OF THE GLANDS OF THE SKIN. 217 



more easy to observe than that similar cells, applied uninterruptedly one 

 to the other, are continued into this also, i. e. into the canal lined by its 

 epithelium ; then, entering the hair-sac, they occupy the space between 

 the hair and the epidermis of the hair-sac, and are finally extruded. 

 These cells are the sole sources of the cutaneous sebaceous matter, a 

 substance which, when fresh and at the common temperature, is semi- 

 fluid, but in the dead subject more consistent, like butter or soft cheese, 

 whitish or whitish-yellow in color, sometimes viscid, at others friable. 

 Its cells, in the fresh secretion, adhere together more or less closely, 

 and are thence generally flattened and irregular in form ; their mem- 

 brane is not recognizable, and their contents are quite homogeneous, 

 and transparent, with a yellowish hue. If dilute alkalies, however, be 

 added, they swell up after a short time into beautiful round or elongated 

 vesicles, in which, in consequence of the penetration of the reagent, the 

 fat divides into separate drops of various sizes, and into irregular 

 masses ; at the same time the sebaceous matter becomes white, owing 

 to the numerous minute fatty particles which are produced, and larger 

 fat-drops are formed, probably in consequence of the solution of many 

 cells. Besides that in the cells, the sebaceous matter also contains free 

 fat, in larger or smaller quantity, and in some cases, perhaps, an exces- 

 sively minute amount of a clear fluid. 



It appears, then, that the cutaneous sebaceous matter is a secretion, 

 consisting, so to speak, only of formed elements, either cells containing 

 fat alone, or cells together with drops of fat. These constituents are 

 formed in the vesicular ends of the glands, in consequence of a produc- 

 tion of cells, which, as in the epidermic tissues in general, proceeds en- 

 tirely from the pre-existing cells, unaided by free cell-development, of 

 which there is in this case no indication. By endogenous development 

 round portions of contents, or by division, cells are continually produced 

 at the bottom of the glandular vesicles. These are at first pale, and 

 contain but few granules, like the epithelial cells from which they arise ; 

 but as they are forced towards the interior by cells developed after them, 

 they are very soon completely filled with moderately large, round, dark, 

 fat-granules. They thus proceed towards the excretory ducts ; and the 

 fat drops contained in them running more and more together, and the 

 membranes themselves becoming rather more resistant, they eventually 

 assume the form of the sebaceous cells above described. The free fatty 

 matter in the sebaceous secretion is formed, in certain cases, by the 

 solution of the cells whilst still in the interior of the glandular vesicles, 

 for, in fact, in many glands, free fat, in smaller or larger, often very 

 considerable drops (Fig. 86 B\ is met with, even in the terminal 

 vesicles ; however, it is also, perhaps, produced in consequence of its 

 draining from closed cells, a supposition which is not a little strengthened 

 by the circumstance, that the fat-containing cells in the excreted seba- 



