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626. Where do the nerves of the skin proceed from? Are they numerous
in this membrane? How is it proved? What is said of those parts most
exposed to injury? Give example 1st. Example 2d. 627. Mention the
difference in the distribution of the nerves in various parts of the
body. Is this difference found in the lower order of animals?

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628. In the small papillae, the nerve forms a single loop, while in
papillae of larger size, and endowed with a power of more exalted
sensation, the nerve is bent several times upon itself previous to
completing the loop. These little loops spring from a net-work of
nerves, imbedded in the upper porous layer of the true skin, at the
base of the papillae. This net-work of nerves receives its influence
through nerves which take their winding course through the fat
distended openings of the deeper layers of the true skin.

[Illustration: Fig. 113. 1, 1, The cuticle. 2, 2, The colored layer of
the cuticle. 3, 3, The papillary layer, exhibiting the nerves as they
form loops. 4, 4, The net-work of nerves. 5, 5, The true skin. 6, 6, 6,
Three nerves that divide to form the net-work (4, 4.) 7, 7, 7, The
furrows between the papillae. 8, 8, 8, Three papillae magnified fifty
diameters.]

629. The LYMPHATICS are found in great numbers in the true skin, and
they are so minute that they cannot be seen with the naked eye; but
when these hair-like vessels are injected with quicksilver, (a work of
great difficulty,) the surface injected resembles a sheet of silver.
In this way their existence can be imperfectly demonstrated. They are
a part of the vascular net-work situated upon the upper surface of the
true skin. Each papilla is supplied with a lymphatic filament, the
mouth of which opens beneath, and lies in contact with the under
surface of the cuticle. This net-work of vessels communicates through
the open meshes of the true skin with larger lymphatic trunks, that
open into the venous system.

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628. How are the nerves of the small papillae arranged? How in the
large papillae? What does fig. 113 represent? 629. What is said of the
cutaneous lymphatics? How is their existence proved?

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[Illustration: Fig. 114. A plexus of lymphatic vessels in the skin,
considerably magnified from an injected preparation.]

630. The OIL-GLANDS are small bodies imbedded in the true skin. They
connect with the surface of the s