20 IMMUNE SERA. 



Originally the side-chain theory was applied by 

 Ehrlich only to the production of the specific anti- 

 toxins, i.e., substances in the blood which act not 

 only on the living bacteria but also and especially 

 on their dissolved toxins. Later on he extended 

 it so as to apply also to the formation of specific 

 bactericidal and hsemolytic substances in the serum 

 of animals treated with living bacteria or with 

 animal cells. 



Toxins, their Toxophore and Haptophore Groups 

 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 temperatures than 

 at higher, stronger in concentrated than in di- 

 lute form. Ehrlich could further show that each 

 poison for which by the process of immunizing 

 one can develop a counter-poison possesses two 

 groups which are concerned in the combination 

 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, there- 

 fore, might lose the one, the toxophore, and still be 

 capable by means of its haptophore group of com- 

 bining with antitoxin. Such a modified poison, 

 which because of the loss of the toxophore group 



