CHAPTER XXVII. 

 RECEPTORS OF THE FIRST ORDER. 



ANTITOXINS— ANTIENZYMES. 



The general characteristics of toxins have been described 

 (Chapter XII). It has been stated that they are more or 

 less specific in their action on cells. In order to affect a cell 

 it is evident that a toxin must enter into chemical combina- 

 tion with it. This implies that the toxin molecule possesses 

 a chemical group which can combine with the cell. This 

 group is called the haptophore or combining group. The 

 toxic or injurious portion of the toxin molecule is likewise 

 spoken of as the toxophore group. When a toxin is intro- ■ 

 duced into the body its haptophore group combines with 

 suitable receptors in different cells of the body. If not too 

 much of the toxin is given, instead of injuring, it acts as a 

 chemical stimulus to the cell in the manner already described. 

 The cell in response produces more of the specific thing, 

 which in this instance is more receptors which can combine 

 with the toxin, i. e., with its haptophore group. If the stim- 

 ulus is kept up, more and more of these receptors are pro- 

 duced until an excess for the cell accumulates, which excess 

 is excreted from the individual cell and becomes free in the 

 blood. These free receptors have, of course, the capacity 

 to combine with toxin through its haptophore group. When 

 the toxin is combined with these free receptors, it cannot 

 combine with any other receptors, e. g., those in another 

 cell and hence cannot injure another cell. These free recep- 

 tors constitute, in this case, aniiioxin, so-called because they 

 can combine with toxin and hence neutralize it. Antitoxins 

 are specific — that is, an antitoxin which will combine with 

 the toxin of Bacilliis tetani will not combine with that of 

 Bacterium diphtheriw, or of Bacilhts botulinus, or of any 

 other toxin, vegetable or animal. 



