Unstirred layers' in frog skin

1. Estimates of the magnitudes of the unstirred regions associated with isolated frog skin in sulphate Ringer's solution have been made under different stirring conditions. 2. The method of investigation was an analysis of the time course of the p.d. transients which occurred when external sodium concentration and internal potassium concentration changes were made in the bathing solution. 3. Making an arbitrary but reasonable assumption about the diffusional coefficient of Na 2 SO 4 in the outer unstirred region, the magnitudes of the outer unstirred layers were found to lie within the ranges 40-60 μ, 30-50 μ and 30-40 μ under stirring conditions of 120, 300 and 500 rev/min, respectively. 4. Making an arbitrary but reasonable assumption about the diffusion coefficient of K 2 SO 4 in the inner unstirred region, the magnitudes of the inner unstirred layers were found to lie within the ranges 150-230 μ, 120-200 μ and 100-170 μ under stirring conditions of 120, 300 and 500 rev/min, respectively.