A digest of metabolism experiments in which the balance of income and outgo was determined / by W.O. Atwater and C.F. Langworthy.

  • Atwater, W. O. (Wilbur Olin), 1844-1907
Date:
1898
Catalogue details

Licence: Public Domain Mark

Credit: A digest of metabolism experiments in which the balance of income and outgo was determined / by W.O. Atwater and C.F. Langworthy. Source: Wellcome Collection.

    11/442 (page 7)
    INTRODUCTION. GENERAL AND HISTORICAL STATEMENTS. The animal organism requires food for a twofold purpose, (1) to fur- nish material for the building and repair of tissue, and (2) to sniipl;y''fuel for the production of heat and energy. In serving as fuel food protects the material of the bod}^ from cousum]ition. The food of animals consists of the so-called nutrients—protein, fat, and carbohydrates, various mineral salts, and water. Similar com- pounds and many others are found in the animal body. The oxygen ol the air, though not strictly a food, is also essential. All of these sub- stances in both the food and the body are made ux) jn-imarily of the elements carbon, hydrogen, oxygen, nitrogen, sulphur, phosphorus, chlorin, silicon, tluoriu, iiotassium, calcium, magnesium, sodium, aiul iron. The changes Avhich these substances undergo in the multiform cleavages and syntheses involved in the processes of digestion, assimi- lation, respiration, and excretion are extremely varied. Tissue is added to the young organism until growth is comiileted. In the performance of the bodily functions, in the wear and tear to which the organism is subjected, tissue is constantly broken down and consumed and new material is as constantly formed to take its place. Tissue is also formed for the storage of reserve material, but to a less extent and mainly in the form of fat, which serves as fuel for yielding energy. The bulk of the fat in the body is therefore to be consid- ered not as an essential jiart of the animal machine, but as fuel stored up in it. Energy is required for the maintenance of the heat of the body and for the performance of its mechanical work. The iiotential energy of both the nitrogenous and nonuitrogeuous ingredients of food and body, i. e., of jirotein, fats, carbohydrates, etc., is transformed into kinetic energy and used in the body. But this service as fuel is performed chiefly by the fats and carbohjnlrates, the carbonaceous as distinguished from the nitrogenous nutrients. When burned in the body the nutri- ents yield energy iii the form of either heat or muscular x>ower. Part of this iiotential energy becomes kinetic in the cleavage of complex comiiounds to simxdcr ones; part is liberated in the xirocesses of oxida- tion. Neither the chemical nor the physical changes which take xilace