INFLUENCE OF FOOD ON THE METABOLISM 103 



We see that as the amount of proteid fed increases the amount of fat 

 burned decreases, so that, when from 68 to 85 g. of N are supplied (in meat), 

 a small amount of fat is stored in the body. 



Estimation of the total metabolism in Gal. shows that as the amount of 

 proteid in the food is increased, not only is the proteid decomposition in- 

 creased but also the total decomposition, although the latter to a much less 

 extent than the former. With 85 g. N (2,500 g. meat) in the food the total 

 metabolism is about twice as great as in fasting or with 17 g. N (500 g. meat), 

 whereas the proteid decomposition is fifteen times as great as in fasting and 

 about four times what it is with 17 g. N in the food. 



In his experiments on the metabolism of proteid in the body Voit thought 

 he had found that the smallest quantity of proteid with which the body can place 

 itself in N-equilibrium, even when carbohydrates or fats are administered freely, 

 was higher than the quantity destroyed in starvation after the first few days of 

 abstinence. Further investigations have shown, however, that in case the body 

 receives enough nonnitrogenous foodstuffs to enable it to maintain a general 

 equilibrium of substance, the quantity of proteid can be smaller than this. 



From experiments by Hirschfeld, Kumagawa and Klemperer it appeared 

 that N-equilibrium with small quantities of N in the food is only obtained when 

 the total amount of food supplied is much in excess of the usual diet. Thus, 

 while an adult man at rest maintains himself in N-equilibrium on about 100 g. 

 proteid a day with a total energy supply of 32-35 Cal. per kg., in their experi- 

 ments when the supply of proteid was cut down to 43.5 g., N-equilibrium only 

 occurred when the total supply of energy was as much as 47.5 Cal. per kg. ; and 

 with 33 g. proteid only when the total supply reached 78.5 Cal. per kg. 



Siven has shown however that when the N-supply is not cut off suddenly, 

 but is reduced gradually, no such excess of the total supply of energy is neces- 

 sary. Under such circumstances N-equilibrium was obtained, in the case of a 

 man doing a moderate amount of work, with 41.4 Cal. per kg. per day, although 

 the diet contained only 28.3 g. nitrogenous substance. The quantity of actual 

 proteid here was only 12.4 g. In other words, this man received only 0.08 g. 

 total N per kg., of which only 0.03 g. was proteid N", and yet he maintained his 

 N-equilibrium. 



In the fasting experiment on Succi (cf. page 95) from the twenty-first to 

 the twenty-fifth day, 0.09 g. N" per kg. were excreted in the urine. In view of the 

 long abstinence here, it is likely that this nitrogen came exclusively from pro- 

 teid. This being true, it follows that the body can be brought into N-equi- 

 librium with a supply of proteid which is considerably less than the amount 

 destroyed in the later stages of starvation. 



In experiments on dogs with food deficient in proteid but otherwise suffi- 

 cient, I. Munk and Rosenheim observed from the sixth to the eighth week 

 onward various severe disorders in the health, which finally led to the death of 

 the animals some weeks later. According to this, a diet poor in nitrogen when 

 taken continuously would be dangerous even if N-equilibrium were established. 

 The experiments of Jagerroos stand squarely opposed to this view. They show 

 that a dog can live much longer than eight weeks on such a food without exhibit- 

 ing any disturbance to the health, provided he receive his proteid in the form 

 of fresh raw meat. It appears, therefore, that in the earlier experiments it was 

 not the deficiency of nitrogen itself, but the unsuitable character of the food 

 which was the cause of sickness and death. 



