THE UNIQUENESS OF THE INDIVIDUAL 



at the temperature of liquid air or carbon dioxide snow. The 

 difficulty is that a skin graft from one human being will not 

 form a permanent graft upon the body of another. In the first 

 week or so after its transplantation the homograft (as it is 

 called) behaves just like a graft which has merely been trans- 

 posed from one part to another of a single individual. The first 

 outward sign that all is not well is a puffiness and inflammation 

 of the grafted skin, leading to a weakening and ulceration of 

 its surface, and finally to abject necrosis followed by a slough- 

 ing away. How soon this happens — perhaps after only ten days, 

 perhaps in a month — depends upon a number of variables, 

 some of which I shall mention below. Every now and again a 

 homograft lasts long enough to make a surgeon begin to hope 

 that a natural law is about to be suspended in his favour, but 

 sooner or later (and the general rule is sooner rather than later) 

 the graft withers up and disappears. A human being is resol- 

 utely intolerant of skin grafted upon him from other members 

 of his own species; so is a newt, chicken, mouse or cow; nor will 

 even a goldfish accept a scale from any other.^ The problem 

 of how this comes about, why it should be so, and what can be 

 done about it is the subject of the present article. 



2. RULES AND EXCEPTIONS 



The idea that homografts of skin are invariably destroyed 

 within a few weeks of their transplantation, so that they are 

 useless for anything except avowedly temporary repair, is now 

 accepted by all well-informed surgeons, though recognition of 

 the truth was slowly and hardly won. I now wish to consider 

 three exceptions to this general rule, two of them predictable 

 and perfectly intelligible, the third of a surprising and entirely 

 unexpected kind. 



The first exception is that skin and other tissues can be 



1 W. H. Hildemann, Proc. N. Y. Acad. Sci., 1957. 



146 



