96 Immunity 



blood-serum from an animal immunized against anthrax 

 enabled the injected animals successfully to resist infection. 

 Behring and Kitasato* found that the blood-serums of 

 animals immunized against diphtheria and tetanus, when 

 mixed with cultures of these respective bacilli, neutralized 

 their power to produce disease. Kitasatof found that if 

 mice were inoculated with tetanus bacilli, they could be 

 saved from the fatal infection by the intra-abdominal 

 injection of some blood-serum from a mouse immunized 

 against tetanus, even after symptoms of the disease had 

 appeared. Ehrlicht showed that the blood-serums of 

 animals immunized against abrin and ricin could save other 

 animals from the fatal effects of these respective alkaloids. 

 Phisalix and Bertrand, and later Calmette, || found the 

 blood-serum of animals immunized against the venoms of 

 serpents, similarly possessed the power of neutralizing the 

 poisonous effects of the venoms. Kossel** found that the 

 blood-serum of animals immunized against the poisonous 

 blood-serum of eels, contained a body which destroyed or 

 neutralized the effects of the eels' serum. 



Thus, it is shown that in each case in which defensive re- 

 actions are stimulated in experiment animals, these reactions 

 are accompanied by the appearance in the blood-serum of 

 those animals of factors that can be utilized to defend other 

 animals in whose bodies no similar reactions have been pro- 

 duced. 



When the defensive action departs from the simple type, 

 and is complicated by the necessary association of immune 

 and complementary bodies, the difficulty of producing passive 

 immunity increases because two factors must be simultane- 

 ously present in the serum used. Thus, to enable an animal 

 to destroy or dissolve an infecting micro-organism by which 

 it is invaded and which its own defensive mechanisms cannot 

 overcome, it is insufficient to inject the serum of an animal 

 immunized against that bacterium, because such serum 

 contains only an increased quantity of the immune or in- 

 termediate body, and no increase in the complement. The 



*" Deutsche med. Wochenschrift," 1890, No. 49. 



t " Zeitschrift fur Hygiene," 1892, xn, p. 256. 



t " Deutsche med. Wochenschrift," 1891, Nos. 32 and 44. 



"Compte rendu Acad. des Sciences de Paris," cxvm, p. 556. 



|| " Ann. de 1'Inst. Pasteur," 1894, vm, p. 275. 



** " Berliner klin. Woch.," 1898, p. 152. 



