Schematic drawing of excised skin mounted in the Franz cell diffusion system. The donor chamber (1) above the skin contains the applied topical agent. The chamber below the skin is the receptor chamber (2) from which samples are taken through the sampling port. The receptor chamber is surrounded by a water jacket (3) maintained at 32 °C. A magnetic stirrer and stirring helix are magnetically rotated at the bottom of the receptor chamber. The topical drug, which is applied to the stratum corneum side of the skin, permeates into the dermis side and then crosses the skin.