THE SKIN 17 



it with a woolen cloth. Note change in reading. After it regains first 

 reading, repeat, covering it with a cotton cloth of same weight and tex- 

 ture ? Conclusion ? Expose wrists or arms to sun for five minutes, one 

 protected by the cotton, the other by the wool. Result ? Conclusion? 



Experiment 10. Rates of Heat Absorption and Radiation by Different 

 Colors. — Expose thermometer to sunlight, covered successively by pieces 

 of cloth of same thickness, material, and texture. Use black, blue, red, 

 yellow, and white cloth. Note rise of temperature for equal times in each 

 case; also the fall of temperature for equal times after removal to shade. 



Experiment 11. Effects of Dry Powders. — Prepare two squares from 

 the same piece of leather {e.g. an old shoe). Moisten them both, and 

 apply face powder to one. Which dries more quickly? Repeat after 

 oiling them. Powder a portion of the face or arm daily for a week and 

 compare with the clean portion. 



Experiment 12. Dissect the kidney of an ox or sheep, making out 

 the parts mentioned in the text, p. 26. 



Experiment 13. (In class.) Emergency Drill. — Have one pupil wet 

 an imaginary burn on the arm of another, treat it with flour or soda, and 

 bandage. (See text.) 



The Skin has Two Layers. — The outer layer is called the 

 epidermis ; it is thinner, more transparent, and less elastic 

 than the inner layer, or dermis. The epidermis is com- 

 posed of epithelial cells packed close together (see colored 

 Fig. 1). 



The dermis, or inner layer, is a closely woven sheet of 

 connective tissue (colored Fig. 1) containing a great num- 

 ber of siveat and oil glands, roots of hairs, blood vessels, 

 absorbent vessels (lymphatics), and nerves (colored Fig. 1). 

 The dermis is sometimes called the true skin because it is 

 of greater importance than the epidermis. It is united 

 loosely to the underlying organs by a layer of connective 

 tissue. It is in this layer that fat is stored. The upper 

 surface of the dermis rises into a multitude of projections 

 (see colored Fig. 1) called papiV l<z (singular, papilla). The 

 epidermis fits closely over them and completely levels up 

 the spaces between them except on the palms and the 

 soles. Here the papillae are in rows, and there is a fine 

 c 



