THEORIES OF ANAPHYLAXIS 203 



the anaesthetic renders the nerve cells insensitive to the 

 reaction between the sensibilisin and anti-sen sibilisin. 



According to Richet, a " toxigen " is formed in the 

 blood or cells at the end of the incubation period and 

 persists for a long period. A toxic apotoxiii or precipitin 

 is formed as a result of the interaction of toxigen with 

 antigen, the toxicity of which is further increased by 

 combination with the alexin of the blood. 



Bordet suggests that the union of anti-body and antigen 

 creates a complex which by adsorption monopolises 

 certain principles in the blood plasma which then becomes 

 toxic. Thus Wassermann and Reysser found that if 

 guinea-pig serum and kaolin, an inert powder, be mixed 

 and then centrifuged, the intravenous injection of the 

 fluid is followed by symptoms closely resembling those 

 of anaphylaxis. A weak agar jelly (0-05 per cent.) acts 

 similarly. The serum must be fresh and active ; serum 

 heated to 56 C. is inert. It is doubtful, however, whether 

 colloids do produce typical anaphylactic death ; when 

 death occurs it is probably due to intravascular clotting. 



A remarkable feature of anaphylactic shock is the 

 almost complete disappearance of complement, but this is 

 not the immediate cause of the condition. Friedberger 

 found that complement is able to form from antigen a 

 toxic body which on injection into a normal animal gives 

 rise to all the phenomena of anaphylactic shock. But 

 while complement alone is capable of effecting this change 

 to a certain extent, the toxic product appears far more 

 rapidly and in much greater quantity if the specific anti- 

 body be present as well. The condition necessary for 

 maximum toxicity, i.e. for the formation of the largest 

 amount of anaphylatoxin, depends upon three factors : 

 (a) the relative quantities of complement, anti-body and 

 antigen present together, (b) the time during which these 

 substances interact, and (c) the temperature at which 



