140 METABOLISM AND NUTRITION 



that the loss of potential energy was from 2.6 per cent to 11.7 per cent. In 

 this important series the loss in proteid was 3.8 to 11.7 per cent, in fat 1.7 

 to 12.7 per cent, in carbohydrates 0.9 to 5.2 per cent. 



An average figure to express the utilization of energy in the food ought not 

 be placed too low. Suppose we assume that ten per cent of the potential energy 

 is lost, then to supply a man with 3,000 Cal. his diet should have an indicated 

 value of 3,333 Cal. Because of the many analyses necessary, a complete experi- 

 ment on the utilization of foods in the intestine is attended by considerable 

 difficulties. But for all practical purposes it is sufficient to determine the dry 

 residue of the diet and of the corresponding faeces ; for the percentage loss in 

 dry substance, so far as our experience yet goes, varies but slightly from the 

 percentage loss in energy. 



2. THE ENERGY REQUIREMENTS OF AN ADULT 



It is already clear that the requirements of an adult must be determined 

 essentially by the physical work to be done, for work is inseparable from a 

 consumption of substance. Hence we have first to investigate how great the 

 total supply must be for different amounts of work. The problem is simpli- 

 fied materially by excluding the inorganic foodstuffs, for it has been shown 

 that if the diet is sufficient and has the proper constitution in other respects, 

 it will contain also plenty of inorganic substances. 



To determine the minimal requirement, observations must be made on the 

 metabolism in complete muscular rest. Such observations have given the 

 following results: 



A woman, twenty-five years of age, weighing 49.5 kilograms, who was in an 

 hysterical sleep and ate nothing, excreted in twenty-four hours 6.21 g. N and 

 107 g. C = 38.8 g. proteid and 113.2 g. fat, corresponding to 1,228 Cal., or 1.03 

 Cal. per kilo per hour. 



In his calorimetric experiments Atwater obtained as a mean of sixteen deter- 

 minations of the heat loss in sleep (from 1 A. M. to 7 A. M.), the value of 1.03 Cal. 

 per kilo per hour. 



The minimal requirement of the adult man may be placed, therefore, at 

 1 Cal. per kilo per hour i. e., for a man of 70 kg. 1,680 Cal. 



But for patients in a weak bodily condition muscular rest so complete 

 as this never occurs. The skeletal muscles are always moved to a greater 

 or less extent; hence metabolism must be somewhat greater than in sleep. 



The experiments of Pettenkoffer and Voit on individuals at rest give an 

 average (for twenty-four hours) of 2,303 Cal. in fasting and 2,675 Cal. on a 

 moderate diet i. e., 32.9 and 38.2 Cal. respectively per kilo per day. In experi- 

 ments by Sonden and the author on eight resting men between the ages of nine- 

 teen and forty-four years, the metabolism varied from 1,853 to 2,292 Cal., or 

 from 26.3 Cal. to 36.0 Cal. per kilo per day. Eckholm's results on ten students 

 and thirteen soldiers between nineteen and twenty-five years gave a mean result 

 of 35.6 and 37.0 Cal. respectively. From Atwater's calorimetric experiments 

 carried out on three different subjects and covering forty-five days, we get a total 

 metabolism for the resting man of 2,241 Cal. i. e., 32.9, 33.3, and 33.4 Cal. per 

 kilogram. 



