132 PHYSIOLOGY. 



filled out by the liquids of the cell. Suppose, for the 

 inner layer, grapes set on end, and so closely packed 

 together as to press each other into elongated prisms. 

 Then layers less closely pressed, more nearly spherical; 

 then layers of cells with less liquid in them, and somewhat 

 shrunken, like raisins; then still dryer cells, flattened 

 parallel with the surface of the skin ; and last, in the outer 

 part, layers of cell walls, dry and empty, pressed flat like 

 empty grapeskins. The flat cell walls come off in flakes 

 (called dandruff from the scalp) from all the surface of 

 the skin, and new cells are continually formed in the 

 deeper layers. 



The Color of the Skin. The pigment, which gives 

 color to the skin, lies in the deeper layers of the epidermis. 

 In albinos this is wanting; in persons with a fair skin it 

 is small in amount, in dark skins more abundant. Where 

 the pigment is irregularly scattered it causes freckles, etc. 



A Blister. A blister is caused by separating the outer, 

 harder layer of the epidermis from the inner, softer, darker 

 layer of the epidermis, as shown at B in Fig. 49. Serum, 

 or blood, fills the space between the separated layers. 



The Dermis. The dermis consists chiefly of tough 

 interlacing fibers. Hence the strength and durability of 

 leather, which is the dermis preserved and prepared. . The 

 epidermis is usually removed in tanning. The dermis is 

 richly supplied with blood capillaries and lymph capillaries, 

 but the epidermis has neither. 



Papillae. The outer surface of the dermis has numer- 

 ous conical elevations. Over most of the skin there is no 

 evidence of these papillae, as the epidermis envelops them. 

 But on the palm and sole the papillae are in rows, and 

 these rows are indicated by the fine ridges. 



