94 R. E. BILLINGHAM AND WILLYS K. SILVERS 



by a loss of 2-4 mm. in diameter. Further contracture did not 

 occur subsequently. 



(2) The fate of cheek pouch skin homografts 



The survival times of pouch skin homografts transplanted 

 between normal adult members of our strains are summarized in 

 Table II. Although with each combination some of the homo- 

 grafts were rejected quite promptly as a consequence of typical 

 acute reactions, the majority survived at least twice as long as 



Table II 



Survival times of homografts of cheek pouch skin exchanged between 

 adult hamsters of different strains 



Number of grafts alive on 



Strain Number of looth 



combination animals grafted 20th day 20th day 40th day soth day day* 



C.B.->M.H.A. 94 61(65%) 39(41%) 35(37%) 29(31%) 21% 



C.B.-^L.S.H. 50 36 (72%) 34 (68%) 33 (66%) 26 (52%) 52% 



L.S.H.^C.B. 51 40 (78%) 26 (51%) 24 (47%) 21 (41%) 35% 



* The percentages of grafts alive on the lOOth post-operative day are based upon 

 long-term observations of fairly small groups of animals. 



homografts of ordinary skin of similar genetic origin (see Table I), 

 and an appreciable proportion survived in a perfectly healthy, 

 "isograft-like" condition for as long as their hosts remained under 

 observation — more than 200 days in some cases (see Figs, i and 2). 

 The long-delayed rejection of some of the hitherto healthy- 

 looking homografts took place fairly rapidly, within about 7-14 

 days of the appearance of adverse signs, such as oedema, intra- 

 dermal haemorrhages, and epithelial weakness or ulceration. 

 With other pouch skin homografts that long outlived control 

 skin homografts, rejection was of the drawn-out or chronic type, 

 in which epithelial desquamation, minor scabbing and epithelial 

 weakness with partial recovery, and progressive contracture, to 



