100 



R. E. BILLINGHAM AND WILLYS K. SILVERS 



these grafts, which healed-in remarkably well in view of the 

 adverse grafting method employed. 



Since the layers of homologous areolar connective tissue 

 employed were by no means acellular, it seemed important to 

 determine whether their viability was essential for them to 

 *' protect" the overlays of homologous normal skin. Accord- 

 ingly, a series of sheets of freshly excised pouch skin were 

 repeatedly frozen and thawed under conditions deemed most 

 likely to kill the cells — i.e., very rap /W freezing to — 79° folio wed by 

 5/oif^ thawing (Billingham and Medawar, 1952). Evidence of the 



hos^ skin 



skin Komo(^raft 



layer cf homologous d»€ek pouc 

 connective tissue 



Fig. 5. Showing the method of grafting homologous skin upon a layer 

 of areolar connective tissue obtained from cheek pouch skin. 



effectiveness of this treatment was provided by the failure of 

 grafts of pouch skin or normal skin, which had been frozen and 

 thawed three times, to give evidence of survival on transplantation 

 to isologous hamsters. When sheets of areolar connective tissue 

 from "devitalized" homologous pouch skin were interposed 

 between ear skin homografts and their beds a considerable degree 

 of prolongation of their survival again resulted. 



As might be anticipated, healthy-looking, long-established 

 central inlay skin homografts in established pouch grafts, or skin 

 homografts overlying sheets of areolar connective tissue, were 

 fully susceptible to states of sensitization elicited in their hosts by 

 proxy (e.g. by intravenous injection of homologous leucocytes), 



