The effective duration of the delay phenomenon in the rat.

In standard skin flaps in the rat, the effect of a delay was undetectable for the first 3 weeks and the maximum benefit was not apparent until the sixth week. At all time intervals the delay phenomenon was not as pronounced in the rat as in other species. The delay phenomenon in the rat lasts at least 30 weeks. The rat does not appear to be an ideal model for the study of skin flaps.