated this with the 

 similar clumping (agglutination) of cholera organisms which he 

 had noticed in this and other sera. In his incidental observation of 

 the phenomenon of agglutination he had concluded that the living 

 nature of the bacteria had no importance as far as their agglutina- 

 tion was concerned, dead organisms being as readily agglutinated as 

 living. 



Reasoning from this similarity between blood cells and bacteria 

 in their behavior in serum, it occurred to him that the phenomena 

 both of agglutination and of lysis might be expressions of general 

 biological laws, not limited to bacteria. Accordingly he injected 

 rabbit blood into guinea pigs, and examined the serum of animals 

 so treated for its action upon rabbit corpuscles, in vitro. He found 

 that the sera of "blood-immune" animals had acquired not only in- 

 creased agglutinative power against the corpuscles injected, but had 

 also acquired specific "hemolytic" powers, that is, the property of 

 causing a solution of hemoglobin out of the red cells. (For the 

 process of serum hemolysis does not consist of a complete dissolution 

 of the red corpuscles, but rather in the liberation of the hemoglobin 

 from the cell stromata.) The latter (shadow forms) can be recovered 

 undisintegrated by the centrifugation of hemolyzed blood. The 



17 See Bordet's own account in a "Resume of Immunity"; "Studies in 

 Immunity," Bordet, collected and translated by Gay, Wiley & Son, N. Y., 

 1909. 



