﻿MODERN THEORIES IN RELATION TO IMMUNITY. 77 



cells destroyed should draw our attention to the phenomenon of catalysis. 

 The study of catalysis and of catalytic reactions has been advanced most 

 markedly within the past few years, and we have come to have a much 

 clearer conception of the principles underlying the changes brought about 

 by catalytic agents than we formerly had. One fundamental fact must 

 always clearly be borne in mind, and that is the catalyzer can not change 

 the end equilibrium of a reaction, it can only alter its rate. A simple 

 example will suffice. If we have a mixture of hydrogen and oxygen, 

 the two gases apparently do not unite at ordinary temperatures, some 

 infinitesimal union however does take place with the formation of water, 

 but the rate of reaction is too slow, to be measured and it must be derived 

 by interpolation after a study of the change at higher temperatures. 

 However, if the mixture of gases were to remain for a sufficient length 

 of time, centuries in this instance, a final end equilibrium, in which nearly 

 all had been changed to water and but infinitesimal traces of hydrogen 

 and oxygen would remain, would finally be realized. The introduction 

 of a catalyzer, in this case let us say platinum sponge, will so alter the 

 rate of reaction that it may even proceed with explosive violence, a few 

 seconds sufficing to accomplish that which would take ages under ordi- 

 nary circumstances. The catalyzer itself, however, is not altered. The 

 recent work of Bredig on the colloidal metals has furnished us with 

 a series of inorganic catalyzers which have the remarkable property of 

 being "poisoned" by chemical reagents similar to those which attack 

 the organic enzymes, and even without such a hint as to a possible 

 resemblance between the inorganic colloids and the organic enzymes, 

 it is quite generally believed that the enzymes are specific organic cata- 

 lyzers with the power of accelerating the rate of normal reactions which 

 otherwise might be infinitely slow. 



The theor}'' of Ehrlich, very briefly stated, is as follows : A cell, having 

 certain chemical groups, is introduced into a body. If, in any of the 

 multitudinous cells of that body there is one which has chemical groups 

 capable of uniting with those of the introduced cell, then, on contact, 

 such union takes place. The attacked cell in the living organism, having 

 its equilibrium disturbed by the occupation of one of its chemical groups, 

 proliferates others whicb, as I will show further on, may or may not 

 be of the same nature and which are thrown off into the circulation. The 

 proliferated chemical substance must be capable of attaching itself to 

 an albuminous molecule of the introduced cell, for it contains the 

 chemical grouping which assumed the original function of binding 

 the introduced cell. But, in itself, this detached group is not able to 

 bring about the destruction of the foreign invader, it must be rendered 

 capable of so doing by uniting with a chemical substance present in the 

 blood plasma, which is termed the complement. The immune body which 

 is proliferated therefore is an amboceptor, with one group it is capable of 



