SUPEKSENSITIVENESS OK ANAPHYLAXIS 595 



very important part. It has been shown by Muir and Browning 

 by means of hsemoly tic tests that the toxic activity of complement, 

 after it has been fixed to the corpuscles, varies very much ; in some 

 instances an amount of complement, which would rapidly produce 

 complete lysis of one kind of corpuscle, may have practically no 

 effect on another, even though it enters into combination. These 

 results are of importance in demonstrating how the corresponding 

 cells of different animals may vary in sensitiveness to toxic action. 



Supersensitiveness or Anaphylaxis. 



Under this heading are to be grouped a number of phenomena 

 which in their character and results appear to present a striking 

 contrast to the state of immunity, yet in their essential nature are 

 probably closely allied to the latter condition. Like immunity, 

 supersensitiveness may be natwral or acquired. It has long been 

 recognised that the ingestion of certain substances, e.g., shell-fish, 

 strawberries, etc., by normal individuals is sometimes followed 

 by constitutional disturbances, and more recently it has been 

 found that in a small proportion of individuals the injection of 

 a small amount of foreign serum may give rise to constitutional 

 disturbances. There is therefore a natural supersensitiveness to 

 these substances. The greatest importance, however, from the 

 practical point of view, is in regard to acquired supersensitive- 

 ness in the process of serum treatment. The general fact is that 

 repeated injections of certain substances in sub-toxic or non- 

 toxic doses — a suitable interval of time elapsing between the 

 injections — may be followed by markedly toxic or even fatal 

 symptoms, and a similar result may follow repeated injections 

 of substances which are practically non-toxic in a single dose. 

 The substances which have been found to have the property of 

 calling forth this condition are of various kinds, including 

 bacteria and their toxins, animal poisons, and a great many 

 foreign proteins, e.g., those of serum, milk, egg albumin, etc., and 

 it is to be noted that they belong to the group of 'substances 

 which can act as antigens. Probably only proteins originate 

 supersensitiveness ; and, just as tolerance, say to drugs, is to be 

 distinguished from immunity, so accumulative action is to be 

 distinguished from supersensitiveness. Of the latter condition 

 the earliest example observed was probably the special suscepti- 

 bility of tubercular patients to the action of tuberculin, to which 

 reference has already been made (p. 290), and to this and like 

 conditions the term allergy is often applied. At a comparatively 

 early date also it was found, in the case of diphtheria and 



