THE SKIN. 



573 



the prepuce of the clitoris. In the palms of the hands and the 

 soles of the feet there are no sebaceous glands. 



The relation of the glands to the hair varies greatly accord- 

 ing to the size of the latter. The largest sebaceous glands are 

 found in the naso-labial folds; here the fine lanugo hairs are 

 subordinate formations, piercing the duct at an acute angle. At 

 the extensor surfaces of the extremities and the posterior aspect 

 of the trunc the sebaceous glands are elongated j in the axillae 

 they are flattened. On the scalp they are sometimes small, 

 pear-shaped structures, and usually two of them empty into one 

 hair-pouch, both being under the control of the same fan-like 

 arrectorpili muscle (Hesse). (See Fig. 239.) Sometimes, however, 

 they attain a considerable size. In horizontal sections of the 



FIG. 240. SCALP OF MAN. HORIZONTAL SECTION. 



H, root of hair, surrounded by its sheaths ; 8, sebaceous gland ; F, follicle common to the 

 hair-roots and the sebaceous glands. Magnified 200 diameters. 



scalp we find groups composed of roots of hair and sebaceous 

 glands, inclosed by the fibrous connective tissue of the derma, 

 which sends delicate prolongations between the epithelial forma- 

 tions. The numerous acini visible in this situation do not 

 correspond to single sebaceous glands, but to their branching 

 lower ends. (See Fig. 240.) 



In specimens of sebaceous glands, preserved in a chromic 

 acid solution, the acini appear filled with fat, and the lining 



