344 INFECTION AND IMMUNITY. 



scribed as a cell defect, the defect consisting of the 

 functional elimination of the receptor. The "Leis- 

 tungskwn" as the vital or regulating center of the 

 cell repairs the defect by the formation of new re- 

 ceptors, and in harmony with the hypothesis of 

 Weigert produces not only enough to repair the 

 defect, but a great excess, with the result that 

 many are thrown into the circulation. The anal- 

 ogy of the "Lristtmgslcem" with the benzol ring 

 ean not be carried to this extent, for the latter has 

 no power of reproducing side-chains to take the 

 place of one which has been bound by some new 

 group of atoms. 



It will be appropriate in this place to consider 



of 



's the character of the proof which has been offered 

 Bry ' in support of the three tenets which constitute the 

 framework of the theory of Ehrlich. These three 

 tenets may be expressed as follows: 1. Antitox- 

 ins counteract toxins by entering into chemical 

 union with them; a similar union takes place be- 

 tween other antibodies ^nd their homologous sub- 

 stances. 2. Toxins in injuring cells combine 

 chemically with a definite constituent of the proto- 

 plasm, the cell receptor; other antigenous sub- 

 stances 2 enter into similar union with the appro- 

 priate receptors of cells. 3. The specific antibodies 

 of the serum are new-formed receptors identical in 

 structure with those which, as cell constituents, 

 had combined with the homologous antigens. 

 chemical First tenet : In the early days of studies on im- 

 munity (1890-1897), the action of a toxin and the 



1 gens" efficacy of an antitoxin could be determined only 



2. An antigen or an antigenous substance is one which 

 is able to cause the formation of an antibody. 



