218 SPECIAL HISTOLOGY. 



ceous matter are seldom filled to distension, but appear for the most part 

 variously flattened, or even corrugated, and contain only a small quantity 

 of fat. Understood in this way, the formation of the cutaneous sebaceous 

 matter resembles in many respects that of the cuticle. The young, easily 

 soluble cells at the bottom of the glandular follicles may be compared 

 to the Malpighian cells of the ejiidermis, and the less soluble ones of 

 the secretion filled with fat, to the horny plates, which seems the more 

 appropriate, if we consider, 1, that the deep layer of the ejyidermis of 

 the hair-sac is continued into the ducts of the glands, and even the 

 outermost cells of the terminal vesicles; and 2, that the epidermis, in 

 some situations being constantly detached, form secretions (I refer to the 

 smegma prceputii of the penis and clitoris), substances which are, more- 

 over, to all appearance chemically allied to the sebaceous secretion ; for 

 the latter, it may be remarked, according to an analysis of the contents 

 of a distended gland by Esenbeck (Gmelin's " Handbuch der Chemie," 

 Bd. ii.), contains principally, fat, 24*2 ; albumen and casein, 24*2 ; ex- 

 tractive matters, 24 ; and phosphate of lime, 20 per cent. ; substances 

 which are found, at all events in part, in the smegma. 



Of nerves, I have seen no indication in the sebaceous glands, nor of 

 vessels distributed upon and between their lobules ; whilst numerous 

 minute vessels and even capillaries, undoubtedly exist around the larger 

 glands, most distinctly in the penis and scrotum, as well as in the 

 ear. I would, moreover, refer to the smooth muscles described above, 

 when speaking of the cutis, which are found in the neighborhood of the 

 sebaceous glands, and whose contraction is, perhaps, not inoperative 

 towards the emptying of their contents. 



§ 75. Development of the Sebaceous Grlands. — The first formation of 

 the sebaceous glands takes place at the end of the fourth and in the 

 fifth month, and is intimately connected with that of the hair-sacs, since 

 they make their appearance simultaneously with the hairs, or shortly 

 after, as outgrowths of the hair-sacs ; whence they are not all formed 

 at once, but those of the eyebrows, forehead, &c., first, those of the ex- 

 tremities last. The mode of their development, more precisely described, 

 is as follows : AVhen the rudiments of the hair-sacs have attained a 

 considerable development, and the first indication of the hair is visible 

 in them (Fig. 75, A, B), there are perceptible, on their outer surface, 

 small, indistinctly-bounded papillary processes {u, v), which consist of a 

 cellular substance, solid throughout and continuous with the outer root- 

 sheath, and of a delicate investment, which is continuous with that of the 

 hair-sac. These processes of the external root-sheaths of the hair-sacs, 

 as they may properly be called, at first of 0-02-0 -03 of a line in length, 

 and 0-01-0'016 of a line in thickness, now begin to grow in proportion 

 to the hair-sacs, become globular, and finally, while they extend them- 



