Touch

Touch. The sense of touch is usually said to include what is known as ordinary tactile sensibility, the sense of pressure, the sense of temperature, and pain. Tactile sensibility is possessed in greater or less degree by all parts of the skin. In some places, e.g. over the heel (where the epidermis is very thick), the tactile sense is dull; while in other parts, such as the tips of the fingers, and particularly the tip of the tongue, it is much more acute. In some instances certain end-organs of nerves appear to be concerned in transmitting tactile sensations. Such special end-organs have been already alluded to under the heading NERVE. In other instances no such special organs can be detected, the nerve-fibres simply breaking up at their terminations into a plexus of fibrillae. In estimating the degree of tactile sensibility of different parts of the body it is customary to ascertain the least distance at which the two points of a pair of compasses can be separately distinguished. This distance in the case of the tip of the tongue does not exceed 1/24 of an inch, while in the middle of the back it is as much as 2~1/2 inches.