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THE SKIN. 145

parts of the body, beino; largest on the pahuar surfaces of the hands and
the soles of the leet. These papillae of the true derm fit into correspond-
ing depressions of the epiderm. As the superior surface of the papillary
layer is approached the fibrous network of the connective and the elastic
tissue becomes finer and finer, the fibres approximating more closely until
they appear to form a homogeneous layer known as the basement mem-
brane of Todd and Bowman.
The fibres toward the inferior surface of the papillary layer are
coarser and more loosely interwoven than they are at the superior sur-
face, and finally pass into the subareolar tissue.
l^he Reticidar Layer.—The line of demarcation between the upper
and the lower layers of the true skin is not clear and distinct, but one
part gradually merges into the other, the principal point of difference
being in the arrangement of the fibrous network. Descending from
above, the fibres become fewer and are situated farther apart, until a
coarse network is formed, which is finally lost in the subcutaneous con-
nective tissue. At this point these bands form a loose reticulum, the
meshes of which are generally filled Mith an abundance of fat.
The quantity of fat within the reticulum varies considerably in dif-
ferent regions of the body, being large about the mammary glands and
in the palms of the hands and the soles of the feet, while in the eye-
lids and about the ears but little if any is found.
The Blood-vessels of the Skin ascend through the subcutaneous con-
nective tissue, and divide as they pass through the true derm toward
the surface. They give off branches which pass to the fat-clusters,
sweat-glands, hair-follicles, and the corium. As they approach the
papillary layer they form a fine capillary network of anastomosing
vessels, the papillae being supplied with capillary vessels Avhich pass
through their central portion, furnishing an abundant supply of blood.
Veins accompany the arteries in their ramifications, but no blood-ves-
sels pass into the epiderm.
The Lymphatics are distributed throughout the entire surface of the
skin, except the epidermal layer, though not equally in all parts, being
larger and more abundant around the nipples and on the scrotum.
They are arranged in two strata, with anastomosing vessels between
them. The superior stratum is situated just below the network of
capillary blood-vessels, passing up into some of the papilla3 in the
palms of the hands and soles of the feet. Valves are found in the
larger vessels of the corium, but not in the smaller ones or in those
of the superior layer. The hair-follicles and the glands of the skin have
special plexuses of lymphatics as well as of blood-vessels.
The lymphatics of the skin orginate in the spaces between the cells,
as they do in other kinds of connective tissue, and have a linear arrange-
ment between the bundles of fibres.
The Nerves.—As the skin is the organ of the body possessing the
is but natural to expect many
special function of touch-perception, it
nerves to be distributed over its surface ; and as the degree of sensi-
bility varies, it is also to be supposed that the nerves are not equally
distributed. The principal branches pass through the subcutaneous
connective tissue, divide at the corium, and run in various directions,
Vol. I.—10