ADAPTATION OF CUTANEOUS TACTILE RECEPTORS. III

Further experimental evidence is presented indicating that the peripheral inhibitory phenomenon known as sensory adaptation, as it is manifested in tactile receptors in frogs' skin, is produced by a neurohumor released by non-nervous cells of the skin when they are pressed upon. 1. Adaptation is not produced by electrically initiated antidromic impulses backfired into the axon branches. 2. Intermittent air jet stimulation of a region of skin several millimeters distant from a responsive single ending produces failure of response of the ending to a similar direct intermittent stimulus applied to the skin containing the ending immediately afterward. 3. Constant pressure causes an ending to adapt but no spread of the effect, as described in the above paragraph, is found. This implies that the spread is the result of the vibratory movement of the skin. 4. The time curves of recovery from adaptation are inconsistent with any known properties of isolated nerve.