ANTITOXINS 7 



following the laws of chemical combination; and, 

 still following those laws, is slower at lower tem- 

 peratures than at higher, stronger in concentrated 

 than in dilute form. Ehrlich could further show 

 that each poison for which by the process of immun- 

 izing one can develop a counter-poison possesses 

 two groups which are concerned in the combina- 

 tion with the counter-poison or antitoxin. One of 

 these, the so-called haptophore group, is the combin- 

 ing group proper; the other, the toxophore group, 

 is the carrier of the poison. A poison molecule, 

 therefore, might lose the one, the toxophore, and 

 still be capable by means of its haptophore group 

 of combining with antitoxin. Such a modified 

 poison, which because of the loss of the toxophore 

 group can hardly be called a poison, but which still 

 possesses the power to combine with antitoxin, 

 Ehrlich calls a toxoid. Toxoids may be produced 

 spontaneously in old poisons through decomposi- 

 tion of the poison molecule, or they may be pro- 

 duced artificially by causing certain destructive 

 agents such as heat or chemicals to act on bacterial 

 poisons. The toxophore group is a very delicate 

 one and much more readily decomposed than the 

 combining (haptophore) group. Ehrlich reasoned 

 that in order for a poison to be toxic to an organ- 

 ism, i.e., in order that the toxophore group be able 

 to act destructively on a cell, it is necessary for the 

 haptophore group of the poison to combine with 



