ANTIGEN AND CELL RECEPTORS. 349 



this experiment demonstrates positively that 

 chemical union of tetanus toxin takes place with 

 constituents of the nervous tissue. The toxin hav- 

 ing been completely neutralized can not again be 

 extracted from the tissue. The condition is the 

 opposite in relation to some poisonous alkaloids, 

 as strychnin, which it appears does not combine 

 with the protoplasm firmly and may again be ex- 

 tracted by simple methods. 



Von Dungern conducted very important work 

 with the precipitins, which is interpreted as show- 

 ing that albuminous substances other than toxins 

 are taken up chemically by the cells. He injected 

 considerable quantities of a foreign serum into the 

 veins of rabbits and studied its disappearance from 

 the blood of the injected animal. Traces of the 

 foreign serum could be recognized by treating the 

 rabbit serum with a specific precipitin for the for- 

 mer, the precipitin having been obtained pre- 

 viously by the immunization of other animals. 

 The foreign serum disappeared from the circula- 

 tion of the rabbit with some rapidity and since it 

 could not be demonstrated in the excretions, it 

 seemed necessary to assume that it had been bound 

 by the cells, that is to say, by the cell receptors. 



Third tenet: Is there any direct experimental Proliferation 



* of Receptors. 



proof that those constituents of cells which have 

 been designated as cell receptors actually undergo 

 multiplication in the cell itself as a preliminary to 

 their discharge into the circulation in the form of 

 antibodies? If this condition could be demon- 

 strated in one instance, one might reasonably con- 

 sider that it typifies a law according to which all 

 antibodies are formed. Further experiments by 



