The calluses developed by people who use their hands professionally constitute a particular case of localized touch. In principle the thickened layer of skin should deaden touch; in practice, the reverse occurs. By protecting the nerve endings in the hand, the callus makes the act of probing less hesitant. Although the physiology of this process is not yet well understood, the result is: the callus both sensitizes the hand to minute physical spaces and stimulates the sensation at the fingertips.
