Nitrogen Balance, with comparison of income and output, and amount and character of the daily food, etc. 375 The Physical Condition of the Men 434 Strength or Dynamometer Tests 436 Report by Dr. Anderson of the Yale Gymnasium 439 Reaction Time—Report by Dr. Judd of the Yale Psychological Laboratory 442 General Summary; True Physiological Requirements for Proteid Food 454 IV. THE SYSTEMIC VALUE OF PHYSIOLOGICAL ECONOMY IN NUTRITION. Diseases due to Perversion of Nutrition 455 Waste Products of Proteid Metabolism may be Dangerous to Health 456 Origin and Significance of Uric Acid 458 Modification of Uric Acid Excretion by diminishing the amount of Proteid Food 463 Tables showing Excretion of Uric Acid by the three groups of men under observation; Uric Acid per kilo of Body-Weight, etc. 467 V. ECONOMIC AND SOCIOLOGICAL IMPORTANCE OF THE RESULTS 471 VI. GENERAL CONCLUSIONS 474 VII. DESCRIPTION OF ILLUSTRATIONS 477 PHYSIOLOGICAL ECONOMY IN NUTRITION INTRODUCTORY NOTE.—For the benefit of lay readers, _metabolism_, a word frequently made use of, may be defined as a term applied to the collective chemical changes taking place in living matter. When these metabolic changes are constructive, as in the building up of tissue protoplasm from the absorbed food material, they are termed _anabolic_; when they are destructive, as in the breaking down of living matter or in the decomposition of the materials stored up in the tissues and organs, they are termed _katabolic_. Proteid metabolism, or more exactly proteid katabolism, therefore, means the destructive decomposition of proteid or albuminous matter in the living body and is practically synonymous with nitrogenous metabolism, since the entire nitrogen income is mainly supplied by the proteids or albuminous matters of the food. The chief carbon income, on the other hand, is supplied by fats and carbohydrates, such as starches and sugars.