INFLUENCE OF FOOD f)N THE 



101 



the supply of proteid previous to starvation, the greater is the excretion of N 

 during the first few days of starvation. It falls rapidly, however, and after about 

 five days the amount of N eliminated is about the same whatever the compo- 

 sition of the food may have been previous to the experiment (Fig. 43). 



Various circumstances favor the idea that this excess of nitrogen excreted 

 from the body does not come from nitrogenous decomposition products left over 

 from previous days, but that, in the transition from a N-rich to a N-poor diet or 

 to fasting, a certain quantity of the proteid stored in the body undergoes decom- 

 position until the organism has adapted itself to the diminished supply of proteid. 



60 



30 



20 



TO 



gm. 

 Urea 



Day: 



FIG. 43. Three experiments on the elimination of urea by fasting dogs, after Voit. The food 



previous to the fasting period in the experiment consisted of 2,500 g. meat; in 



1,500 g. meat; and in only a little proteid. 



The body places itself in nitrogenous equilibrium when the food contains 

 both nitrogenous and nonnitrogenous substances, in exactly the same way as it 

 does on an exclusively proteid diet. 



The fact that proteid decomposition depends primarily upon the amount of 

 proteid supplied is confirmed in a very interesting way by observations on the 

 nitrogen excretion during the different hours of the twenty-four. The hourly 

 excretion proves to be dependent to a very great extent upon the nitrogen absorp- 

 tion from the intestine. The curves in Fig. 44 will serve as an illustration. 

 They represent the N-elimiriation in the urine in two-hour periods, from 8 A.M. 

 until 12 P. M. The dotted line shows the elimination in fasting, the continuous 

 line, on ordinary diet. 



