666 



PHYSIOLOGY 



TOTAL OUTPUT 



As we should expect in a man who had previously fasted five days, this 

 balance-sheet shows a marked retention of the food taken in, i. e. a marked 

 excess of income over output. Thus of the nitrogen ingested, 13 grm., which 

 is equivalent to 81-3 grm. of protein, was retained; of the carbon, 302 grm. 

 was retained. Of this 302 grm., 42-7 grm. would be contained in the 81*3 

 grm. of protein, so that the rest of the carbon, namely, 259-6 grm., was 

 probably laid down in the form of fat. This would correspond to 339 grm. 

 of fat. Of the salts contained in the ash of the food, 25 grm. were retained 

 in the body. The carbon and nitrogen reappearing in the excreta serve as 

 an index of the amount of metabolism of the foodstuffs which had occurred 

 during the two days. In order to supply the energy requirements of the 

 body during the time of the experiment, 498 grm. of carbohydrate, 59 grm. 

 of alcohol, and 138 grm. of fat had been completely oxidised. The amount 

 of protein used up during this time can be obtained by multiplying the 

 nitrogen of the urine plus 1 grm. of nitrogen of the faeces by the factor 6-25, 

 and is found to amount to 271-9 grm. 



THE ENERGY BALANCE-SHEET OF THE BODY 

 The energy income of the body is measured by the potential energy of the 

 foodstuffs, i. e. the amount of energy which can be evolved, either as heat, 

 work, or in any other form, by the oxidation of the foodstuffs to the end- 

 products which occur in the body. Since it is convenient to have a uniform 

 method of expressing the total potential energy of a foodstuff, we generally 

 express it in calories, and speak of the heat-value of a foodstuff. The 

 heat value of any given food is the amount of large Calories 1 which it 

 evolves on complete combustion with oxygen, and is determined by burning 

 a weighed quantity of the dried foodstuff in oxygen in the bomb calorimeter. 

 The following lu>at values have been obtained for different foodstuffs : 



Substance 

 Lean meat 

 Lard . 

 Butter . 

 Grape sugar 

 Cane sugar 



St.-livh . 



Heat value 

 .V0f>0 (or 5-345 Rulmer) 



9*281 



:;-;<>2 



4-110 



1 A calorie if the .minimi of heat MOQBMiy to NUB6 a gramme of water from 15 C. 

 to 16 C. A large Calorie (printed with a capital C) is the heat required to raise a kilo- 

 graiiuno of water fn:.i 1 .V ( '. to 10' ('., and is therefore equal to 1000 small calorics 



