120 Immunity 



Closely connected with these various reactions are certain 

 others variously spoken of as cytotoxic, cytolytic, hemolytic, 

 bacteriolytic, etc. The first observation bearing upon these 

 was made by R. Pfeiffer,* who found that when guinea-pigs 

 received frequent intraperitoneal injections of cholera spirilla 

 and became thoroughly immunized, their serum behaved 

 very peculiarly toward the bacteria in the peritoneal cavity 

 of freshly infected animals, in that it caused them to become 

 aggregated into granular masses and subsequently to dis- 

 appear. This became known as " Pfeiffer 's phenomenon." 

 The serum of the immunized animal was devoid of action 

 by itself, the serum of the infected animal was inactive, but 

 the combination of the two brought about dissolution of 

 the micro-organisms. Later it was shown by Metschnikofff 

 that the living animal was not a factor in the process, but 

 that what was seen in the peritoneal cavity could be re- 

 produced in a test-tube, though not quite as well. 



BordetJ made frequent injections of defibrinated rabbits' 

 blood into guinea-pigs, and obtained a serum that had a 

 solvent action upon the rabbit's corpuscles in -vitro, and 

 showed that the induced hemolysis resembled in all points 

 the bacteriolysis. 



Ehrlich and Morgenroth studied the hemolytic action 

 of the serum of goats that had been frequently injected with 

 the defibrinated blood of sheep and goats, and were able to 

 point out the mechanism of the corpuscle solution or hemo- 

 lysis. It was found to depend upon two associated factors, 

 one of which, the lysin or solvent, was present in normal 

 blood, and was called "addiment" or "complement," and 

 another present only in the serum of the reactive animals, 

 called the "immune body" or "intermediate body." 

 The former was labile and easily destroyed by heat, the 

 latter stabile and not affected by heat up to the point of 

 coagulation. The experiments were confirmed by von 

 Diingern and many others. It is to be observed in passing 

 that this reaction differs from the direct solution of the cor- 

 puscles in vitro by cobralysin, which was studied by Myers, 1 1 

 and tetanolysin, studied by Madsen,** in that it is inter- 

 mediate, and only brought about by the cooperation of two 



* "Deutsche med. Wochenschrift," 1896, No. 7. 

 f "Ann. de 1'Inst. Pasteur," 1895. % Ibid., XH, 1898. 



"Berliner klin. Wochenschrift," 1899. 

 || "Trans. Path. Soc. of London," u. 

 ** " Zeitschr. f. Hyg.," 1899, xxxm, p. 239. 



