I38 SEBACEOUS GLANDS. [SECT. 75. 



the excretory canals lined with epithelium — then enter the hair- 

 follicle, where they occupy the space between the hair and epi- 

 dermis of the hair-follicle, and are, finally, discharged externally. 

 These cells alone form the sebaceous matter of the skin. This is, 

 at the temperature of the living body, a semi-fluid substance, but 

 in the dead subject, has more of a cheesy consistence; by the 

 addition of dilute alkalies, it can be easily shown to consist of cells. 

 Besides the sebaceous cells, the sebaceous matter of the skin also 

 contains free fat. 



According to the above remarks, the sebaceous matter of the 

 skin is a secretion, which may be said to consist solely of distinct 

 particles, namely, cells containing fat, or such cells intermixed 

 with fat-drops. These cells are developed in the vesicular extre- 

 mities of the glands by a process of cell-formation, depending 

 entirely, as in epidermic structures generally, on pre-existing cells, 

 and without free cell-formation, of which in this case there is not 

 the slightest evidence. The free fat in the sebaceous matter of the 

 skin arises from the bursting of the sebaceous cells, and perhaps, 

 also, by transudation through the cell-wall. So considered, the for- 

 mation of the sebaceous matter of the skin resembles, in many re- 

 spects, the production of the epidermis. The young and readily 

 soluble cells at the bottom of the glandular vesicles may be com- 

 pared to the Malpighian cells of the epidermis, and the less soluble 

 ones, filled with fat, to the horny plates. This comparison will ap- 

 pear the more apt, when it is remembered, i.that the deep layer of 

 the epidermis of the hair-follicle is continued uninterruptedly into 

 the gland-ducts and the outermost cells of the terminal vesicles ; and 

 2. that the epidermis also forms in some places a secretion, by con- 

 tinual detachment of its cells (I refer to the smegma prceputii 

 penis et clitoridis), and also yields substances which, to all appear- 

 ance, are chemically allied to sebaceous matter. 



I have not observed nerves on the sebaceous glands ; but fine 

 vessels, and even capillaries, are found around the larger glands, 

 especially those of the penis and scrotum, and ear. I may again 

 refer to the smooth muscles, described when speaking of the 

 corium as situate in the neighbourhood of the sebaceous glands, 

 whose contraction can scarcely be unconcerned in the evacuation 

 of the secretion. 



§ 75. Development.— The formation of the sebaceous glands 

 takes place at the end of the fourth and in the fifth month, and 

 is most intimately connected with the development of the hair- 



