ORGANS OF THE BODY. 



609 



Fig. 568. A sebaceous gland, a 

 the gland vesicles; b, excretory 

 duct; c, the follicle of a downy 

 hair ; d, shaft of the latter. 



304. 



The sebaceous glands (fig. 568), small structures included in the race- 

 mose class, are to be found likewise almost everywhere over the whole 

 surface of the skin, although less extensively 

 distributed than the sweat tubules. 



Their secretion is essentially a fatty one 

 (fig. 569) ; its mode of origin has been already 

 treated of at 196. 



The sebaceous glands, always seated. in 

 the corium itself, and never in the subcu- 

 taneous areolar tissue, are, as a rule, asso- 

 ciated with the presence of the large and 

 small hairs of the body, into whose follicles 

 they empty themselves, either singly, doubly, 

 or in greater number. While in relation 

 to the larger, hair follicles they appear but 

 as lateral appendages to the same with the 

 downy hairs, the case is altered, the hair fol- 

 licles of the latter seeming but appendages 

 of the glandular organs. In addition to these 

 sebaceous glands connected ^with hairs, the "hair-follicle glands," there 

 exist others found only on bald parts of 

 the body, which pour out their secretion 

 directly on the surface. The naked parts of 

 the skin are almost, without exception, des- 

 titute of them, such as the palm of the 

 hand, sole of the foot, and last joints of 

 both fingers and toes. On the whole these 

 are not widely distributed, and only occur 

 in certain parts of the sexual organs, namely, 

 on the prepuce and glans penis (known 

 there as the glands of Tyson), and on the 

 labia minora of the female. 



The structure of the sebaceous glands, 

 which range in diameter from 0'2 to 2'2 

 mm., is very different in different cases. 

 When small and simple their form is that 

 of a wide, shallow sac. Others, again, are 

 found at whose lower ends isolated buds 

 commence to present themselves, which be- 

 come more and more frequent, acquiring 

 eventually in some cases a flask-like form 

 (fig. 569, A), and in others a more globular 

 shape. These gland vesicles, whose length 

 is consequently very various, differ also con- 

 siderably in transverse measurement, ranging 

 from 0-0564 to 0*0751 mm., or even 0-2256 

 mm. The largest are observed on the nose, 

 scrotum, mons veneris, and labia majora. 

 The envelope of the vesicles and excretory 

 passage is not, as is the case with most 

 glands, a transparent structureless membrane, but consists of streaky con- 



Fig. 569. A, the vesicle or a seba- 

 ceous gland, a, the gland cells 

 next the wall; 6, cast-off elements 

 filling cavity of the vesicle, and con- 

 taining oily matters, , the same 

 cells more strongly magnified. </, 

 small elements belonging to the 

 walls, and poor in fat; 6, larger 

 richly filled; c, a cell with large 

 confluent globules ; d, another with 

 a single drop of oil. 



