In cutis (_c_), or dermis, find capillaries, nerve fibers, fat cells, _two_ sweat glands and ducts, _four_ oil glands (two in section), _two_ hairs, _three_ nerve papillæ, _five_ papillae containing capillaries, _two_ muscles for erecting hairs. In epidermis find flat cells, round cells, and pigment cells. FIG. 2.--WHERE THE FOOD IS ABSORBED (villus of intestine). FIG. 3.--WHERE THE FOOD IS USED (cells with lymph spaces). FIG. 4.--IDEAL SECTION OF MAMMAL. Compare with organs of man (colored Fig. 6). _j_, _j_, jaws; _ol_, nerve of smell; _op_, nerve of sight; _b_, brain; _t_, tongue; _ep_, epiglottis; _oe_, gullet; _th_, thymus gland; _lg_, lung; _h_, heart; _l_, liver; _g_, stomach; _s_, spleen; _p_, pancreas; _k_, kidney; _d_, diaphragm; _m_, muscle; _u_, bladder; _ch_, spinal cord; _v_, vertebræ.] _Experiment 9._ =Does Cotton or Wool protect better from Radiant Heat?=--Lay a thermometer in the sun for ten minutes, first covering 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 texture. 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 composed of epithelial cells packed close together (see colored Fig. 1).