6 IMMUNE SERA 



observations by Buchner 1 and by Roux and Martin 

 threw doubt, however, on the correctness of Beh- 

 rings view that the toxin was neutralized by the 

 specific serum just as a base was neutralized by an 

 acid. It was claimed, for example, that the specific 

 serum acted mainly on the body cells causing them 

 to become non-susceptible to the poison in question. 

 Various theories were formulated to account for the 

 production of the antitoxins, their specificity, etc., 

 but of them all only one has at all maintained itself. 

 This, is the so-called side-chain theory, which was 

 formulated by Ehrlich 2 in 1897. 



Ehrlich's Side-Chain Theory. Originally the 

 side-chain theory was applied by Ehrlich only to 

 the production of the specific antitoxins, i.e., sub- 

 stances 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 bacteri- 

 cidal and haemolytic substances in the serum of 

 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 



1 Buchner, Miinchener med. Wochenschrift, 1894. 

 1 Ehrlich, Klinisches Jahrbuch, 1897. 



