MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 277 



ALCOHOL AS A SOURCE OF HEAT IN THE BODY. 



Iii tin' rest experiments the heat given <>tf from the body was equivalent to the total potential 

 energy of the materials oxidized. This was a> true in the experiments in which alcohol made 

 part of the diet as in those with ordinary food exclusively. The alcohol must therefore have 

 contributed its full quota of heat as truly as did the starch or fat, and all its potential energy was 

 converted into heat within the body. 



In the work experiments the same principle applies, and it follows that unless all the 

 potential energy of the alcohol was converted directly into that of external muscular work part 

 must have been converted into heat within the body. But the total energy of external muscular 

 work was at most the equivalent of 280 calories, while the energy of the alcohol was about 500. 

 Even if all the external work was done at the expense of the alcohol, there would remain 220 calories 

 which must have been transformed into heat within the body. But it is extremely improbable 

 that tin' alcohol supplied all and the ordinary food none of theenergy of external work. In so far, 

 therefore, as the latter came from the ordinary food, more than 220 of the 500 calories of the 

 alcohol must have reached the form of heat within the body. 



We have to do here with the question: Of the total energy which was potential in the alcohol 

 and was made kinetic by its oxidation, how much was transformed directly into heat and how 

 much was first changed to the energy of muscular and other bodily work, internal and external. 

 and was afterwards transformed into heat? This involves two fundamental problems. One is 

 the still unsettled physiological question as to whether the production of muscular energy in 

 general is or is not a direct transformation of potential into mechanical energy. The other is the 

 more specific question as to whether the energy of alcohol is like that of the ordinary nutrients 

 of food in its transformation into muscular energy. Both will be referred to beyond in the 

 discussion of alcohol as a source of muscular energy. Meanwhile it is safe to say that: 



1. Unless all the potential energy of the alcohol was transformed directly into the energy of 

 internal work in the rest experiments or into that of internal and external work in the work 

 experiments, a supposition that seems highly improbable, part must have been transformed 

 directly into heat in the body. 



2. Whether the potential energy was first transformed into muscular energy or not. the whole 

 in the rest experiments and part at any rate in the work experiments reached the form of heat 

 within the body. 



The conclusion is that in all these experiments alcohol was a source of heat for the body. 



ALCOHOL AS A SOURCE OF MUSCULAR ENERGY. 



General considerations. — The question whether or not the energy of alcohol is used for 

 muscular work is not yet definitely answered. The experiments thus far made do not provide 

 means for tracing the energy of the alcohol through the changes it undergoes in the body, and 

 finding how much of it becomes muscular energy. Nor is it easy to devise such experiments. 

 The difficulty is that the potential energy of the alcohol is transformed along with that of other 

 materials oxidized, and there is no known way of separating the kinetic energy which comes 

 from the alcohol from that which is supplied by the carbohydrates or fats or protein. While 

 there i~ no evidence of any differences between the energy from the several sources, the absolute 

 proof that no such differences exist is not yet at hand. 



Back of this is the more fundamental question as to how muscular energy is produced. 

 Concerning this two theories are held. One is that part of the potential energy of the food 

 and body material oxidized is converted directly into the mechanical energy exerted by the 

 muscle. The other is that the contraction of the muscle, by which its work is done, is due to 

 heat. According to this view, practically all of the potential energy is first transformed into heat 

 and a part afterwards appears as muscular energy. If the second view is correct, it is hard to 

 -ee how the heat derived from the oxidation of the alcohol should be in any way different from 

 Vol. 8— No. 6 4 



