THE UNIQUENESS OF THE INDIVIDUAL 



cortisone and other steroid hormones on the behaviour of 

 homografts, particularly in its recent developments by P. L. 

 Krohn, is giving us a new insight into the nature of the normal 

 adrenal cortical secretions, how they vary from members of one 

 species to another, and how they are influenced by the trophic 

 hormone of the pituitary gland. 



The weakening of an animaPs reaction against homografts 

 which can be brought about by the treatments or maltreat- 

 ments I have just described is simply a by-product of some 

 more general biological damage. The specific treatments I now 

 turn to are nicely discriminating in their action; they influence 

 the survival of homografts from particular donors chosen 

 beforehand, and have no efl'ect on other immunological re- 

 actions. One such treatment, the particular study of research 

 workers in the Roscoe B. Jackson laboratory at Bar Harbor, 

 Maine, entails the injection of the animals which are later to 

 receive homografts with desiccates or extracts made from the 

 tissues of their future donors. The theoretical importance of 

 this treatment outweighs its practical usefulness, v/hich by all 

 appearances is very modest, for the best it has been able to do 

 in our hands is to double or treble the normal expectation of 

 life of a skin homograft. Beyond the fact that it is certainly 

 immunological in character, there is no common agreement 

 about the way this treatment works. My colleagues and I are 

 inclined to interpret it as an interference with the normal 

 reaction against homografts which is somewhat analogous to 

 *'desensitization*' against an allergic state. Allergic symptoms 

 of the kind caused by, for example, pollen, are thought to be 

 due to the union of the pollen antigens with a peculiar and 

 unstable kind of antibody known as a *'reagin\ According to 

 one interpretation, which may be unduly simple, desensitiza- 

 tion consists in inducing the body to form orthodox and 

 inoff'ensive antibodies against pollen which, by getting in first, 

 cover or coat or otherwise preoccupy the pollen antigens so 



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