THE SKIS. 199 



The sebaceous glands can best be described in connection with 

 the hairs and their follicles. 



The bulbous attachment, or " root," of the hair, and the adjacent 

 portion of its shaft, are contained in an invagination of the corium 

 and epidermis, called the "hair-follicle" (Fig. 173,/). This is sur- 

 rounded by fibrous tissue, forming its external coat, which may be 

 imperfectly distinguished into an outer layer, containing relatively 

 abundant longitudinal fibres, and an inner layer, in which encircling 



FIG. 176. 

 ,a 



Section through the coiled end of a sweat-gland. (Klein.) a, &, duct in longitudinal and 

 cross-section ; c, d, sections of the secretory portion of the tubule. Above d is a little adi- 

 pose tissue. The rest of the section is composed of vascularized areolar tissue. 



fibres predominate. At the bottom of the follicle this fibrous tissue 

 becomes continuous with that of a vascularized papilla, similar to 

 those existing on the surface of the corium, which projects into the 

 root of the hair. 



The fibrous sac constituting the outer part of the hair-follicle is 

 lined with a continuation of the epidermis, leaving a cylindrical 

 cavity occupied by the hair. This layer of epithelium is reflected 

 upon the surface of the papilla, where it forms the root of the hair, 

 and then passes into the shaft, which is made up of cells, derived 

 from those of the root, that have suffered keratoid degeneration. 



The epithelium lining the follicle, as well as that which composes 

 the hair, is not of uniform character throughout, and has been divided 

 into a number of layers, to which different observers have given 

 special names. The group of cells surrounding the papilla are the 

 seat of the multiplication which results in the growth of the hair. 

 Upon the surface of the shaft these cells become transformed into 



