392 



EXCRETIOK 



The glandular coils vary in size from T | T to ^ of an inch ; the smallest coils being 

 found beneath the skin of the penis, the scrotum, the eyelids, the nose, and the convex 

 surface of the concha of the ear, and the largest, on the areola of the nipple and the peri- 

 neum. Very large glands are found mixed with smaller ones in the axilla, but these 

 produce a peculiar secretion which will be specially considered. The coiled portion of 

 the tube is about T | 7 of an inch in diameter and forms from six to twelve convolutions. 

 It consists of a sharply-defined, strong, external membrane, from -^ -^ ~ - to 7 Vo f an mcn 

 in thickness, very transparent, uniformly granular, and sometimes indistinctly striated. 

 This is of uniform diameter throughout the coil and terminates in a very slightly dilated, 

 rounded, blind extremity. It is filled with epithelium in the form of finely granular mat- 

 ter, usually not segmented into cells, and provided with small, oval nuclei. The glandu- 

 lar mass is surrounded by a plexus of capillary blood-vessels, which send a few small 

 branches between the convolutions of the coil. Sometimes the coil is enclosed in a deli- 

 cate fibrous envelope. 



The excretory duct is simply a continuation of the glandular coil. Its course through 

 the layers of the true skin is nearly straight. It then passes into the epidermis between 

 the papilla of the corium, and presents, in this layer, a number of spiral turns. The 

 spirals vary in number according to the thickness of the epidermis. Sappey has 

 found from six to ten in the palms of the hands and from twelve to fifteen in the soles 

 of the feet. As it emerges from the glandular coil, the excretory duct is somewhat nar- 

 rower than the tube in the secreting portion ; but, as it passes through the epidermis, it 



again becomes larger. It possesses the same external 

 membrane as the glandular coil and is lined generally 

 by two layers of cells of pavement-epithelium. 



In a section of the skin and the subcutaneous tissue, 

 involving several of the sudoriparous glands with their 

 ducts, it is seen that the glandular coils are generally 

 situated at different planes beneath the skin, as is indi- 

 cated in Fig. 112. 



Robin has described a variety of sudoriparous glands 

 in the axilla, which do not differ so much from the 

 glands in other parts in their anatomy as in the charac- 

 ter of their secretion. The coil in these glands is much 

 larger than in other parts, measuring from ^V to TF f 

 an inch ; the walls of the tube are thicker, and they 

 present an investment of fibrous tissue with an internal 

 layer of longitudinal, unstriped muscular fibres; and, 

 finally, the tubes of the coil itself are lined with cells 

 of pavement-epithelium. They are very numerous in 

 the axilla, forming a continuous layer beneath the skin, 

 ^lixed with these, are a few glands of the ordinary va- 

 riety. 



Estimates have been made by different writers of 

 the absolute number of sudoriparous glands in the body 

 and the probable extent of the exhalant surface of the 

 skin. One of the most careful, and probably the most 

 reliable of these estimates, is that made by Krause; 

 but, like all estimates of this kind, the results are to 

 be taken as merely approximative. Krause found 

 great differences in the number of perspiratory open- 

 ings in different portions of the skin, and he estimated the number in a square inch in 

 certain parts, as follows : On the forehead, he found 1,258 glands to a square inch ; on 

 the cheeks, 548; on the anterior and lateral portions of the neck, 1,303; on the breast 



FIG. 112. Siidori 'parmtK glands; mag- 

 nified 20 diameters. (Sappey.) 



1. 1, epidermis ; 2. 2. mucous layer ; 3. 3, 

 papillae; 4,4, derma; 5. 5. subcutane- 

 ous areolar tissue; 6, 6, 6, 6, sudoripa- 

 rous erlands ; 7. 7. adipose vesicles ; 8, 8, 

 excretory ducts in the derma; 9, 9, ex- 

 cretory ducts divided. 



