254 ON VARIABILITY AND ADAPTATION 



Anaphylaxis 



If I may judge from the answers received recently from 

 the candidates for Dominion Medical Registration, anaphylaxis is 

 evidently regarded by the majority as one of those subjects that 

 no fellow can be expected to understand ; and addressing a general 

 medical audience it is essential to describe its broad phenomena. 

 Briefly, then, whereas, as everybody knows, the introduction of 

 foreign proteins into the economy is in general followed by the 

 development of immunity, the system gaining the power of 

 rendering harmless many times the fatal dose of that protein, 

 it is found that, employing minute doses of the protein for the 

 first injection, if now, at the end of a week or ten days a second 

 dose be injected, larger than the first, but still many times less 

 than that producing serious symptoms on first injection, then 

 instead of showing evidences of immunity, on the contrary the 

 animal has become hypersensitive. It may, indeed, die within 

 three to five minutes. In the guinea-pig, which shows most 

 strikingly these phenomena, there is an intense contraction of 

 the muscular walls of the bronchi, whereby dyspnoea is brought 

 about, with overfilling of the lungs so extreme that even when 

 the chest wall is freely cut open immediately after death, the 

 lungs remain expanded. With this there are muscular cramps 

 and obstruction to the onflow of blood with capillary congestion 

 leading to scattered haemorrhages. This state can be induced 

 by inoculation of any foreign protein, even one ordinarily so 

 harmless as egg albumen, or, on the other hand, by the employ- 

 ment of pathogenic bacteria and their proteid products. 



Now, here is the significant point. The symptoms and lesions 

 produced by the poisonous moiety of split protein are, as Vaughan 

 was the first to point out, identical with those seen in anaphylaxis. 

 In other words, anaphylaxis is due to the sudden setting free 

 in the economy of poisonous bodies of the same nature as the 

 poisonous disintegration moiety of proteins. On the doctrine, 

 therefore, that like results are produced by like substances, we 

 arrive at the conclusion that this hypersensitiveness or ana- 

 phylaxis is essentially due to a disintegration of the introduced 

 proteins with rapid liberation of the poisonous moiety. 



But the first dose introduced sets up none of these phenomena, 

 the second does. It is obvious that, following upon the intro- 



