﻿MODERN THEORIES IN RELATION TO IMMUNITY. 7 



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have been obliged to bring into their considerations conceptions which, 

 while using different terms, still in many respects conform to the position 

 assumed by Ehrlich. 



It is with much diffidence that I approach this subject as a chemist. 

 I had hoped when I selected this topic to have some experimental material 

 to bring before the association, but unfortunately my time has been 

 so occupied in other directions that I have been unable to accomplish 

 what I wished. It will therefore be necessary for you to take such discus- 

 sion as I have to give, for what it is worth. 



A merely casual consideration of the phenomena of immunity to 

 disease develops the fact that we encounter specialized resistance to 

 certain types not only in races, but in families, orders, genera, species 

 and even in individuals. By some processes in the development of various 

 groups of animals, some have become resistant to the change in their 

 condition brought about by the introduction of certain foreign cells, 

 others have become immune to other infections, and so on. This re- 

 sistance may manifest itself either in a destruction of the introduced 

 cells, in an impairment of their functions, or it may appear as a simple 

 tolerance to their presence without deleterious results. Of course, in 

 this connection we must also consider the cell which is introduced, this 

 too can hy ages of development have become resistant or tolerant to the 

 influences of certain of its hosts, and in this way may be capable 

 of resisting destruction in their bodies. The main question to be 

 considered is, How is this destruction or tolerance brought about? In 

 the case of the destruction of an introduced cell, this must either take 

 place by the action of some chemical groups or individuals present in 

 the host, by the aid of which the introduced cell is disintegrated and 

 dissolved, or it must be by physical means, by the action of some form 

 of energy by which chemical changes leading to the disintegration of the 

 cell are inaugurated in the latter. That a proper modification of energy 

 can bring about chemical reaction is too well known for discussion, but it 

 is diffieidt to conceive how an organism which has been produced while 

 subject to all various manifestations of energy which surround us, should, 

 upon being merely transferred to another organism which has also been 

 produced under the same general conditions, be destroyed by such means 

 only. It is true that in the phenomenon of agglutination we may have, at 

 first sight, some indications of the action of polarity, but here also, to 

 produce the change, certain specific chemical bodies must be present. A 

 change in energy undoubtedly takes place during the processes of cell des- 

 truction or agglutination and this change in energy must have further, 

 far-reaching results, but as yet the study of immunity has not advanced to 

 a sufficient degree to render a consideration of this phase possible. There 

 remains then as the most probable, a priori hypothesis the one which 

 assumes that the examples of cell destruction or agglutination which 



