394 INFECTION AND IMMUNITY. 



is due to an exhaustion of anaphylactic antibody. 

 In animals which have been actively sensitized, 

 the period is a transient one, followed by a return 

 of hypersusceptibility due to continued production 

 of antibodies. In passively sensitized animals, as 

 there is no further source of antibodies, the result 

 depends on the amount of antigen injected. If, 

 for instance, the animal is insufficiently sensitive 

 to allow of death from a large toxic dose, the anti- 

 gen remaining will produce an active sensitization. 

 If the antigen is just enough to neutralize the 

 anaphylactin, the animal will then be, as before, 

 sensitized. If the second dose is too small to 

 neutralize the anaphylactin, that which remains 

 will be capable of producing further reactions. In 

 animals immunized to proteins and which have a 

 high concentration of antibodies in the blood, so 

 that passive anaphylaxis may be transmitted to a 

 second animal by the use of a small quantity of 

 serum of the immune animal, a state of antiana- 

 phylaxis may be produced by injections of amounts 

 of antigen too small to produce a fatal result. 

 In this case, we have an animal which is antiana- 

 phylactic although possessing a serum containing 

 a high concentration of anaphylactin. Friedberger 

 supposes that in this case the receptors of the cells 

 are occupied by anaphylactic antibody which is 

 not reached by the injected antigen, this being 

 neutralized by the circulating anaphylactin. 

 Tuberculin The relation of the tuberculin reaction to ana- 

 phylaxis (see Tuberculosis) has been the subject 

 of much discussion. 



Yamanouchi succeeded in producing anaphyl- 

 actic symptoms in guinea-pigs by sensitizing them 



