EN 
THE COMMON INTEGUMENT 885 
the openings of the cutaneous glands and the hair-follicles, and its deep surface is 
adapted to the corium.! It is divisible into a superficial, harder, drier part, the 
stratum corneum, and a deeper, softer, moister part, the stratum germinativum. 
The cells of the latter contain pigment, and by their proliferation compensate the 
loss by desquamation of the superficial part of the stratum corneum. In many 
places further subdivision into strata is evident on properly prepared cross-sections. 
The corium consists essentially of a feltwork of white and elastic fibers. It is well 
supplied with vessels and nerves, and contain the cutaneous glands, the hair-fol- 
licles, and unstriped muscle. The deeper part of the corium, the tunica propria, 
consists of a relatively loose network of coarse bundles of fibers, and in most places 
there is no clear line of demarcation between it and the subcutis. The superficial 
part, the corpus papillare, is of finer texture and is free from fat. Its superficial 
face is thickly beset with blunt conical prominences, the papillae, which are received 
into corresponding depressions of the epidermis. They contain vascular loops and 
nerves, or, in certain situations, special nerve-endings.” 
The glands of the skin (Glandule cutis) are chiefly of two kinds, sudoriferous 
and sebaceous. The sudoriferous or sweat glands (Glandule sudoriferee) consist 
of a tube, the lower, secretory part of which is coiled in the deep part of the corium 
or in the subcutis to form a round or oval ball (Corpus glandule sudoriferee). The 
excretory duct (Ductus sudoriferus) passes almost straight up through the corium, 
but pursues a more or less flexuous course through the epidermis, and opens into a 
hair-follicle or by a funnel-shaped pore (Porus sudoriferus) on the surface of the 
skin. The sebaceous glands (Glandule sebacez) are in great part associated with 
the hairs, into the follicles of which they open. Their size varies widely, and is 
in general in inverse ratio to that of the hair. The larger ones are easily seen with 
the naked eye, and appear as small, pale yellow or brownish bodies. In certain 
situations (e. g., the labia, vulve, anus, prepuce) they are independent of the hairs 
and are well developed. In form they may be branched alveolar, simple alveolar, 
or even tubular in type. They secrete a fatty substance, the sebum cutaneum, 
which serves as a protective against moisture, and may also (by its aromatic con- 
stituents) play an important part in the sexual life of animals. 
The two kinds of glands described above are those which are most widely distributed, but 
many special types occur. Some of these are to be regarded as modified sweat glands, e. g., the 
naso-labial glands of the ox, the glands of the snout of the pig, and the glands of the digital 
cushion of the horse. Others, e. g., the tarsal glands of the eyelids, are modified sebaceous. Still 
others are not yet classified satisfactorily. Some of these special types have been referred to in 
previous chapters, and others will receive attention in the special descriptions which follow. The 
mammary glands are highly modified cutaneous glands, which are intimately associated in func- 
tion with the genital organs, and have been described with the latter. 
Vessels and Nerves.—The arteries of the skin enter from the subcutis, where 
they communicate freely. In the deeper part of the corium they form a plexus, 
and another network is formed under the papillae. Small vessels from the deep 
plexus go to the fat and sweat glands, and the subpapillary plexus sends fine 
branches to the papillee, hair-follicles, and sebaceous glands. The veins form two 
plexuses, one beneath the papilla, and another at the junction of the corium and 
subcutis. The lymph vessels form subpapillary and subcutaneous plexuses. 
The nerves vary widely in number in different parts of the skin. The terminal 
fibers either end free in the epidermis and in certain parts of the cortum, or form 
special microscopic corpuscles of several kinds. 
‘To prevent a possible misapprehension, it may be stated that the epidermis primarily 
molds the corium, and that the glands and hair-follicles are invaginations of the epidermis. 
2 The papille are best developed where the epidermis is thick and hairs are small or absent. 
On thickly haired regions they are small or even absent. On certain parts of the body (anus, 
vulva, prepuce, scrotum, eyelids, etc.) the corium contains pigment in its connective-tissue cells. 
