CONSUMPTION OF FOOD IN THE HEALTHY 7 



352 grams of carbohydrate, containing 19.5 grams of N and 315.5 grams 

 of C, besides 2,016 grams of water. He excreted in complete rest: 



In the urine 17.4 grams N., 12.7 grams C, 1,279 grams water. 



In the feces 2.1 " N., 14.5 " C, 88 " water. 



In the respiration 248.6 " C, 828 " water. 



Total 19.5 " N., 275.8 " C, 2,190 " water. 



The body was, therefore, in IST-equilibrium ; excreted 174 grams of water 

 and retained 39.8 grams of carbon, which corresponds to a deposition of 53 

 grams of fat. 



This method gives us knowledge of the body-albumin during the investiga- 

 tion. This is estimated by means of the nitrogen balance, a method which, 

 since that time, has come into general use. 



One hundred grams of albumin contain 16 grams of N. If- the entire 

 amount of IST due to the decomposition of albumin during the trial period 

 were excreted in the urine, the N figure of the urine need only be multiplied 

 by 6.25 to determine the amount of albumin metabolism. The other N losses 

 of the body are slight. A small portion appears in the feces as a residue of 

 the intestinal secretions and this is sufficiently large to be calculated in each 

 investigation. The other N losses of the body (loss of hair, scales of the 

 epidermis and sweat) are so insignificant that they may be ignored in a trial 

 period lasting twenty-four hours. 



Nitrogen equilibrium is then shown when the food-N = urinary-N" + 

 fecal-N". 



Voit's quantitative method of estimating metabolism also permits us to 

 recognize from the carbon balance whether the body's need of N-free sub- 

 stance has been fulfilled by the food given during the trial period or not. 

 The organism has its very definite calory requirement. With an insufficient 

 administration of nourishment, the body takes a supply of energy from its 

 own material component parts. When, in a body previously in equilibrium, 

 carbon is retained or more excreted than is ingested, a corresponding accumu- 

 lation or loss of fat is indicated. In the form of carbohydrates (glycogen) the 

 body does not accumulate any great supply of energy. 



In the quantitative estimation of metabolism in the clinic it has been 

 necessary as a rule to proceed without determining the carbon balance. This 

 require " the estimation of the total COo excretion in the respired air, which 

 can only be accomplished by means of a large respiratory apparatus such as 

 that of Pettenkofer. Such an apparatus is expensive and very difficult to 

 adjust. As many hours are required to make the experiment, it is incon- 

 venient to employ this apparatus at the bedside. 



To compensate for this, the condition of the body-weight has been em- 

 ployed as a control to determine whether, besides the proteid requirement, a 

 sufficient energy supply for the needs of the organism is present in the food. 

 If there is little variation in the material constituents of the body (albumin, 

 fat and water), this is permissible, especially if the experimental period is 

 not too brief. Instead of trials of twenty-four hours, therefore, trial periods 

 of three to four days are usual in metabolism analyses of this type. 



