252 RESISTANCE AND IMMUNITY 



sickness. Arthus/ moreover, had proved that a second injection of 

 horse serum into rabbits frequently causes a very intense reaction, so 

 much so that this formerly perfectly harmless procedure becomes dis- 

 tinctly injurious. Quite similarly, it had been observed that a tuber- 

 culous person is hypersensitive to tuberculin and that injections of 

 cocain eventually give rise to an increased susceptibility, as evinced 

 by undue rises in the body temperature.^ A similar hypersensitiveness 

 follows the repeated administration of apomorphin.^ Anaphylaxis, 

 therefore, may be active and passive, because it is possible to render 

 an animal anaphylactic by these injections and also to transfer this 

 state from a sensitized to a normal animal. The latter process 

 requires the injection of the serum of an anaphylactic animal which is 

 then followed, say 24 hours later, by an injection of the antigen origi- 

 nally used to produce this condition in the first animal. 



Numerous theories have been advanced to explain anaphylaxis. 

 In general it may be said to be a reaction between the antigen and the 

 specific antibody. In the same way as antibodies are developed after 

 a definite period of incubation, a certain antigen may eventually give 

 rise to anaphylactic bodies, such as toxogenin (Richet) anaphylactin 

 or sensibiHn. This complex formed by the antigen and antibody be- 

 comes poisonous in the course of this reaction, but it may also be true 

 that the reaction affects the medium (blood-serum) in such a way 

 that it assumes toxic properties. 



iSoc. biolog., Iv, 1903, 817. 



2 Adnico, Arch. ital. de bioL, xx, 1894. 



3 Richet, Soc. biolog., Iviii, 1905, 955. 



