Summary 561 



of the highest importance from the point of view of immunity in 

 general, that the resistance offered to micro-organisms in no way 

 imphes insusceptibility to their poisons. The view has frequently 

 been expressed that, in acquired immunity at least, the animal must 

 first acquire immunity against the microbial toxins, after which the 

 micro-organisms, deprived of their principal weapon, descend to 

 the rank of inoffensive saprophytes. Such cases may be found, 

 but it is none the less true that immunity against micro-organisms 

 may be acquired independently of that against the toxins, and that 

 this constitutes the general rule. 



Immunity is much more readily acquired against micro-organisms 

 than against their toxins. Hence, antimicrobial vaccination was 

 accomplished by science before that against their toxins. In the 

 early researches on this subject antitoxic immunity appeared to 

 be very diificult of attainment, and it was only after the discovery 

 made by von Behring, who inaugurated a new path in microbiology, 

 that better results were obtained. Von Behring not only suc- 

 ceeded in immunising animals against some of the principal microbial 

 toxins, he demonstrated the existence of specific antitoxins in their 

 body fluids. 



This very unexpected conception of antitoxins at once took root 

 in science, for it has been possible, thanks especially to the remark- 

 able works of Ehrlich, to extend it to toxins of non-microbial origin. 

 We are already acquainted with a certain number of antitoxins 

 which, however, are not comparable in number to the other 

 antibodies. Amongst these, the fixatives have many points of 

 analogy with the antitoxins. Like them, they are resistant to heat : 

 they exhibit also a fairly marked specificity, and, like the fixatives, 

 they are distributed in the plasmas. 



In the presence of so many points of similarity with the fixatives, 

 one is tempted to attribute to the two categories of antibodies the 

 same origin. The elaboration of antitoxins by tlie phagocytic 

 elements, accumulated in the blood and disseminated in the organs, 

 appears, in fact, to be very probable. Certain facts bearing on 

 the absorption of various toxins by the leucocytes, as well as tlie 

 distribution of antitoxins in the animal body, speak in favour of 

 this view. On the other hand, the impossibility of attributing the 

 ehxbomtion of antitoxins to cells attacked by the corresponding 

 toxins is quite in harmony with the same hypothesis. This hypo- 

 thesis is especially supported by the numerous facts which prove the [586] 



36 



