ELEMENTS OF PHYSIOLOGY 



or cutis. The dermis is called also the true skin. The 

 epidermis is composed of a mass of cells held together 

 by a cement something like the white of an egg. Those 

 near the surface (Fig. 2) are hard and flattened; 

 those deeper down, near the dermis, are round and 

 soft. The lowest layers contain a pigment con- 

 sisting of minute grains of coloring matter. The 



varying amount of this 

 pigment present causes 



Epider- i ' 



mis or the difference in hue of 

 Cutide the blonde and brunette 



Sweat 

 Glands 



Dermis ^^^ 

 or 



races. Freckles are due 

 to an increase of pig- 

 ment in patches of 

 neighboring cells. Some 

 persons lack the pig- 

 ment entirely; their hair 

 and skin are white, the 

 eyes pink. They are 

 called albinos. Albinos 

 are found among vari- 

 ous species of animals. 

 Among the specimens 

 in the British Museum 

 there are albino (or pure 

 white) blackbirds, tur- 

 keys, etc. 



3. The main part of the skin is the dermis, or cutis 

 (Fig. i); it is chiefly a network of fibers. This is the part 

 of the skin of animals that is tanned for leather. Did 

 you ever notice the fibrous appearance in the leather of a 

 shoe that has become much worn? Which side of leather 

 is smooth, the side covered by epidermis, or the other side ? 

 The human skin when tanned is said to make a leather 



Nutrient A rtery 

 FIG. i. Sectional View of the Skin, magnified. 



Find: oil (sebaceous) gland, sweat gland, sweat duct, 

 hair bulb. Compare thickness of epidermis, dermis, 

 and subcutaneous tissue. (Thornton.) 



