THE MECHANISM OF IMMUNITY 91 



the first to show that every true protein when digested 

 with several times its bulk of absolute alcohol in the pre- 

 sence of 2 per cent of sodium hydroxide, splits up into a poison- 

 ous and a non-poisonous moiety, the former soluble in alcohol, 

 the latter insoluble. The poisonous moiety, when introduced 

 into the system by any path other than through the alimentary 

 canal, is rapidly fatal in relatively minute doses, setting up 

 symptoms identical with those seen in the anaphylactic stage. 

 I have pointed out (p. 38) that anaphylaxis, or hypersuscepti- 

 bility, is the first phase in the production of immunity. On the 

 principle, therefore, that like results are produced by like sub- 

 stances we arrive at the conclusion that this hypersensitiveness 

 or anaphylaxis is essentially due to the disintegration of the intro- 

 duced proteins with rapid liberation of the poisonous moiety. 



But the first dose of a foreign protein introduced into the 

 tissues sets up none of the phenomena, the second does. 

 Evidently in the course of the few days necessary for anaphylactic 

 phenomena to manifest themselves the organism has gained a 

 new power, that of splitting up the foreign protein. Abderhalden 

 demonstrated the first stages in this process. In 1910 he and 

 his pupils published a remarkable series of " Serological studies 

 by means of the optical method." Starting from the fact that 

 the different proteins and peptones, when in suspension, present 

 each in the polariscope a specific index of rotation, he demon- 

 strated first that enteral digestion of proteins, i.e. the introduc- 

 tion of the same through the intestinal tract, has absolutely no 

 effect upon the physical condition of the blood serum : its 

 rotatory power is unaltered. But parenteral injection of any of 

 the more common proteins, i.e. by the subcutaneous or intra- 

 venous route, leads to a very different state of affairs : the index 

 of rotation of the removed blood plasma undergoes progressive 

 alteration, a clear indication that the protein is being broken 

 down, and this is confirmed by the fact that by dialysis peptones 

 can be separated off from the plasma. 



Within forty-eight hours, therefore, after the introduction 

 of a foreign protein, the system has responded either by elaborat- 

 ing a proteoclastic enzyme, or, it may be, by a rapid increase 

 in the production and discharge of already existing proteoclastic 

 enzyme present in certain cells. But what I would particularly 

 emphasize is that in this first phase the enzyme is not specific. 



