120 



TEXT-BOOK OF PHYSIOLOGY 



corresponding to 20.62 grams of protein, making a total approximately of 

 120 grams of protein. From this it is apparent that an equal amount of 

 protein would have to be introduced into th^e body in order to restore protein 

 or nitrogen equilibrium. 



The carbon dioxid excreted was 910 grams, equal to 248.8 grams of 

 carbon. 1 The chemic composition of carbon dioxid, together with the 

 amount stated, indicates that it is the chief end-product of the metabolism 

 of fat or carbohydrate, or both, and hence from the amount eliminated it is 

 possible to determine in terms of fat or carbohydrate the amounts that 

 would have to be introduced into the body to restore carbon or fat and carbo- 

 hydrate equilibrium. As i gram of C corresponds to 3.66 grams of CO 2 

 and either to 1.31 grams of fat it is apparent that the carbon, 184 grams, 

 or carbon dioxid, 676 grams, eliminated corresponds to 242 grams of fat 

 metabolized; again as i gram of C or 3.66 grams of CO 2 corresponds to 

 2.25 grams of starch, it is apparent that the carbon or carbon dioxid elimi- 

 nated corresponds to 416 grams of starch. From these figures it is evident 

 that an equal amount of fac or starch would have to be introduced into the 

 body to restore the carbon or the fat or carbohydrate equilibrium, an amount 

 which in either case would be larger than could be readily disposed of by the 

 digestive apparatus and the assimilative capacities. Since the carbon dioxid 

 comes from both fat and starch or sugar, it is difficult to determine the per- 

 centage that comes from the metabolism of the fat and the percentage that 

 comes from the carbohydrate. From observation of the dietetic habits in 

 different countries and of the results of metabolism experiments, it has been 

 deemed advisable to apportion the fat to the carbohydrates in the ratio of i 

 to 3.5 to i to 7. In the foregoing table Vierordt regarded 90 grams of fat 

 and 330 grams of starch sufficient to restore the losses sustained. 



The carbon dioxid excreted also indicates the amount of oxygen utilized 

 in the oxidation of the carbon and the surplus hydrogen of the fats and hence 

 the amount of oxygen that must have been absorbed from the air in the lungs. 

 The amount of oxygen stated in the table is, however, mainly an inference 

 and determined by deducting the loss in weight of the subject of the experi- 

 ment from the combined weight of the CO 2 and the water eliminated. The 

 salts are balanced to a greater or less degree, day by day, by the salts intro- 

 duced in the foods. The excess of water discharged, 296 grams, beyond 

 that taken into the body arises from the union of oxygen with the surplus 

 hydrogen of the fats. 



The following balance table, as given by Ranke, shows the relation 

 of the nitrogen to the carbon in the average mixed diet and in the excretions 

 of a man weighing 70 kilograms, in a condition of nutritive equilibrium: 



1 It must be remembered however that of the CO 2 eliminated a portion arises from the oxidation 

 of the carbon-holding residue of the protein, an amount in this experiment of approximately 64 

 grams ; which would yield 234 grams of COz. The remainder of the CO2, 676 grams, arose from 

 the oxidation of the fat and carbohydrate ingested. 



