198 INFECTION AND IMMUNITY 



ease with which it could be obtained and studied, claimed the first 

 and closest attention. The bactericidal properties of normal blood 

 serum noted in 1886 by Nuttall/ v. Fodor,^ and Fliigge, moreover, aided 

 in pointing to this tissue as primarily the seat of the immunizing 

 agents. It is an interesting historical fact, that, long before this time, 

 the English physician Hunter had noted that blood did not decompose 

 so rapidly as other animal tissues. 



The study of the blood serimi of immunized animals as to simple 

 changes in chemical composition or physical properties has shed little 

 light upon the subject. Beljaeff ^ in a recent investigation found little 

 or no alteration from the normal in the blood sera of immunized animals 

 as to index of refraction, specific gravity, and alkalinity. Joachim * and 

 Moll agree in stating that immune blood serum is comparatively richer 

 in globuUn than normal serum. Similar observations had been made 

 by Hiss and Atkinson * and others. Important and significant as these 

 purely chemical observations are, they have helped little in explaining 

 the nature of the processes going on in immune sera. The first actual 

 light was thrown upon the mysterious phenomena of immunity by 

 the investigations of Nuttall," v. Fodor, Buchner, and others, who not 

 only demonstrated the power of normal blood serum to destroy bacteria, 

 but also showed that this property of blood serum became diminished 

 with age and was destroyed completely by heating to 56° C. The 

 thermolabile substance of the blood serum possessing this pow^er was 

 called by Buchner,' alexin. 



Soon after this work, Behring, in collaboration with Kitasato ' and 

 Wernicke," in 1890 and 1892, made further important advances in the 

 elucidation of the immunizing processes by showing that the blood sera 

 of animals actively immunized against the toxins of diphtheria and tet- 

 anus would protect normal animals against the poisons of these diseases. 

 He believed, at the time of discovery, that such sera contained substances 

 which had the power of destroying the specific toxins which had been 



^ NuttaU, Zeit. f. Hyg., i, 1886. 



^ V. Fodor, Deut. med. Woch., 1886. 



3 Beljaeff, Cent. f. Bakt., xxxiii. 



* Joachim, Pflugers Archiv, xoiii. 



^Hiss and Atkinson, Jour. Exper. Med., v, 1900. 



'NuttaU, Zeit. f. Hyg., 1886. 



T Buchner, Cent. f. Bakt., i, 1889. 



8 Behring und Kitasato, Deut. med. Woch., 1890, No. 49. 



• Behring und Wernicke, Zeit. f. Hyg., 1892. 



