74 PRACTICAL MICROSCOPY. 



brane. The latter constitutes the entire wall of the duct as the sur- 

 face of the epidermis is approached, the cellular elements having dis- 

 appeared. 



Krause estimated the number of sweat glands at over two millions. 



SEBACEOUS GLANDS. 



These glands are -little sacs or lobules, one or more of which open 

 into each hair follicle. These sacs are entirely filled with polyhedral 

 cells (vide Fig. 58). At the neck of the gland the cells become 

 granular, fatty, and disintegrated, producing the sebum. 



MUSCLES OF THE HAIE FOLLICLES. 



Attached to the fibrous layer of each hair follicle is a small band 

 of involuntary or smootli muscular fibre the arrector pili. This 

 passes obliquely toward the surface of the skin; and when contrac- 

 tion takes place, the follicle and hair are elevated, producing the 

 phenomenon known as goose-flesh. 



PKACTICAL DEMONSTRATION. 



Remove the skin from the parts below as soon after death as prac- 

 ticable. Tissue may frequently be secured after surgical operations 

 from stumps, etc. Dissect deeply so as to preserve the subcutaneous 

 tissue. Small cubes from the finger-tips, the palm of the hand, the 

 scalp, and the groin may be hardened quickly in strong alcohol ; and 

 vertical sections should be made as soon as the tissue has become suf- 

 ficiently firm. Stain with ha3ma. and eosin, and mount in dammar. 



The structure of hairs may be best demonstrated by washing the 

 soap from lather, after shaving, with several changes of water. 

 When clean, decant the water and add alcohol. After twenty-four 

 hours again decant and add oil of cloves. With a, pipette carry a 

 drop of the oil with the deposited hair cuttings to a slide, remove as 

 much of the oil as possible with slips of blotting-paper, and mount 

 in dammar. Oblique, vertical, and transverse sections may be readily 

 obtained by this method. 



VERTICAL SECTION OF SKIN FROM THE GROIN. 



(Vide Fig. 59.) 

 OBSERVE : 



(L.)* 



1. The horny layer of the epidermis. (The stratum lucidum 

 will hardly be demonstrable on account of the thinness of the epider- 

 mis in this region.) 



* Low power, i. e., from thirty to sixty diameters. 



