Cutaneous or skin sensation may arise from either _mechanical_

stimulation, such as pressure, a blow, or tickling, from _thermal_
stimulation from hot or cold objects, from _electrical_ stimulation, or
from the action of certain _chemicals_, such as acids and the like
Cutaneous or skin sensation may arise from either _mechanical_
stimulation, such as pressure, a blow, or tickling, from _thermal_
stimulation from hot or cold objects, from _electrical_ stimulation, or
from the action of certain _chemicals_, such as acids and the like.
Stimulated mechanically, the skin gives us but two sensation qualities,
_pressure_ and _pain_. Many of the qualities which we commonly ascribe
to the skin sensations are really a complex of cutaneous and muscular
sensations. _Contact_ is light pressure. _Hardness_ and _softness_
depend on the intensity of the pressure. _Roughness_ and _smoothness_
arise from interrupted and continuous pressure, respectively, and
require movement over the rough or smooth surface. _Touch_ depends on
pressure accompanied by the muscular sensations involved in the
movements connected with the act. Pain is clearly a different sensation
from pressure; but any of the cutaneous or muscular sensations may, by
excessive stimulation, be made to pass over into pain. All parts of the
skin are sensitive to pressure and pain; but certain parts, like the
finger tips, and the tip of the tongue, are more highly sensitive than
others. The skin varies also in its sensitivity to _heat_ and _cold_. If
we take a hot or a very cold pencil point and pass it rather lightly and
slowly over the skin, it is easy to discover certain spots from which a
sensation of warmth or of cold flashes out. In this way it is possible
to locate the end-organs of temperature very accurately.


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