CHAPTER XI 



IMMUNITY 



Toxins and antitoxins — Chemical and physical conceptions of immunity. 



Side-chain theory — Origin of the antibodies — Theory of chemical equi- 

 librium. 



The physical point of view : Bordet — Phenomena of absorption or molecular 

 adhesion — Explanation of specificity — Analogies between the reactions 

 of antibodies and the reactions of colloids — Lipoid actions. 



Phagocytosis and toxins — The body plays an essential part — Origin of 

 antibodies and Wassermann's experiments — The phagocytes in their 

 connection with mineral poisons and microbial poisons, toxins, and 

 endotoxins. 



It was the discovery of antitoxins which inaugurated the study 

 of antibodies. It was the necessity of explaining the action of 

 antitoxins on toxins which gave rise to the theories on this 

 peculiar problem and on antibodies and immunity in general. 



It was thought at first that in the immunized animal which 

 manufactures the antitoxin, as well as in the animal immunized 

 by the injection of the antitoxic serum, the cells play a part. 

 Buchner enunciated the hypothesis that the body produces 

 antitoxin by transforming the toxin ; he quoted, as a distant 

 analogy, the transformation of one compound into another by 

 polymerization. But it is difificult to understand how there 

 could be such a disproportion between the toxin injected and 

 the antitoxin produced; the horse produces, according to 

 Knorr, for one unit of toxin injected 100,000 units of anti- 

 toxin. 



Buchner performed a pretty experiment, which has lost none 

 of its interest, by showing that after accounting for the 

 differences in weight and in natural susceptibility, a mixture of 



