236 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



described the indirect action of alcohol has been studied only in so far as (1) through its 

 influence upon the secretion of digestive juices or otherwise it has tended to increase or diminish 

 the proportion of the other food digested, or (2) it has increased or decreased the metabolism of 

 other food or body material. 



The ulterior effects of alcohol do not come within the scope of this particular inquiry, which 

 is limited to its use by the body as nutriment. 



THE QUESTIONS ACTUALLY STUDIED. 



It appears then that whatever value alcohol may have for nutriment must depend upon its 

 ablity to serve as fuel for furnishing energy to the body. Accordingly the main question 

 proposed for study is this: What is the value of alcohol for fuel and how does it compare in this 

 respect with sugar, starch, fats, and other nutrients of ordinary food materials; A collateral 

 question is the effect of alcohol upon the proportions of nutrients digested from the food with 

 which it was taken. 



Experimental research has shown several ways in which the ingredients of ordinary food and 

 body material serve as fuel. They are oxidized in the body; in the oxidation, their potential 

 energy becomes kinetic and is thus made useful to the body; part of this kinetic energy appears 

 as heat; another part appears as muscular work; in yielding energy by its own oxidation, food 

 protects the material of the body and of other food from consumption. We have then to 

 consider how alcohol compares with the ordinary fuel ingredients of the food in these ways. 



It is clear that the main problem is that of the metabolism of energy in the body. Accord- 

 ingly, while the experiments here described bear upon the use of alcohol in each of the ways just 

 mentioned and upon collateral topics also, the fundamental question studied has been this: To 

 what extent is the energy of alcohol transformed and utilized in the body like the energy of the 

 nutrients, especially the fats and carbohydrates, of ordinary food materials; 



In studying these questions we go down to one of the fundamental principles of material 

 science. The plan of the whole inquiry is based upon the principle that the chemical and physical 

 changes which take place in the body, and to which the general term metabolism is applied, occur 

 in obedience to the laws of the conservation of matter and energy. That the law of the conservation 

 of matter applies within the living organism, no one would question. It might seem equally 

 certain that the metabolism of energy within the body takes place in accordance with the law of 

 the conservation of energy, in experiments with men in the respiration calorimeter described 

 be3 T ond, the close agreement between the income and the outgo of energy in the body, under various 

 conditions of work and rest, may be regarded as practically demonstrating that the law holds in 

 the living organism. Such demonstration hail, indeed, been approximated by earlier investi- 

 gations, notably those of Rubner with dogs. 



APPARATUS AND METHODS OF INQUIRY. 



The experiments here described were made with a respiration calorimeter especially devised 

 for research of this kind. The apparatus serves to measure the materials received and given off 

 by the body, including the products of respiration, and is thus a " respiration apparatus." It also 

 serves to measure the heat given off by the body and hence is a form of calorimeter. To indicate 

 this twofold purpose it is called a "respiration calorimeter." The apparatus and methods of its 

 use have been described elsewhere;" a brief description will suffice here. 



"In the following bulletins of the Office of Experiment Stations of the United States Department of Agriculture: 

 No. 44, Report of Preliminary Investigations on the Metabolism of Nitrogen ami Carbon in the Human Organism with 

 a Respiration Calorimeter of Special Construction, by W. < >. Atwater, Ph. I)., C. I). Woods, B. S., and F. G. Benedict 

 Ph. D. ; No. 63, Description of a New Respiration Calorimeter and Experiments on the Conservation of Energy in the 

 Human Body, by W. O. Atwater, Ph. D., and E. B. Rosa, Ph. D., pp. 94; No. 69, Experiments on the Metabolism 

 of Matter and Energy in the Human Body, by W. < >. Atwater, Ph. D., and F. G. Benedict, Ph. D., with the 

 cooperation of A. W. Smith, M. S.. and A. 1'. Bryant, M. S.. pp. 1 12; No. 109, Further Experiments on the Metab- 

 olism of Matter and Energy in the Human Body, by W. ( >. Atwater, Ph. D., and F. G. Benedict, Ph. D., with 

 the cooperation of A. P. Bryant, M. S., A. W. Smith, M. S., and J. F. Snell, Ph. D. 



