Subacidity 801 Biliousness 809 Cirrhosis of the Liver 822 Diarrhea 832 Emaciation 845 LESSON XII HARMONIOUS COMBINATIONS OF FOOD AND TABLES OF DIGESTIVE HARMONIES AND DISHARMONIES LESSON XII HARMONIOUS COMBINATIONS OF FOOD AND TABLES OF DIGESTIVE HARMONIES AND DISHARMONIES CHEMICAL CHANGES PRODUCED BY COOKING The application of heat to food is comparatively of recent origin in the evolution of mankind. The use of fire involves a certain amount of mental ingenuity, and could not be practised by man's anthropoid ancestors. Anthropoid animals, whether human or ape, have a great amount of curiosity for the unusual and the new. Man probably began his cooking experiments by soaking hard foods in warm water, then in hot water, or by warming cold foods at his camp-fire. As heat volatilizes the pleasant odorous substance present in many foods, the custom of heating them probably became popular. The habit of cooking spread, as many other novel and interesting customs have spread, from this primitive process to the French chef, regardless of whether the results were beneficial or harmful. The question whether foods should be eaten cooked or uncooked can best be answered by examining the chemical and mechanical changes produced in the process of cooking, and their consequent physiological effects. Cooking may be divided into two classes, namely, MOIST HEAT and DRY HEAT. To illustrate: [Sidenote: Effect of heat on sugars] Sugars are not chemically affected by boiling with water, while starch, cooked with boiling water, or steam, absorbs from three to five times its bulk of moisture, and changes into a soft, pasty, or semi-dissolved mass. Under dry heat, sugars are converted into a brown substance, known as caramel, while starch cooked under a temperature of 300° to 400° of dry heat, is changed into a dextrin, of which toast and zwieback are examples. [Sidenote: Effect of heat on fats] Fats are not changed chemically by moist heat; that is, by being boiled in water, but the globules are melted and the hot fat spreads in a film over other material which may be present. In dry heat, fats are chemically decomposed, forming irritating vapors. The odors of frying fat are due to the presence of small quantities of these decomposition products. In larger quantities, and with greater heat, these substances are exceedingly irritating to the mucous membrane of the stomach and the intestines. [Sidenote: Effect of heat on proteids]