WORKS BY THE SAME AUTHOR: Published by D. Appleton & Company. The Physiology of Man; designed to represent the Existing State of Physiological Science as applied to the Functions of the Human Body. Volume I., Introduction; Blood; Circulation; Respiration. 1 vol., 8vo, pp. 500. Cloth, $4.50, sheep, $5.50. The same, Vol. II., Alimentation; Digestion; Absorption; Lymph and Chyle. 1 vol., 8vo, pp. 550. Cloth, $4.50; sheep, $5.50. The same, Vol. III., Secretion; Excretion; Ductless Glands; Nutrition; Animal Heat; Movements; Voice and Speech. 1 vol., 8vo, pp. 520. Cloth, $4.50; sheep, $5.50. The same, Vol. IV., The Nervous System. 1 vol., 8vo, pp. 470. Cloth, $5.50; sheep, $5.50. The same, Vol. V., Special Senses; Generation. 1 vol., 8vo, pp. 517. Cloth, $4.50; sheep, $5.50. The same, complete in 5 vols. Cloth, $22.00; sheep, $27.00. A Text-Book of Human Physiology; designed for the use of Practitioners and Students of Medicine. Illustrated by three Lithographic Plates, and three hundred and thirteen Woodcuts. 1 vol., imperial 8vo. Cloth, $6.00; sheep, $7.00. Recherches expérimentales sur une nouvelle fonction du foie, consistant dans la séparation de la cholestérme du sang et son élimination sous forme de stercorine (séroline de Boudet), Paris, Germer Bailière; and New York, D. Appleton & Company, 1868. 1 vol., 8vo. pp. 122. Price $0.75. This work received an "Honorable Mention" with a "Recompense" of 1,500 francs from the Institute of France (Académie des Sciences), in 1869, Concours Montyon (Médecine et Chirurgie). On the Physiological Effects of Severe and Protracted Muscular Exercise; with special reference to its Influence upon the Excretion of Nitrogen. 1871. 1 vol., Svo, cloth. pp. 91. Price $2.00. Manual of Chemical Examination of the Urine in Disease; with brief Directions for the Examination of the most common Varieties of Urinary Calculi. Fifth edition, 1877. 1 vol., 16mo, cloth, pp. 76. Price $1.00. ON THE SOURCE OF MUSCULAR POWER. ARGUMENTS AND CONCLUSIONS DRAWN FROM OBSERVATIONS UPON THE HUMAN SUBJECT, BY AUSTIN FLINT, JR., M. D., PROFESSOR OF PHYSIOLOGY AND PHYSIOLOGICAL ANATOMY IN THE BELLEVUE OF THE COUNTY OF NEW YORK; CORRESPONDENT OF THE ACADEMY OF NATURAL SCIENCES OF PHILADELPHIA, ETC., ETC. NEW YORK: D. APPLETON AND COMPANY, 549 & 551 BROADWAY. 1878. HARVARD COLLEGE LIBRARY GIFT OF LEDYARD WORTHINGTON SARGENT COPYRIGHT BY AUSTIN FLINT, JR., M.D., 1878. PREFACE. Ar the present time, there are few questions relating to physiology, of greater interest and importance than the one which is the subject of this essay. Since the publication of the experiments of Fick and Wislicenus, in 1866, a large number of observations have been made, which are brought forward as evidence that the muscular system of a fully-developed man or other animal is simply a perfected mechanical apparatus, like an artificially-constructed machine, which accomplishes work, not at the expense of its own substance, the material consumed being restored by food, but by using the food itself, the force-value of which can be accurately calculated, as we can calculate the dynamic value of the fuel consumed in a steam-engine. These observations have led some physiologists to |