152 STRUCTURE OF THE SKIN. 



often loosens or breaks off a piece of the epidermis, but seldom 

 removes the derm is. The epidermis is thick over the palma 

 of the hands and soles of the feet ; elsewhere it is thin. 

 Not often seeing the whole thickness of the skin, we do not 

 easily get an idea of its real thickness. The skin constitutes 

 about one-fifteenth of the body's weight, and if tanned, makes 

 a moderately firm and thick leather very much resembling the 

 pigskin used for covering footballs, striking-bags, etc. 



The epidermis consists of many layers of cells packed 

 closety together. The deepest cells may be compared to 

 grapes with their cell walls plumply 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, while the old, dry, dead cells are continually thrown 

 off from the outer surface. 



The Pigment, or coloring matter, which gives color to the 

 skin, lies in the deeper layers of the epidermis. In albinos 

 this is wanting ; in persons having 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 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. 50. Serum, or blood, fills 

 the space between the separated layers. 



The dermis consists chiefly of tough fibers, interlacing in 



