Figure 4. Cell survival curves for colonies in pig epidermis containing 16 bromodeoxyuridine-positive cells at different times after various levels of irradiation. ^____, Frequent biopsying of different skin fields in the same animals over a short period of time after irradiation; ----, biopsying of all skin fields simultaneously after irradiation. Three different levels, ED₂₀, ED₅₀ and ED₈₀, for the incidence of moist desquamation as obtained from an in vivo study are indicated for comparison.