Page:First course in biology (IA firstcourseinbio00bailrich).pdf/557

 CHAPTER VII

FOOD AND DIGESTION

Experiment 1. Tests for Acid, Alkaline, and Neutral Substances.—Repeat tests described in General Introduction.

Experiment 2. Test for Starch.—See General Introduction.

Experiment 3. Test for Grape Sugar.—See General Introduction.

Experiment 4. Test for Proteid.—See General Introduction.

Experiment 5. Test for Fats.—See General Introduction.

Experiment 6. Human Teeth.—Study the form of teeth from every part of the mouth. Get a handful from a dentist. Break some of the teeth to make out their structure. Classify them. Draw section, enlarged.

Experiment 7. Study of the Teeth. (At home.)—Sit with the back to the light and look into a mirror, with the mouth wide open. Do you see the four kinds of teeth named in text? Which are fitted for cutting? Which for grinding? Are any suited for tearing? Are any of the teeth pointed? What is the difference in the bicuspids and molars? Are there any decayed places? Are the teeth clean? Are the so-called canine teeth so long that they project beyond the line of the other teeth, as they do in a dog? Do the edges of the upper and lower incisors meet when the mouth is closed, or do they miss each other like the blades of scissors? How many roots has each lower tooth? (See Fig. 92.). Which tooth has the longest root?

Experiment 8. Structure of Mammalian Stomach.—Get a piece of tripe from the market. Study its several coats. The velvety inner coat is covered with mucous membrane. (Photomicrograph, Fig. 95.)

Experiment 9. Model of Human Food Tube.—Make a model of the food tube out of yellow cambric, giving to each organ its correct size. Follow the dimensions given in text.

Necessity for Foods.—Growing plants and growing animals need new material to enable them to increase in size or grow. Plants never cease to grow while they live; most mammals attain their full size in one fifth of the time