1 6 IMMUNE SERA 



animals treated with living bacteria or with animal 

 cells. 



Toxins Toxoids Special Function of the Side 

 Chains. The basis of the theory is the fact that 

 poison and counter-poison, toxin and antitoxin, 

 combine directly in any given quantity. This 

 combination always occurs in definite proportions 

 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 



