284 SECRETION 



general surface, they produce essentially the same secretion, and their 

 anatomical differences consist simply in a multiplication of follicles (see 

 Plate VII, Fig. 7). 



The differences in the size of the sebaceous glands bear a certain 

 relation to the size of the hairs with which they are connected ; and as 

 a rule, the largest glands are connected with the small downy hairs. 

 These distinctions in size are so marked, that the glands may be divided 

 into two classes ; those connected with the long hairs of the head, face, 

 chest, axilla, genital organs and with the coarse short hairs, and those 

 connected with the fine downy hairs. 



The glands connected with the larger hair-follicles are of the simple 

 racemose variety and are T | T to -$ of an inch (0.21 to 0.64 millimeter) 

 in diameter. Two to five of these glands usually are found arranged 

 around each hair-follicle. They discharge their secretion at about the 

 junction of the upper third with the lower two-thirds of the hair-follicle. 

 The follicles of the long hairs of the scalp usually are provided each with 

 a pair of sebaceous glands, measuring T ^ to y 1 ^ of an inch (0.21 to 0.34 

 millimeter) in diameter. Encircling the hairs of the beard, the chest, 

 axilla and genital organs, are large glands, some of them -fa of an inch 

 (0.64 millimeter) in diameter, arranged in groups of four to eight. 



The glands connected with the follicles of the small downy hairs are 

 so large as compared with the hair-follicles that the latter seem rather 

 as appendages to the glandular structures. These glands are of the 

 compound racemose variety and present sometimes as many as fifteen 

 culs-de-sac. The largest are found on the nose, the ear, the caruncula 

 lachrymalis, the penis and the areola of the nipple, where they measure 

 A to iV f an mcn (-5 l to 2 - r millimeters). The glands connected 

 with the downy hairs of other parts usually are smaller. The glands 

 of Tyson, situated on the corona and cervix of the glans penis, are 

 sebaceous glands of the compound racemose variety. 



The follicles composing the simple glands and the follicular termina- 

 tions of the simple and compound racemose glands are formed of a 

 delicate structureless or slightly granular membrane, with an external 

 layer of inelastic and small elastic fibres and are lined with cells. Next 

 the membrane, the cells are polyhedric, pale and granular, most of them 

 presenting a nucleus and a nucleolus ; but the follicle itself contains 

 fatty granules and the other constituents of the sebaceous matter, with 

 cells filled with fatty particles. These cells abound in the sebaceous 

 matter as it is discharged from the duct. The great quantity of fatty 

 granules and globules found in the ducts and follicles of the sebaceous 

 glands renders them dark and opaque when examined with the micro- 

 scope by transmitted light, except when studied in very thin sections, 



