NORMAL HISTOLOGY AND ORGANOGRAPHY. 



glands that vary in size from 0.2 to 0.5 mm. The 

 excretory duct is short and wide and opens into the 

 upper third of the follicle. This duct is lined by 

 stratified epithelium that is directly continuous with 



the outer root 

 sheath of the hair 

 follicle. The cells of 

 the alveoli are very 

 large and contain fat 

 globules that vary 

 in size and give a 

 reticular appearance 

 to the cytoplasm. 

 The nuclei are rela- 



rig. 252. section of two alveoli of a 



sebaceous gland. tively small. The 



cells completely fill 



the alveoli so that the latter appears to be solid. 

 The cells disintegrate and change directly into secre- 

 tion, which is then poured into the follicle as sebum. 

 The renewal of lost cells takes place by constant 

 proliferation of basal cells. 



It is quite common in the scalp to find sebaceous 

 cysts, or wens, which result from an occlusion of the 

 duct and an enlargement of the gland. These cysts 

 are lined by a simple layer of epithelium and filled 

 with a white, waxy, or semisolid fluid quite analo- 

 gous to the sebum. Wens are of slow growth and 

 cause no disturbance, unless they get very large or 

 become infected by being carelessly opened. The 

 radical cure consists in their complete removal, in- 

 cluding the epithelial wall. 



