Cooking also improves or develops flavors in food, especially in animal foods, and thus makes them attractive and pleasant to the palate.  The appearance of uncooked meat, for example, is repulsive to our taste, but by the process of cooking, agreeable flavors are developed which stimulate the appetite and the flow of digestive fluids.

Another important use of cooking is that it kills any minute parasites or germs in the raw food.  The safeguard of cooking thus effectually removes some important causes of disease.  The warmth that cooking imparts to food is a matter of no slight importance; for warm food is more readily digested, and therefore nourishes the body more quickly.

The art of cooking plays a very important part in the matter of health, and thus of comfort and happiness.  Badly cooked and ill-assorted foods are often the cause of serious disorders.  Mere cooking is not enough, but good cooking is essential.

Experiments.

Experiments with the Proteids.

Experiment 31.  As a type of the group of proteids we take the white of egg, egg-white or egg-albumen.  Break an egg carefully, so as not to mix the white with the yolk.  Drop about half a teaspoonful of the raw white of egg into half a pint of distilled water.  Beat the mixture vigorously with a glass rod until it froths freely.  Filter through several folds of muslin until a fairly clear solution is obtained.

Experiment 32.  To a small quantity of this solution in a test tube add strong nitric acid, and boil.  Note the formation of a white precipitate, which turns yellow.  After cooling, add ammonia, and note that the precipitate becomes orange.

Experiment 33.  Add to the solution of egg-albumen, excess of strong solution of caustic soda (or potash), and then a drop or two of very dilute solution (one per cent) of copper sulphate.  A violet color is obtained which deepens on boiling.

Experiment 34.  Boil a small portion of the albumen solution in a test tube, adding drop by drop dilute acetic acid (two per cent) until a flaky coagulum of insoluble albumen separates.

Experiments with Starch.

Experiment 35.  Wash a potato and peel it.  Grate it on a nutmeg grater into a tall cylindrical glass full of water.  Allow the suspended particles to subside, and after a time note the deposit.  The lowest layer consists of a white powder, or starch, and above it lie coarser fragments of cellulose and other matters.

Experiment 36.  Examine under the microscope a bit of the above white deposit.  Note that each starch granule shows an eccentric hilum with concentric markings.  Add a few drops of very dilute solution of iodine.  Each granule becomes blue, while the markings become more distinct.

Experiment 37.  Examine a few of the many varieties of other kinds of starch granules, as in rice, arrowroot, etc.  Press some dry starch powder between the thumb and forefinger, and note the peculiar crepitation.