xii THE SKIN AND THE KIDNEYS 151 



epithelial cells in the under surface are nourished by 

 lymph that comes from the capillaries of the dermis, 

 while the flattened, dead, horny, or scaly cells of the 

 outer surface need no nourishment. These cells are 

 continually dropping off. In the deeper parts of the epi- 

 dermis we find very tiny particles of coloring matter 

 known as the pigment. In different persons and races 

 the pigment varies in color from a pale pink to a dark 

 brown or black ; and in amount, from none at all in 

 albinos and a little in white persons, to a great abun- 

 dance in deep-black negroes. Sometimes the pigment 

 is not evenly distributed, but occurs in patches called 

 freckles. The complexion depends upon the kind and 

 amount of pigment in the scarfskin. 



The dermis is well supplied with blood vessels and 

 nerves. The epidermis dips down into the true skin 

 between little projections called papillce. In these pa- 

 pillae of the dermis are located the nerve endings which 

 enable us to have sensations of touch, pain, and tem- 

 perature. 



115. Glands of the Skin. In the skin are found two 

 kinds of glands secreting very different fluids. They 

 are the oil or sebaceous glands, and the siveat glands. 



The sweat glands are long, convoluted tubes extend- 

 ing down into the true skin and opening by small pores 

 on the surface of the epidermis. These glands occur in 

 the skin everywhere but are most numerous in the palms of 

 the hands and the soles of the feet. It has been estimated 

 that in man there are between two and three millions of 

 sweat glands. These glands are constantly active, se- 



