ANAPHYLAXIS 381 



moreover, it appeared that not only by the blood of sensitive animals 

 can anaphylaxis be transferred, but that this can also be done by 

 injecting the blood of animals that have once been sensitive but have 

 subsequently been rendered antianaphylactic or refractory. Analo- 

 gous to this observation is the fact, observed by these authors as well 

 as by Friedemann, that the young of antianaphylactic mothers are 

 not refractory but hypersusceptible. This observation, unquestion- 

 ably correct, since it has been confirmed by several other workers, is 

 astonishing and contrary to expectation. It has had no inconsider- 

 able bearing upon our theoretical understanding of anaphylaxis. 



It was soon found out, too, that hypersusceptibility was con- 

 veyed not only by the sera of sensitive and of refractory animals, 

 but that it could likewise be transferred by the precipitating sera 

 of animals systematically immunized with a foreign protein. 



This method was later employed by Doerr and Russ 78 in their 

 quantitative studies on the relations between anaphylactic antigen 

 and antibody. We are confronted, then, with the curious facts that 

 animals may be passively sensitized: 



(a) by the serum of a sensitized animal. 



(b) by the serum of an animal not yet sensitive in the pre- 

 anaphy lactic period (8th day, Otto). 



(c) by the serum of an antianaphylactic animal. 



(d) by the precipitating serum of an "immunized" 79 animal. 



Lewis further showed that normal guinea pigs could be ren- 

 dered hypersusceptible with the blood of congenitally sensitive 

 animals. 



Passive sensitization is carried by the blood serum purely, since, 

 in ordinary cases, as Rosenau and Anderson have shown, the blood 

 corpuscles and tissues of a sensitive animal do not convey the hyper- 

 susceptibility. An exception to this will be noted later when we 

 come to discuss Bail's experiments on the passive transfer of tuber- 

 culin sensitiveness. 



Passive sensitization, once established, may persist for as long 

 as 3 or 4 weeks, though Rosenau and Anderson found that animals 

 tested 26 days after treatment reacted but weakly. In the young 

 of anaphylactic mothers Otto has observed positive reactions as long 

 as 44 days after birth, though fatal results were obtained in pigs only 

 a few days old. 



Throughout the earlier investigations upon passive sensitization 

 the curious fact recurs in the experiments of successive workers that 



78 Doerr and Russ. Zeitschr. f. Immunitatsforschung, Vol. 3, 1909. 



79 We must never forget that the term "immunized" as applied to animals 

 treated with harmless protein is an analogy and not absolutely correct. 

 Such animals, though probably capable of assimilating larger quantities of 

 foreign injected protein than normal ones, and this more rapidly, may never- 

 theless be not a whit more tolerant of the antigen sometimes even extremely 

 sensitive and vulnerable. 



