264 APPLIED PHYSIOLOGY 



4. At the backs of the ends of the fingers and toes the 



epithelium is thickened and hardened to form the 

 nails. 



5. Digestive disturbances are the principal causes of a 



poor complexion. 



6. Paints and powders irritate the skin and have the 



same effect as dirt. 



7. Daily brushing the hair and frequently washing it 



with soap and water are the best means of keep- 

 ing it soft and glossy. 



8. Nails should be smoothly trimmed, and gently cleaned. 



9. The skin should be washed often enough to prevent 



an odor of perspiration. 

 10. The heat of hot baths dilates the arteries of the skin 



so that blood leaves the internal organs and brain 



and produces a feeling of rest and drowsiness. 

 n. f A cold bath contracts the arteries of the skin. But 



they soon dilate and produce a feeling of warmth 



and exhilaration, called the reaction. 

 12. If a cold bath is continued, the arteries again contract, 



producing chilliness and a feeling of exhaustion. 



DEMONSTRATIONS 



112. Examine a specimen of skin with a microscope. Notice the 

 network of connective tissue in the derma, and the numerous arteries 

 and veins. Notice its projections of papillae and their covering of 

 epithelium. Notice that the epithelial cells in the deepest layers are 

 large and round, and the outermost layers are flat and shriveled and can 

 scarcely be recognized. Notice a faint line of colored granules in the 

 third or fourth layer of cells. In a negro the colored layer is very dis- 

 tinct. The specimen will also probably show one or two winding sweat 

 glands. 



113. The skin specimen will probably show a few hairs, but one 

 specially prepared will be better. Notice the deep tubelike depression 



