ANAPHYLAXIS 173 



for them to accumulate in sufficient number 

 and virulence to produce symptoms. But serum 

 is not a poison capable of multiplication. 

 Pfeiffer's work on the endotoxins led to the view 

 that the antibodies played an important part in 

 bringing on the symptoms by setting free the endo- 

 toxins. The results of these observations are very 

 closely related to von Pirquet and Schick's explan- 

 ation of the production of serum disease. The 

 endotoxin theory, in the sense of bacteriolysis, 

 naturally cannot be applied to albuminous sub- 

 stances in solution. We can only accept it in the 

 sense that by means of the reaction between the 

 antibodies and the antigen the poisonous substance 

 is formed. The period of incubation, both in serum 

 rashes and in bacterial infections, is thus readily 

 understood, for it is at once apparent that the 

 formation of antibodies requires time. The 

 general idea underlying von Pirquet and Schick's 

 theory of serum disease is that the injection of the 

 horse serum into man causes the development of 

 specific reaction products which are able to act upon 

 the antigens introduced. These antibodies encoun- 

 ter the antigens, i.e., some of the serum still present 

 in the body, and so give rise to a poisonous sub- 

 stance. This accounts also for the cases of "imme- 

 diate reaction" described by von Pirquet and Schick 

 in which the second injection of a serum produces 

 an attack of serum disease without any period of 



