10 VACCINE AND SERUM THERAPY 



normal blood 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 power was called by Buchner 

 ''alexin"; later Ehrlich renamed this substance, 

 "complement," by which name it is now most 

 commonly known. In 1890 von Behring, and soon 

 after Ehrlich, made the important discovery that 

 specific antitoxins could be produced in the sera of 

 living animals against the poisons of some of the 

 higher plants, and Calmette about this time succeeded 

 in producing antitoxins against the poison of 

 snakes, as well as against scorpion poison. Wasser- 

 mann produced an antitoxin against the poison of the 

 Bacillus jyyocijaneus. Thus a large number of poisons 

 of animal, plant, and bacterial origin have been found 

 capable of producing specific antibodies in the sera of 

 animals into which they are injected. The formation 

 of antitoxins directed against soluble poisons did 

 not, however, explain the immunity acquired by 

 animals against bacteria like B. anthracis and others 

 which, unlike tetanus, etc., produced little or no 

 soluble poison. Much light was shed upon this 

 phase by the discovery of Pfeiffer, who showed that 

 when cholera spirilla were injected into the peritoneal 

 cavity of cholera-immune guinea-pigs, the micro- 

 organisms rapidly swelled up, became granular, and 

 often underwent complete solution. This same 



