a 
728 THE SKIN OR INTEGUMENT. 
skin assumes a yellowish tinge in old age, while in certain diseases (e.g. icterus 
and melasma Addisoni1) it undergoes marked alteration. 
The surface of the skin is per rforated by the hair follicles and by the ducts of the 
sweat and sebaceous glands, and on the palms, soles, and flexor aspect of the digits 
it presents numerous permanent ridges (criste cutis), which correspond with rows 
of underlying papille. Over the terminal phalanges these ridges form distinctive 
patterns, w hon are retained from youth to old age, and may be utilised for 
purposes of identification. Folds of the skin (re tinacula cutis) are seen in the 
neighbourhood of the joints, and it can be thrown into wrinkles by the contraction 
of the subcutaneous muscles, where these exist. Over the greater part of the body 
it is freely movable; but on the scalp and outer surface of the pinna, as well as on 
the palms and soles, it is bound down to the subjacent tissues. 
The skin consists of two strata, viz.: a deep, termed the dermis or corium, and 
a superficial, named the epidermis (Fig. 536). 
The corium gives elasticity and sensibility to the skin, and consists essentially 
of a felted interlacement of connective tissue and elastic fibres. In its deeper part, 
or stratum reticulare, the fibrous bundles are coarse and form an open network, in 
the meshes of which are vessels, nerves, pellets of fat, hair follicles, and glands. 
This reticular stratum passes, as a rule, without any line of demarcation, into the 
panniculus adiposus or subcutaneous fatty tissue, but in some parts it rests upon a 
layer of striped or uastriped muscular fibres—the latter in the case of the scrotum. 
In the superficial layer, or stratum papillare, of the corium, the connective tissue- 
bundles are finer and form a close network. Projecting from its free surface are 
numerous finger-like, single, or branched elevations, termed papille (Fig. 537), the 
free ends of which are received into corresponding depressions on the under surface 
of the epidermis. These papillee vary in size, being small on the eyelids, but large 
on the palms and soles, 
where they may attain 
( Simatemn length of 225 » and 
=— ( corneum produce the permanent 
curved ridges already 
= Stratum lucidum alluded to. Each ridge 
Betieam usually contains two 
rows of papillee, between 
Sieh which the ducts of the 
mucosumn sweat glands pass to 
St aaa reach the surface. The 
germinativuni papillee consist of fine 
Neccons connective tissue and 
Bee iC elastic fibres, mostly 
arranged parallel to the 
long axis of the papilla. 
The majority contain 
capillary loops, but some 
the terminations of 
nerves. The superficial 
surface of the corium is 
= Blood-vessels_ — Govered by a thin homo- 
a ee geneous basement mem- 
brane. 
- = ; The epidermis covers 
the corium; it 1s non- 
Fig. 5387.—VERTICAL SECTION On EPHD EMS AND PAPILLA OF CORIUM vascular and consists of 
(highly magnified). ar : : 
stratified epithelium. 
Its superficial layers are modified to form the stratum corneum or aorny layer of 
the skin, which may be separated by maceration or blistering from the deeper, 
softer portion, or stratum mucosum (Malpighi). The epidermis consists from within 
outwards of the following five strata (Fig. 537) :— 
|. The basilar layer or stratum germinativum, comprising a single stratum of 
al 
\ 
Vascular papilla cf corium 
