154 THE SKIN. 



submucous layer of mucous membranes. This tissue contains 

 the larger vascular and nervous branches, and Pacinian cor- 

 puscles ; the hair-follicles and sweat-glands project down into 

 it. Next to the corium the subcutaneous tissue is mostly 

 loose and areolar, while deeper is a variable and often thick 

 layer of fatty tissue, the pannieulus adiposus. 



The sudoriparous or sweat-glands (Fig. 63) occur in great 

 abundance over the entire skin, and are derived from down- 

 growths of the epidermic epithelium. They are simple tubu- 

 lar glands of the serous type, consisting of single tubes lined 

 by epithelium resting on a basement-membrane, and sup- 

 ported in the surrounding connective tissue. They extend 

 from the surface downward into the subcutaneous tissue or 

 lowest part of the corium, and their deeper portions are much 

 convoluted. They consist of two parts, a secreting portion 

 and an outlet-duct. The secreting portion consists of the 

 lower part of the tube, sometimes somewhat branched, and is 

 coiled and convoluted into a rounded nodule situated in the 

 subcutaneous tissue. Its calibre is larger than that of the 

 outlet portion, and it is lined with a layer of columnar 

 epithelium. Between the epithelium-cells and their basement- 

 membrane occur scattered involuntary muscle-cells. 



The outlet-duet is a narrow tube of uniform size lined with 

 two layers of spheroidal epithelium-cells. After leaving the 

 convoluted secretory portion of the tube it pursues a straight 

 or slightly wavy course to the epidermis, which it enters be- 

 tween the papillae. In the stratum Malpighii its lining is 

 formed by the cells of that layer. Through the stratum 

 corneum the duct passes to the surface in a spiral or cork- 

 screw course through the horny substance. The ceruminous 

 glands of the ear are modified sweat-glands. 



The hairs occur in the skin over nearly the entire surface, 

 being especially numerous and well developed in certain 

 regions. They are composed of horny cells derived from the 

 epidermis. The lower end of each hair exhibits a rounded 

 enlargement, the bulb. 



The root of the hairs, the portion imbedded in the skin, 

 extends into the subcutaneous tissue, and is supported in and 

 grows from a sheath, the hair-follicle, formed by a downgrowth 

 of the epidermis and corium. 



