Experimental Investigation of the Problems of Immunity 101 



Wassermann and Schiitze* found that when cow's milk was ; 

 repeatedly injected into rabbits, their serum acquired the property 

 of occasioning a precipitate when added to cows' milk, but not when 

 added to goats' or any other milk. If, however, the rabbit had been 

 repeatedly injected with goats' milk or human milk, its serum would 

 precipitate with those milks respectively, and not with cow's milk. 

 The reaction was thus shown to be specific. 



Myers f found that the repeated intraperitoneal injection of 

 egg-albumen into rabbits caused their serum to give a dense pre- 

 cipitate when added to solutions of egg-albumen. 



Tchisto witch t found that eels' serum injected into animals 

 produced a reaction in which immunity to its poisonous action was 

 associated with the ability of their serum to produce a precipitate 

 when added to the eels' serum. 



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 disappear. 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 MetschnikofT|| that the living animal was not a factor 

 in the process, but that what was seen in the peritoneal cavity could 

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



Bordet** 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. 



Ehrlichf f and Morgenroth studied the hemolytic action of the 

 serum of goats that had been frequently injected with the de- 

 fibrinated blood of sheep and goats, and were able to point out the 

 mechanism of the corpuscle solution or hemolysis. 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 



* "Deutsche med. Woch.," 1900. 



f "Lancet," 1900, n. 



j "Ann. de 1'Inst. Pasteur," vol. XIIT, 406. 



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



|| "Ann. de 1'Inst. Pasteur," 1895. 

 ** Ibid., 1898, XTI. 

 ft "Berliner klin. Wochenschrift," 1899. 



