METABOLISM 163 



Of the proteids of the food about 116 g have been consumed. 

 From the hydrogen and oxygen found in this quantity must be 

 subtracted, first, the amount found in the urea and, secondly, the 

 amount of hydrogen which can be oxidized by the oxygen present 

 in the proteid. This leaves 3.5 g hydrogen, which need for their 

 oxidation 28 g of the inhaled oxygen. 



Of the fat of the food about 90 g have been absorbed. For the 

 oxidation of the hydrogen found in it, 75. 5 g of the inhaled oxygen 

 are needed. But of the inhaled oxygen there are remaining only 

 (53 28) = 25 g. Hence only 30 g of fat can have been oxi- 

 dized ; the remaining 60 g have been deposited in the body. 60 g 

 fat contain 45 g carbon, which corresponds quite closely with that 

 found in the experiment (41 g). 



Hence carbon in the form of fat must have been retained 

 in the body, while the carbon of carbohydrates has been 

 entirely oxidized. 



4. There have, then, been deposited in the body 41 g of 

 carbon or about 55 g of fat. But the total increase in body 

 weight was 138 g, hence 83 g more. These 83 g can be 

 present in the body only as water. The balance-sheet of 

 the water shows that 2100 g were taken up and 2315 g 

 given off, hence more water has been given off than taken 

 up. But it must be remembered that in the oxidations 

 taking place in the body, water has been formed. From 

 the oxidized carbohydrates 222 g and from the proteid 48 g 

 and from the fat 30 g of water have been formed, making a 

 total of 300 g. Of this, 215 g [2315 2100] have been 

 excreted, while the remaining 85 g remain in the body. 

 This agrees quite well with the observed figure. 



5 . The balance-sheet of the salts shows that as much salt 

 has been given off as taken up. Hence the body has neither 

 increased nor decreased in salt. 



4. METABOLISM UNDER VARIOUS CONDITIONS 



The extent of metabolism is influenced by: 



(1) The amount and composition of the food; 



(2) The work done and heat lost by the organism; 



(3) The size of the body, age, and sex. 

 I. Influence of food upon metabolism. 



