268 PROTEIN POISONS 



that living cultures of the cholera, typhoid, colon, and 

 many other bacilli secrete no toxin, but that the cellular 

 proteins of these organisms are themselves poisonous. 

 By these experiments Pfeiffer laid the foundation of our 

 knowledge of lytic immunity, which, as we shall see, is 

 the chief protective function in the anaphylactic state. 

 The anaphylactogen which he used was the cellular protein 

 of the cholera bacillus. This caused the elaboration of 

 the toxogen, which is contained in his lytic serum, and this 

 digesting the anaphylactogen on the second injection, split 

 it up with the liberation of the poison. From these researches 

 Pfeiffer developed his theory of endotoxins, which we will 

 discuss later. 



The next important work done along this line was that 

 of Weichardt. 1 He extracted the proteins from placental 

 cells, and found that the blood serum of rabbits which had 

 received repeated injections of such extracts when mixed 

 with the anaphylactogen either in vitro or in vivo, produced 

 a poison which killed rabbits with the typical symptoms of 

 anaphylactic shock. 



The toxogen exists in the blood serum and in the tissues 

 of sensitized animals, and with the former it may be trans- 

 ferred to normal animals, thus establishing passive anaphyl- 

 axis. As we have seen, passive anaphylaxis may be induced 

 in either homologous or heterologous animals. In the study 

 of anaphylactic sera one observation has, in our opinion, 

 led several authorities astray. It has been found that 

 passive anaphylaxis, in some instances at least, may be 

 induced with anaphylactic serum, either unheated or heated 

 (56). From this it has been inferred that the toxogen is 

 thermostabile. In fact, the toxogen consists of amboceptor 

 and complement, and the latter is destroyed by a tempera- 

 ture of 56; but when heated, anaphylactic serum is injected 

 into a fresh animal the recipient does or may furnish the 

 complement. Whether it does or does not, determines the 

 degree of success in inducing passive anaphylaxis, which, 

 as we have seen, is not constantly accomplished. 



1 Berl. therup. Woch., 1903, No. 1. 



