Fat, absorption, 43, 49 absorption in dogs on low proteid diet, 233, 261 as food, 6 as fuel, 6 as source of energy, 128 as source of energy during work, 58 as source of energy in fasting, 81 composition of, 6 digestion of, in intestine, 36 digestion of, in stomach, 36 fuel value of, 15 fuel value of, metabolized during fasting, 86 hydrolysis of, 36 influence of feeding, on body fat, 44 in foodstuffs, 7 laying on of, from overfeeding, 98, 99 metabolism during fasting, 84, 86 respiratory quotient of, 107 saponification of, 36 specificity of body, 44 synthesis of, 43 utilization of, in dogs on low proteid diet, 261 Fats, availability of, 13 as heat producers, 58 as proteid sparers, 92 Fatty degeneration, 270 Fatigue, relation to low proteid diet, 208 Fenger, S., 293 Fick and Wislicenus, on source of muscular energy, 121 Fischer, Emil, 21 Fisher, Irving, on endurance and low proteid diet, 210 on method of indicating food values, 283 Folin, Otto, theory of proteid metabolism, 144 Food, absorption and utilization of, in dogs on low proteid diet, 261, 262 amounts, required for proteid needs of body, 274 as fuel, 6 as source of energy, 15 availability of, 12 carbohydrates as, 6 character of, in relation to bacterial processes in intestine, 292 consumption and obesity, 270 consumption, relation to prosperity, 160 fats as, 6 fuel value of, 274 of fruitarians, 217 in experiments on proteid requirement, athletes, 198 in experiments on proteid requirement, professional men, 178, 180, 185 in experiments on proteid requirement, soldiers, 198 of Japanese, 219, 221 fuel value requirement of, in dogs, 234, 236, 245–255 influence of, on respiratory quotient, 107 needs of body for, 169 of man, 2 proteids as, 3, 5 real need of body for proteid, 272 relation of appetite to, 162 relation of nutritive value and cost of, 277 requirements, factors modifying, 165 temperance in, 166, 168 value of fruits as, 290 values of, method of indicating, 283 Foods, respiratory, 58 time, remain in stomach, 29, 30 Foodstuffs, carbohydrate in, 7 composition of, 7 fat in, 7 fuel value of, 7 inorganic salts in, 7 organic, 3 plastic, 58 proteid in, 7 water in, 7 Fritz, photograph of, 199 Fruitarians, dietary of, 215 fuel value of food of, 217 proteid consumption of, 217 Fruits, value of, as food, 290 Fuel, carbohydrate as, 6 fat as, 6 proteid as, 6