24.8 MICROBES AND TOXINS 



so, because being partly coagulated its fixation is delayed. 

 The action of serum, sensitizing, vaccinating, or toxic, depends 

 thus on its physical condition. 



There are therefore really only two activities of serum 

 in question, that of the antigen and that of the antibody. But 

 according to its physical condition, according to the manner 

 and time of its injection, the antigen plays the part of sensitizer, 

 of vaccinator or of toxin. These explanations, it must be 

 mentioned, are confined to the field of serum-anaphylaxis as it 

 is known to-day. 



We always return thus to the antigen and the antibody, i.e., to 

 the activities which we found to exist in all the phenomena of 

 immunity. 



General Theory of the Antibodies. — M. Nicolle has 

 proposed a general explanation embracing anaphylaxis as a 

 particular case of the general physiology of the antibodies. 

 Every antigen induces in the body the simultaneous formation 

 of antibodies of two classes, the coagulins and the lysins. The 

 coagulins condense albuminoids and toxins (to speak only 

 of these two varieties of antigen) ; the lysins, on the contrary, 

 break them up and liberate from them their real toxic 

 components : ^ in intoxication by proteid poisons it is not these 

 themselves which injure the body, but secondary poisons 

 elaborated by it itself. The fate of the animal depends on its 

 species, on the nature and quantity of the antigen, on the 

 channel of inoculation and on the route by which the assaulting 

 dose is introduced. 



Thus, in the phenomenon of Th. Smith, the supersensitive- 

 ness is explained by the development of a lysin and the 

 absence of all coagulin makes of it the type example of pure 

 supersensitiveness. In bacterial anaphylaxis, the super- 



^ When the coagulins predominate they rapidly condense the antigens, 

 giving the body time to attack them bit by bit without liberating enough 

 poison at a given moment to cause toxic or, at least, fatal symptoms. The 

 lysins on the contrary, when they predominate, make their appearance as 

 the agents of an inevitable and often fulminating intoxication, for the body 

 has only limited protection against the true endotoxins and the true toxins, 

 no more than it has against alkaloids, for example " (Nicolle). 



