THE CERUMINOUS GLANDS 1297 



the eyelid. They are also rather scanty on the dorsal surface of the trunk 

 and neck, more numerous on the ventral surface of these parts and on the 

 extensor surfaces of the extremities, still more numerous on the flexor surfaces, 

 and most numerous on the volar surface of the hands and plantar surface of the 

 feet. They vary from less than 57 to more than 370 to the square centimetre. 

 The total number has been variously estimated at from two to fifteen millions. 

 Each gland (fig. 1057) consists of a secretory portion or body [corpus gl. 

 sudoriferse], and an excretory duct [ductus sudoriferus], which opens on the sur- 

 face of the skin by a mouth visible to the unaided eye, the so-called 'pore' [porus 

 sudoriferus]. Occasionally the duct opens into a hair follicle. 



The bodies of the glands are irregular or flattened spherical masses, yellowish or yellowish 

 red in colour and somewhat transparent. They vary in size from .06 to 4 mm. or more with a 

 mean diameter of .2 to .4 mm., the largest being found in the axilla. They are formed of the 

 irregularly, many times coiled, terminal part of the gland tube. The bodies of the glands are 

 situated in the deeper part of the corium or in the subcutaneous tela. 



The wall of the rather wide-lumened gland tube is formed of a single layer of cubical or col- 

 umnar epithelium containing fat and pigment granules and surrounded externally by a basement 

 membrane. Enclosing these is a more or less dense connective-tissue sheath. In many of the 

 glands, especially the larger ones, there is a layer of obliquely running unstriped muscle fibres, 

 the so-called myoepithelium, between the basement membrane and the cells. In some cases 

 the bodies of the glands are imbedded in a more or less dense mass of lymphoid tissue. 



The ducts, beginning as several coils bound up with those of the bodies, extend often in a 

 straight or slightly wavy course nearly at right angles to the surface as far as the epidermis. 

 This they pierce as spiral canals of from two to sixteen turns, more marked where the epidermis 

 is thickest (fig. 1041), and opened on the surface by somewhat widened funnel-shaped mouths. 

 The ducts pass between the papillse of the corium and open on the summits of the cutaneous 

 cristse where these are present. The diameter of the ducts is distinctly smaller than that of 

 the secreting part of the glands, and this is true of the lumen also. 



The ducts are lined by a stratified epithelium composed of two, three, or more layers of cells 

 resting on a basement membrane without any intervening layers of muscle-cells, and surroimded 

 by a connective-tissue sheath. This latter as well as the basement membrane ceases at the 

 epidermis and the epithelial cells of the duct walls join those of the stratum germinativum. The 

 duct for the rest of its course to the surface is merely a canal through the cells of the epidermis. 



The degree of development of the sweat glands varies with the situation, the individual, and 

 also racially, as instanced by their great development in the negro. In some individuals the 

 perspiration is much more profuse than in others. The glands are smaller in the aged than in 

 the young. The odour of the sweat is peculiar and more or less characteristic, varying with the 

 individual. 



The sudoriferous glands in the axillary region seem to be in some way connected with the sex- 

 ual function for although a large number persist as small glands, others undergo further develop- 

 ment beginning about the ninth year in the female and at puberty in the male. These glands in 

 places form almost a continuous layer and are formed of large partly branched tubules with high 

 secreting cells. The reddish colour of the sweat in the axillary and some other regions, especially 

 in certain individuals, is probably derived from the pigment granules which are found in the 

 glands here. The oil in the secretion lubricates the skm and keeps it soft and supple. 



Blood-supply of the sudoriferous glands. — The sudoriferous glands are supplied from the 

 deep cutaneous plexus by an abundant network of arteries which surround and penetrate 

 between the coils of the gland tubules. 



Nerves.— -There is an enclosing network of nerve fibres some of which have been traced to 

 the gland cells. 



Development. — The sudoriferous glands are seen first in the fourth or fifth foetal month. 

 The anlages resemble closely those of the hair, but the cells are not so loosely packed. They 

 project down as solid plugs which become long, slender, and tortuous rods. In the seventh 

 foetal month the rods begin to develop a lumen in the deeper parts, which also now begin to coil. 

 A lumen soon develops also in the superficial parts and joins that in the deeper part of the 

 gland. The outer of the two layers of epithelium in the ducts becomes transformed at its transi- 

 tion into the gland proper into the myoepitheUal layer. 



The ciliary glands [gl. ciliares; Molli] are modified sudoriferous glands of the 

 branched tubo-alveolar type. They have simpler coils but are larger than ordi- 

 nary sweat glands. They are situated in the eyelids near their free borders 

 and open into the follicles of the cilia or close to them (see Section VIII). 



The circumanal glands [gl. circumanales] are found in a circular area about 

 1.5 cm. wide which surrounds the anus, a short distance from it. 



These glands are several times the size of the ordinary sweat glands and resemble the glands 

 found in the axilla, their secretion likewise having a strong odour. They are branching tubular 

 glands. The other kinds of glands which are found in this same area are ordinary sweat glands, 

 glands with straight ducts, with saccules and secondary alveoli, and tubo-alveolar glands. 



Cerumimous glands [gl. ceruminosse] are glomiform glands somewhat modi- 

 fied from the sudoriferous type. They are branched tubo-alveolar glands 



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