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Henry Gray (1825–1861).  Anatomy of the Human Body.  1918.
 
the glands are of large size, distinctly lobulated, and often become much enlarged from the accumulation of pent-up secretion. The tarsal glands of the eyelids are elongated sebaceous glands with numerous lateral diverticula.


FIG. 946– Body of a sudoriferous-gland cut in various deirections. a. Longitudinal section of the proximal part of the coiled tube. b. Transverse section of the same. c. Longitudinal section of the distal part of the coiled tube. d. Transverse section of the same. (Klein and Noble Smith.) (See enlarged image)

  The Sudoriferous or Sweat Glands (glandulæ sudoriferæ) are found in almost every part of the skin, and are situated in small pits on the under surface of the corium, or, more frequently, in the subcutaneous areolar tissue, surrounded by a quantity of adipose tissue. Each consists of a single tube, the deep part of which is rolled into an oval or spherical ball, named the body of the gland, while the superficial part, or duct, traverses the corium and cuticle and opens on the surface of the skin by a funnel-shaped aperture. In the superficial layers of the corium the duct is straight, but in the deeper layers it is convoluted or even twisted; where the epidermis is thick, as in the palms of the hands and soles of the feet, the part of the duct which passes through it is spirally coiled. The size of the glands varies. They are especially large in those regions where the amount of perspiration is great, as in the axillæ, where they form a thin, mammillated layer of a reddish color, which corresponds exactly to the situation of the hair in this region; they are large also in the groin. Their number varies. They are very plentiful on the palms of the hands, and on the soles of the feet, where the orifices of the ducts are exceedingly regular, and open on the curved ridges; they are least numerous in the neck and back. On the palm there are about 370 per square centimeter; on the back of the hand about 200; forehead 175, breast, abdomen and forearm 155, and on the leg and back from 60 to 80 per square centimeter. Krause estimates the total number at about 2,000,000. The average number of sweat glands per square centimeter of skin area in various races as shown by the fingers is as follows: 1
American (white)
558.2
American (negro)
597.2
Filipino
653.6
Moro
684.4
Negrito (adult)
709.2
Hindu
738.2
Negrito (youth)
950.0
  They are absent in the deeper portion of the external auditory meatus, the prepuce and the glans penis. The tube, both in the body of the gland and in the duct consists of two layers—an outer, of fine areolar tissue, and an inner of epithelium (Fig. 946). The outer layer is thin and is continuous with the superficial stratum of the corium. In body of the gland the epithelium consists of a single layer of cubical cells, between the deep ends of which and the basement membrane is a layer of longitudinally or obliquely arranged non-striped muscular fibers. The ducts are destitute of muscular fibers and are composed of a basement membrane lined by two or three layers of polyhedral cells; the lumen of the duct is coated by a thin cuticle. When the cuticle is carefully removed from the surface of the corium, the ducts may be drawn out in the form of short, thread-like processes on its under surface. The ceruminous glands of the external acoustic meatus and the ciliary glands at the margins of the eyelids are modified sudoriferous glands.
Note 1.  Journal of Anatomy and Physiology, vol. xliv. [back]

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