HAMSTER CHEEK POUCH SKIN HOMOGRAFTS 93 



side of the pouch resulted in a more or less flat sheet of skin which 

 was immersed in normal sahne solution, containing 150,000 units 

 of penicillin and 125 mg. dihydrostreptomycin sulphate in 

 suspension/ ml., for about 30 minutes as a prophylactic measure. 

 The slight swelling of the connective tissue which occurred in this 

 medium facilitated trimming off excess areolar tissue necessary 

 to ensure prompt healing after transplantation. Circular grafts, 

 usually about 2 • 0-2 • 5 cm. in diameter, were then cut from areas 

 of pouch skin in which muscle fibres were absent. 



The grafts were transplanted to beds of appropriate size 

 prepared in the skin of the side of the hosts' chests according to 

 our standard procedure for grafting normal skin (see Billingham, 

 1961). 



Experimental findings 

 (l) The fate of cheek pouch skin isografts 



To provide the necessary controls, 40 C.B. hamsters received 

 grafts of C.B. pouch skin which were maintained under observa- 

 tion for at least 60 days. Provided that the thickness of these 

 grafts was not excessive, they healed-in just as rapidly and 

 satisfactorily as isografts of appropriately trimmed normal skin 

 and no evidence of immunological rejection was obtained. As 

 anticipated, these pouch skin grafts conserved their anatomically 

 distinctive features. They remained highly vascular, being flush 

 pink in colour, and their hairless epithelial surface usually displayed 

 a characteristic pattern of fme ridges or corrugations. Further- 

 more, they were covered with thin semi-transparent cuticular 

 layers which peeled off easily and were promptly regenerated — 

 indirect evidence of a chronic high rate of mitotic activity in the 

 epidermis. 



Comparison of the diameters of these grafts two weeks after 

 transplantation, when primary healing was complete, with their 

 diameters after they had been in residence for 50 days indicated 

 that most of them had undergone slight contracture, as evidenced 



