CHAPTER XV 



ANAPHYLAXIS 



FUNDAMENTAL FACTS 



THE fundamental principle of active immunization is the fact 

 that the treatment of animals with bacteria or bacterial products, 

 carried out according to certain empirically determined methods, 

 leads to increased tolerance or resistance. The limitations within 

 which this statement is true, and the variable factors to which it is 

 subject, we have considered in the foregoing discussions dealing with 

 the antibody-antigen reactions. 



Although these reactions were studied at first purely from the 

 point of view of increased resistance to infection, the most extensive 

 studies of antibody formation have been made with such antigens as 

 blood cells, serum, and other substances which are in themselves en- 

 tirely harmless. For, in such reactions, great simplicity and ease of 

 experimentation could be attained. For a time, therefore, the pri- 

 mary problem of increased tolerance or resistance was relegated to a 

 secondary position, or, at least, dealt with chiefly by analogy, and the 

 phenomena of increased antibody formation and increased resistance 

 to the antigen were assumed to maintain a more or less strict paral- 

 lelism. 



That the problem is not as simple as this has gradually become 

 obvious. We have come to recognize that the treatment of animals 

 with any antigen, bacterial or otherwise, though leading to increased 

 tolerance under certain conditions and within definite limits, may, 

 under other conditions, give rise to the very opposite, that is, to an 

 intolerance or increased susceptibility. 



The development of this knowledge, like much else that serum 

 study has revealed in the last fifteen years, takes root in isolated 

 observations scattered throughout the early literature, but often 

 regarded as merely noteworthy accidents or technical errors. This 

 particular problem, moreover, was confused by the fact that some of 

 the earliest observations regarding hypersusceptibility were made in 

 the course of experimentation with diphtheria and tetanus toxins, 

 antigenic substances toxic in themselves and, therefore, as we shall 

 see, clouding some of the basic principles apparently involved in the 

 phenomenon of which we now speak as anaphylaxis. We will for the 

 present, therefore, limit our discussion to the development of the 



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