The glands occurring in the skin are the sador ipurons or sweat glands, the Rcbaceous or fat glands, and the ceruuinors glands. The sweat glands exist in almost every part of the human skin. They lie in small pits in the deepest parts of the true skin, and sometimes entirely below the skin. Their orifices can be seen in the mid dle of the cross grooves that intersect the ridges of the papillae on the hands and feet, their ar rangement being here necessarily regular, while in other parts they are irregularly scattered. Their size and number in different regions of the skin correspond with the amount of perspiration yielded by each part; thus they are nowhere so much developed as in the axilla or armpit. In that part of the region which in the adult is more or less covered with hair, they form a layer of a reddish color, about an eighth of an inch thick. They are soft, and more o• less flattened by their pressure on one another, being imbedded in delicate connective tissue, and covered and permeated with a network of capillaries. On isolating one of these glands, and highly magni fying it, it is found to consist of a solitary tube, intricately raveled, one end of which is closed and hidden within the glandular mass, while the other emerges from the gland. The wall of the tube consists of an outer or basement membrane, with which the blood-vessels are in contact. and an epithelium, lining the interior, the former disappearing when the tube reaches the surface of the papilla. The duct, on leaving the gland, follows a meandering and rather spiral direction through the reticular portion of the eutis to the interval between the papillae, when it becomes straight; and it again assumes a spiral course in perforating the cuticle.
The glands are small whitish glands, which exist in almost every part of the skin. ex cept the palms and soles, and are especially abundant in the scalp, face (the nose being par ticularly rich in them), and about the anus. They are usually connected with the hairs, and consist of a duct terminating in a blind pouch like or pear-shaped extremity. The basement membrane of these glands is lined by an epithe limn, in the particles of which are included gran ules of fatty or sebaceous matter, which, having become detached, constitutes the secretion. These glands are the seat of the parasite known as Amens follieulorum The ecruminous glands are brown simple glands, in external appearance like the sudoripa rous glands, occurring in the cartilaginous por tion of the external meatus of the ear. They yield an adhesive hitter secretion, which protects the membrane of the tympanum from the access of dust, insects, etc.
Regarded as a protective covering, the skin possesses the combined advantages of toughness, resistance, flexibility, and elasticity; the connec tive framework being the part which mainly con fers these propertioi, although the epidermis co operates with it. The subcutaneous layer of fat, and the modifications of epidermis in various forms, as hairs, wool, feathers, scales, etc., serve for the preservation of warmth, and occasionally (when they occur as claws, talons, etc.) as means
of offense or defense. Besides preserving the warmth of the body, the skin has also the power of reducing body temperature by the evaporation of sweat. The skin is the seat of a twofold ex cretion, viz, of that fo•nmed by the sudoriparous glands and that formed by the sebaceous glands. The fluid secreted by the sudoriparous glands is usually formed so gradually that the watery por tions of it escape by evaporation as soon as it reaches the surface; but in certain conditions, as during strong exercise. or when the external heat is excessive, or in certain diseases, or when the evaporation is prevented by the application of a texture impermeable to air, as for example oiled silk, or mackintosh, or india-rubber cloth, the se cretion. instead of evaporating, collects on the skin in the form of drops of fluid. When it is stated that the sweat contains siren. lactates, ex tractive matters, etc., and that the amount of wa tery vapor exhaled from the skin is on an average two pounds daily, the importance of the sudo riparous glands as organs of excretion will he at once manifest. The secretion of the sebaceous glands is a semi-fluid oily mass, which often solidi fies into a white viscid tallow-like matter on the surface o• in the glandular duets, from which it can be removed by pressure, in a form resembling that of a small whitish worm or maggot.
The skin is, moreover, an organ of absorption. Mercurial preparations, when rubbed into the skin, have the same action as when given inter nally. Potassio-tartrate of antimony, when rubbed into the skin in the form of ointment or solution, may excite vomiting, or an eruption ex tending over the whole body, and many other illustrations might be given. The effect of rub bing is probably to force the particles of the mat ter into the orifices of the glands, where they are more easily absorbed than they would be through tlie epidermis. It has been proved by experiment that the skin has the power of absorbing water, although to a less extent than occurs in thin skinned animals, such as frogs and lizards. This fact has a practical application. In severo cases of dysphagia—dillicult swallowing—when not even fluids can be taken into the stomach, immersion in a bath of warm water, or of milk and water, may assuage the thirst. Sailors, also, when destitute of fresh water, find their urgent thirst allayed by soaking their clothes in salt water. Further, the skin possesses a respiratory function, giving off a small amount of carbon dioxide and taking up a small quantity of oxygen in twenty-four hours. In thin-skinned animals such as the frog, the excretion of carbon dioxide through this channel is very active. When a frog is innnersed in oil death takes place sooner than by ligature of the bronchi, but in the case of man and the higher animals, where varnish and other impervious substances have been applied to the skin, death has taken place from other causes than suffocation.