PRESIDENT S ADDRESS — ."^ECTION L. 283 



Two experimental methods have suggested themselves for deter- 

 mining this point. First, several workers have shown that after 

 anaphylactic shock the total amount of complement in an animal 

 was lessened, suggesting that some complement had been used up 

 in the reaction. 



Then, again, Loeffler (1910) employed a number of guinea pigs 

 which had been sensitized to horse serum. He injected intraperi- 

 toneally into some of them a sufficient quantity of sensitized 

 sheep's red cells as to use up all the complement possessed by the 

 animals, and then he injected a test dose of horse serum into all 

 of them one hour later. The guinea pigs whose complement had 

 been used up showed no anaphylaxis, whilst the control animals 

 showed typical shock and died. Thus, we may conclude that in 

 the ordinary anaphylactic reaction complement does share, being 

 adsorbed by the antigen-antibody combination as in other 

 immunity reactions. 



And now, what fli caries have been advanced to explain these 

 phenomena, in other words, what is the nature of anaphylaxis ? 

 As is to be expected in so complicated a subject of gradual 

 development, the theories are many, but at the present time it will 

 be sufficient to mention three or four. 



The processes of digestion of the proteins taken in as food so 

 modify them as to allow of the absorption of non-toxic substances 

 only, but injection of many of these substances into the blood 

 stream is highly dangerous. For example, commercial peptone, 

 given intravenously in the dog, j^roduces symptoms very similar 

 lo those of anaphylaxis. Further, it is well known that the injec- 

 tion of many substances, whether antigens proper or not, into the 

 blood stream brings about thei appearance of fennents, " defensive 

 ferments," as Abderhalden has called them, which break down 

 these abnormal bodies, and so' preserve the integrity of the blood. 

 An old observation of Delezenne's (1890) showed that the injection 

 of gelatin rendered the blood serum capable of liquefying gelatine 

 //( vitro. 



Acting on this knowledge, and having obtained highly toxic pro- 

 ducts from egg albumen and other proteins by purely chemical 

 means, Vaughan and Wheeler put forward the view that in active 

 anaphylaxis the first injection causes the production of protective 

 fennents in the blood, and that on the second injection of the 

 antigen these ferments bring about splitting cf it with liberation 

 of toxic substances which account for the symptoms. 



Against this view are the two facts that anaphylactic shock 

 often occurs with extraordinary suddenness, whereas ferment 

 action would take some time, and fui'ther the shock is a specific 

 reaction only produced by the injection of a specific antigen, the 

 same in origin and composition as the original antigen, whereas 

 a ferment would have no such specific selective action. 



