Like the nose
and tongue, the skin is a sense organ with many other functions. Covering
approximately 17 square feet of tangible surface in adults and weighing together about five pounds the skin is the largest single organ of the human body. It is
a vital organ. Destruction of a little more than one-third of the skin area, as
by burning or scalding, is usually fatal.
Clendening
speaks lyrically of the skin as "one of the most interesting and mystic of
structures." He calls it "that outer rampart which separates us from
the rest of the universe, the sack which contains that juice or essence which
is me or which is you, a moat defensive against insects, poisons, germs. The
very storms of the soul are recorded upon it."
The variety of
sensations recorded and reported to the brain by the skin is undoubtedly one
of the factors that make it so "interesting." Tactile sensation touch
is only one of five types of sensation to which the specific end-organs of the
skin respond. They can also be stimulated by pain, pressure, heat and cold, and
combinations of sensations. Pain, apparently, is registered by bare nerve
endings; but for each of the other sensations there are specific types of
end-organs, called corpuscles and discs. Meissner's corpuscles, located mainly
in the hairless parts of the skin, are the chief end-organs of the sense of
touch. They react individually to touch and collectively to pressure. Another
type of tactile sense organ surrounds the individual hairs on the skin. These
end-organs are highly responsive to the slightest movements of the hairs, such
as those caused by a light touch or a draft of air.
The end organs for touch are distributed unevenly on the total skin
surface of the body. Most sensitive areas are the lips and the tip of the
tongue. Fingertips are quite sensitive; back, arms, and legs much less so.
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