need for the protection of the delicate vessels, nerves, viscera, and
muscles underneath. Undoubtedly it performs, and by its tough and elastic
texture is well fitted to perform, this extremely important service. But
the skin is not merely a method of protection against the external world;
it is also a method of bringing us into sensitive contact with the
external world. It is thus, as the organ of touch, the seat of the most
widely diffused sense we possess, and, moreover, the sense which is the
most ancient and fundamental of all--the mother of the other senses.

It is scarcely necessary to insist that the primitive nature of the
sensory function of the skin with the derivative nature of the other
senses, is a well ascertained and demonstrable fact. The lower we descend
in the animal scale, the more varied we find the functions of the skin to
be, and if in the higher animals much of the complexity has disappeared,
that is only because the specialization of the various skin regions into
distinct organs has rendered this complexity unnecessary. Even yet,
however, in man himself the skin still retains, in a more or less latent
condition, much of its varied and primary power, and the analysis of
pathological and even normal phenomena serves to bring these old powers
into clear light.

Woods Hutchinson (_Studies in Human and Comparative Pathology_,
1901, Chapters VII and VIII) has admirably set forth the immense
importance of the skin, as in the first place "a tissue which is
silk to the touch, the most exquisitely beautiful surface in the
universe to the eye, and yet a wall of adamant against hostile
attack. Impervious alike, by virtue of its wonderful responsive
vitality, to moisture and drought, cold and heat, electrical
changes, hostile bacteria, the most virulent of poisons and the
deadliest of gases, it is one of the real Wonders of the World.