The Sense of Touch.
The nerves of the sense of touch have their ending in the outer covering or skin of the body. They report contact with other physical objects. By means of these reports we are aware not only of contact with the outside object, but also of many facts concerning the nature of that object, as for instance, its degree of hardness, roughness, etc., and its temperature. Some of these nerve ends are very sensitive, as, for example, those of the tip of the tongue and finger ends, while others are comparatively lacking in sensitiveness, as, for illustration, those of the back. Certain of these sensory nerves confine themselves to reporting contact and degrees of pressure, while others concern themselves solely with reporting the degrees of temperature of the objects with which their ends come in contact. Some of the latter respond to the higher degrees of heat, while others respond only to the lower degrees of cold. The nerves of certain parts of the body respond more readily and distinctly to temperature than do those of other parts. To illustrate, the nerves of the cheek are quite responsive to heat impressions.