ANTI-ANAPHYLAXIS 561 



two days later by an intravenous injection (0.1 to 0.5 c.c.) of the antigen. 

 The immune serum may be prepared by injecting rabbits with horse 

 serum, after the methods for the production of precipitins described in 

 Chapter IV. 



The duration of passive sensitization is quite variable. Weil x found 

 that guinea-pigs sensitized with a homologous serum, that is, with the 

 serum of another guinea-pig sensitized with horse serum, remain typic- 

 ally anaphylactic as long as seventy days after the injection. With 

 heterologous sensitization, however, as with the serum of a sensitized 

 rabbit, hypersensitiveness is almost invariabry lost by the tenth day. 

 One explanation of this would be that a heterologous serum is excreted 

 more rapidly than a homologous serum, a 'condition commonly observed 

 in serum therapy with any heterologous serum. 



The Mechanism of Passive Anaphylaxis. Presumably the mecha- 

 nism of passive anaphylaxis is relatively simple, and consists in the 

 transfer of the specific protein sensitizer or amboceptor that unites the 

 anaphylactogen or protein antigen with a complement, bringing about 

 lysis or cleavage of the protein and liberation of the toxic moiety re- 

 sponsible for the lesions and symptoms of anaphylaxis. In other words, 

 the mechanism of passive anaphylaxis may be likened to passive anti- 

 bacterial immunization, with, however, one important clinical difference, 

 namely, that whereas in the former the microorganisms are destroyed 

 without apparent injury to the host, in anaphylaxis the body-cells are 

 acutely poisoned. However, a similar phenomenon in the serum 

 treatment of disease, with lysis of bacteria, may be overshadowed or 

 possibly prevented by a condition of anti-anaphylaxis. 



ANTI-ANAPHYLAXIS 



The term anti-anaphylaxis was first applied by Besredka and Stein- 

 hardt to a condition of insensibility to further injection of the anaphylac- 

 togen that may follow recovery from anaphylaxis, or be induced arti- 

 ficially by a single or by repeated small injections of the anaphylactogen 

 during the incubation period following the first injection, and before 

 sensitization is completed. The state is usually only temporary, the 

 animal gradually becomes sensitive again after three weeks. 



Theobald Smith had observed that those guinea-pigs that had re- 

 ceived the largest dose of diphtheria toxin-antitoxin mixture more 

 frequently survived the second dose than did those that received smaller 



1 Jour. Med. Research, 1913, 28, No. 2, 359. 

 36 



