406 GENERAL NUTRITION 



consumed entirely or are deposited in the body as fat, leaves their 

 oxidation and discharge as oxidation-products the only alternative. The 

 oxidation of proteids has already been considered. As regards the car- 

 bohydrates, if it can be shown that alcohol normally exists in the blood, 

 even in very small quantity, the idea that these matters are slowly 

 passed from the liver as sugar into the general circulation and are then 

 converted into alcohol, which is promptly oxidized, is worthy of serious 

 consideration (see page 393). Such a theory explains the destination 

 of the carbohydrates and their relations to calorification. There can 

 be no doubt that in certain cases of fever, alcohol administered in large 

 quantity may be oxidized and "feed" the fever, thereby saving con- 

 sumption of tissue. 



In a series of observations made in 1879 (Flint), ft seemed impossible 

 to account for the heat actually produced in the body and expended as 

 force in muscular work etc., by the heat-value of food and of tissue 

 consumed. The estimates of heat-production, made by the direct 

 method, were then adopted; but even the indirect estimates which 

 were much less presented difficulty, though in a less degree. In 

 these observations it was shown that water was actually produced in the 

 body, in quantity over and above that contained in food and drink, during 

 severe and prolonged muscular work. It was also shown that water 

 was produced in considerable quantity during twenty-four hours of 

 abstinence from food. It has been shown by Pettenkofer and Voit that 

 " the elimination of water is very much increased by work, and the 

 increase continues during the ensuing hours of sleep." As regards the 

 oxidation of hydrogen in this formation of water, it is probable that 

 the hydrogen of the tissues is used and that the matter thus consumed is 

 supplied again to the tissues in order to maintain the physiological 

 status of the organism. Adding the heat-value of the water thus formed 

 to the heat-value of food, there is little difficulty in accounting for the 

 heat and force actually produced and expended. 



The demonstration that water is actually formed within the organism 

 under certain conditions not only completes the oxidation-theory of the 

 production of animal heat, but it affords an explanation of certain physio- 

 logical phenomena that have heretofore been obscure. It it well known, 

 for example, that a proper system of physical training will reduce the 

 fat of the body to a minimum consistent with health and strength. This 

 involves a diet containing a relatively small proportion of fat and liquids, 

 and regular muscular exercise attended with profuse sweating. Mus- 

 cular work increases the elimination of water, while it also exaggerates 

 for the time the calorific processes. Muscular exercise undoubtedly 

 favors the consumption of the non-nitrogenous parts of the body, and 



