THE HAIR 



289 



triangular space beneath the corium, which is bounded by the arrector 

 pili muscle and the hair follicle. The saccules are lined by several 

 layers of polygonal epithelial cells the outermost of which are cuboidal 

 and rest upon the basement membrane. 



In the peripheral layers the lining epithelial cells multiply so actively 

 that the daughter-cells are pushed inward until they fill the entire sac- 

 cule. During this excursion they are progressively farther and farther 



removed from their source of 

 nutrition, and as they approach 

 the outlet or duct of the sac- 

 cule, a process of fatty degen- 

 eration appears within the cell, 



f 



., 



FIG. 277. SECTION OF A SEBACEOUS GLAND 

 FROM THE HUMAN SCALP, THROUGH POINT 

 OF OPENING INTO A HAIR FOLLICLE 

 (OBLIQUELY CUT). 



Between the basement membrane of the 

 sebaceous alveolus and the hair follicle, the 

 cells exhibit successively later stages of fatty 

 degeneration ending in the formation of 

 sebum. X 160. 



FIG. 278. CELLS FROM THE 

 CENTRAL PORTION OF THE 

 PRECEDING FIGURE, SHOW- 

 ING Two SUCCESSIVE STAGES 

 IN SEBUM FORMATION BY 

 PROCESSES OF FATTY META- 

 MORPHOSES OF THE CYTO- 

 PLASM. 



Note the shrunken character 

 of the nuclei of the upper more 

 degenerate cells. The cyto- 

 plasm is filled with fat spher- 

 ules. X 550. 



by which its protoplasm becomes changed into a granulofatty mass. 

 The accumulated product of this degeneration and final disintegration 

 of the epithelial cells forms the secretion of the gland. Continued cell 

 multiplication at the periphery maintains the integrity of the organ. 

 19 



