216 



SPECIAL HISTOLOGY. 



Fig. 87. 



to him, the same is the case in the praeputial sac of the Weasel, whilst 

 in the Rat and Mouse, the prepuce contains true sebaceous glands of a 

 complicated structure. 



74. The minute structure of the sebaceous glands may be described 

 as follows : Each gland possesses an external delicate coat of connective 

 tissue, continued from the hair-sac, or, in the case of free glands, from 

 the corium, and containing masses of cells, which exhibit different con- 

 ditions, according to the part of the gland. If we proceed from the 

 excretory duct of one of them (Fig. 88 B\ we see, that not only the 

 fibrous coat of the hair-sac, but a portion of its inner root-sheath, also, 

 passes into the duct, and lines it with nucleated, rounded, or polygonal 

 cells, disposed in several (two to six) layers. This cellular layer is con- 

 tinued, becoming more and more delicate, into the remoter parts of the 



gland, and ultimately pene- 

 trates into the proper glan- 

 dular vesicles, clothing them 

 with a single, rarely a double, 

 layer. Internally to these 

 f cells, which are distinguished 

 by a greater or smaller 

 number of fat granules from 

 the epithelial cells above 

 them, there immediately suc- 

 ceed, in the glandular vesicles 

 themselves, others (Fig. 87 B b) containing more fat ; and these finally pass 

 into the innermost cells of the glandular vesicles, which are invariably 

 larger (of 0-016-0-028 of a line) than the middle and outermost cells, 

 are rounded or elongated in their form, and so filled with colorless fat 

 that they might, not improperly, be termed sebaceous cells (Fig. 87 B). 

 The fat contained in them appears either still to retain the form of dis- 

 crete drops (bb)j as in the outer cells, or, as is indeed more frequently 

 the case, under that of larger drops ; and in many cells there are but a 

 few of them, or even only a single one, which quite fills the cell (c?); in 

 consequence of which these cells greatly resemble the fat-cells of the 

 panniculus adiposus. If these innermost cells, which rarely exhibit 

 any nucleus, are traced onward towards the excretory duct, nothing is 



FiG. 87. Jl, a glandular vesicle of a common sebaceous gland; magnified 250 diameters: 

 a, epithelium sharply defined, but without any investing menibrana propria, and passing 

 continuously into the fat-cells, b (their contours are too indistinctly drawn), in the interior of 

 the glandular tube. B, sebaceous cells from the glandular tube, and the cutaneous sebaceous 

 matter; magnified 350 diameters: a, smaller nucleated cells, still more of an epithelial 

 character, and containing but little fat; b, cells abounding in fat, without visible nucleus ; 

 c, cell in which the fat is beginning to flow into one mass; d, cell with one fat-drop ; e,/, 

 cells from which the fat has partially escaped. 



