30 NATURE STUDY REVIEW [9:1— Jan., 1913 



two. How does it now taste? What does the saliva seem to be 

 doing for the starch ? Why ? Now try some of the cooked starch 

 and see if there is any difference in the time it takes till the 

 sweetish taste begins to appear. What do you learn from this? 



3. The mouth in relation to foods other than starch. — (a) 

 Provide each pupil with a small mouthful of clean wheat grains 

 and let him chew until a small mass of "wheat gum" remains 

 that will not dissolve in the saliva. Explain that this is a kind of 

 food that the mouth will not digest. It is called gluten and be- 

 longs to a group of foods called proteids (be sure to pronounce 

 the word in three syllables if you use it at all) such as are digested 

 in the stomach and small intestine. Similarly try a bit of the 

 white of a hard boiled tgg and see if it dissolves in the mouth. 

 Is the white of ^gg a starchy food? Try dried beef also. 



(b) Direct each pupil while at home to put a bit of butter 

 alone in the mouth. Did it dissolve, or did it just melt? Butter 

 belongs to a group of foods known as fats, and these are not 

 digested until they reach the small intestine. 



4. Simple studies of starch. — (a) Does one find much 

 starch in foods and is it present in many foods? There is a 

 liquid we can get at the drugstore called iodine solution that we 

 can easily use to find out whether the various foods we eat con- 

 tain much or little or no starch. Putting a few drops of iodine 

 on bread or potatoes we notice that it turns dark blue, which 

 is a sign of much starch. Thoroughly cooked beans or peas will 

 turn but slightly blue with iodine showing little starch. Raw ap- 

 ple will not turn at all, showing that it has no starch. Try a 

 number of common foods and make a list of those containing 

 much, little and no starch. Is starch present in any great degree 

 in what we eat ? 



(b) Try starch in some form to see if it can be burned. 



(h) HYGIENIC CONCLUSIONS. 



Men who have studied the question of foods very carefully 

 tell us that for adults to live healthily they need to eat six times 

 as much of starchy foods as they do of proteids and of fats. They 

 say that for a day's feed one needs fifteen ounces of starchy 

 food (carbohydrate) to two and a half of proteid and two and a 

 half of fat. That is, for an average meal, one needs a little 

 less than an ounce of proteid and of fat and five ounces of 

 starchy food. Since starch is present in so many foods, do you 

 see any reason why food generally should be thoroughly chewed 



