INTERACTION BETWEEN ANTIGEN AND ANTIBODY 157 



Nature of Anaphylactic Toxin. Regarding the nature of the ana- 

 phylactic poison, our knowledge is as yet quite meager. If we 

 regard the action of the amboceptor-complement combination upon 

 the albuminous antigen as comparable to the digestion of proteins 

 by the digestive ferments of the gastro-intestinal tract, in other 

 words, as a parenteral digestion, then we can also suppose that the 

 anaphylactic poison represents some cleavage product of the protein 

 molecule. As a matter of fact, there is a certain similarity between 

 the symptoms of the anaphylactic shock in dogs and what we see in 

 "peptone" poisoning in the same animal. In both instances there 

 is a marked drop in blood-pressure, incoagulability of the blood and 

 leukopenia, and in both cases it is possible to counteract the poison- 

 ous effect by the administration of barium chloride. In other 

 animals, however, such as the guinea-pig, "peptone" apparently 

 plays little or no role; Witte peptone, indeed, is quite harmless for this 

 animal, which, after all, is the most sensitive to anaphylactic shock. 

 Barium chloride, moreover, does not prevent the latter, and a primary 

 drop in blood-pressure, such as we see in dogs, does not occur. But 

 it is conceivable that while "peptone" does not play an important 

 role, if indeed any, that other poisonous substances may be formed 

 which may be quite harmless for the dog, but highly toxic for the 

 guinea-pig. 



Whether or not the anaphylactic poisons w r hich are split off from 

 different antigens by the antiserum of a given animal or animal 

 species are identical is unknown, but does not seem unlikely in 

 view of the uniformity of the anaphylactic symptom complex. 



In speaking of the anaphylactic poison in the foregoing pages 

 we have repeatedly made use of the term anaphylatoxin, which 

 has come into common use so extensively that it would indeed be 

 difficult to replace it. This term, of course, suggests that the poison 

 actually belongs to the class of toxins which, as we have seen, are 

 characterized by the fact that on immunization they give rise to 

 a corresponding antitoxin. As yet there is no evidence, however, 

 to show that it is possible to immunize against this poison, and it 

 would accordingly be better not to use the term anaphylatoxin at 

 all, or, if so, to bear in mind that by " toxin" in this case we merely 

 mean a poison in the more general sense of the word. 



Seat of Interaction between Antigen and Antibody. While in the 

 past it seems to have been assumed by the majority of observers 



