SPECIFIC BACTERIAL PRODUCTS 459 



ically bound to the cell. Later Ehrlich called the side chains 

 ' ' receptors. ' ' 



All forms of toxins are supposed to consist of two groups 

 of atoms, which combine in an equally energetic manner with 

 antitoxin or with suitable receptors in the cells, but differ in 

 their resistance to heat and other destructive agents. The less 

 resistant form passes readily into a modified toxin or toxoid 

 substance which has the same affinity for the antitoxin or the 

 cell receptors as the original toxin but is not so poisonous. 

 Ehrlich believed that the facts were best explained on the sup- 

 position that the toxic molecule contains two independent 

 groups of atoms one of which he designated the haptophorous 

 (combining) and the other as the toxophorous (poisonous) 

 group. It is by the action of the haptophorous group that 

 toxin unites with antitoxin or the cell receptors.* The toxo- 

 phorous group is unstable, but after its destruction the mole- 

 cule still unites with the antitoxin or the sensitive molecule 

 through its retained haptophorous group. 



chemical conception from which the term side chain was borrowed. 

 The formula given is that of salicylic acid in which the 

 OH 



C 

 H C^ ^C COOH 



H-C\ ^C H 

 C 



benzol ring represents the "Leistungs-Kern," or radicle, while COOH 

 and OH are side chains by means of which other substances may be 

 brought into relation with the "radicle." 



* Bordet believed, contrary to Ehrlich, that toxin unites in dif- 

 ferent multiples with antitoxin, so that the toxin molecule may 

 have its affinity slightly, partly or wholly satisfied by antitoxin. 

 Slightly satisfied, it is still feebly toxic; combined with a larger 

 amount of antitoxin, it is not toxic; but still may, when absorbed 

 into the system, lead to the production of antitoxin. Fully saturated, 

 it has no poisonous properties, and no ability to stimulate the pro- 

 duction of antitoxin. 



