428 INFECTION AND RESISTANCE 



these reactions, according to von Pirquet and Schick, the nature of 

 the reaction being, within certain limits, determined by the interval 

 ensuing between the first and the second injection. Thus, when the 

 interval was twenty-one days or less the immediate reaction alone 

 was noticed. When the interval was between two and six months 

 both the immediate and accelerated reactions were present, and when 

 the interval was still longer (seven months or more) the accelerated 

 reaction alone was present. Isolated exceptions to this are noted in 

 the series of sixty-one cases so reported. 



Currie, 6 7 who has made similar studies, confirms the results of 

 von Pirquet and Schick in all essentials, and agrees with their state- 

 ment that the nature of the reaction is chiefly dependent upon the 

 interval between injections. 



That the entire train of symptoms, as well as the mere fact of 

 their dependence upon an injection of a foreign protein, rather than 

 upon the antitoxin itself, force upon us the analogy with anaphy- 

 laxis is clear. Moreover, this analogy becomes almost an identity 

 when we can show, as von Pirquet and Schick have done, that the 

 first injection has apparently sensitized the subject, in that the 

 second administrations are fraught with more violent and serious 

 reactions, dependent to a great extent, as in experimental anaphy- 

 laxis, upon the time intervening. If serum-sickness is truly an 

 anaphylactic phenomenon, however, it is still by no means clear why 

 symptoms should at all ensue after the first injection. Many ex- 

 planations have been offered for this; none of them, however, from 

 the very nature of the problem itself, can be finally accepted as 

 proved. Two possible explanations appear from the experimental 

 work of Rosenau and Anderson quoted above. These workers, we 

 have seen, showed among other things that the state of hypersus- 

 ceptibility could be transmitted from mother to offspring, and that 

 sensitization by way of the intestinal canal was at least possible. 

 Both of these factors may have determinative significance in the 

 present case. 8 There may be, because of such conditions, a pre- 

 existent sensitization which, especially in cases of accidental injec- 

 tion of the antitoxin directly into a small vein (an accident prob- 

 ably not infrequent in deep muscular injections), may possibly ex- 

 plain the few instances of sudden death following the first antitoxin 

 injection and the isolated instances of "immediate" reaction follow- 

 ing "first" injections. Rosenau has also suggested recently that sensi- 

 tization may be unconsciously acquired against various forms of 

 protein by absorption through the lungs of the organic matter car- 

 ried in the expired breath of animals. In this way possibly hyper- 



6 Currie. Jour, of Hyg., Vol. 7, 1907. 



7 See also Goodall, Jour, of Hyg., 7, 1907. 



8 Regarding intestinal sensitization see also Richet, C. R. de la Soc. de 

 Biol., Vol. 70, 1911; Lesne et Dreyfus, C. E. de la Soc. de Biol., Vol. 70, 1911. 



