THE EFFECT OF FOOD ON METABOLISM 633 



than is found during starvation. In the experiment given on p. 627 the 

 average nitrogen output during starvation was about 12 grm. of nitrogen. 

 In Succi, the fasting man, the nitrogen output varied from 11-19 grm. on the 

 fifth day to 2-82 grm. on the twenty-first day. 



DAILY NITROGEN EXCRETION OF Succi IN STARVATION 



Day 



1 



2 



3 



4 



5 



6 



7 



N. 

 17-0 

 11-2 

 10-55 

 10-8 

 11-19 

 11-01 



8-79 



Day 



8 



9 



10 



11 



12 



13 



14 



N. 

 9-74 

 10-05 

 7-12 

 6-23 

 6-84 

 5-14 

 4-66 



Day 

 15 

 16 

 17 

 18 

 19 

 20 

 21 



N. 

 5-05 

 4-32 

 5-4 

 3-6 

 5-7 

 3-3 

 2-82 



Chittenden has shown that in man a perfectly normal nutrition may be 

 maintained on a mixed diet containing about 7 grm. of nitrogen daily. 

 In the cases investigated by Chittenden the energy output of the men could 

 be regarded as normal, corresponding to 32-35 calories per kilo body weight. 

 If the amount of fat and carbohydrate be very largely increased it is possible 

 to maintain nitrogenous equilibrium on even smaller quantities of protein. 

 Thus nitrogenous equilibrium was attained by Siven on a diet containing 

 33 grm. of protein daily ( = 5 grm. of nitrogen), but in this case the carbo- 

 hydrates and fats were increased to such an extent that the man was taking 

 in 78-5 calories per kilo per day. These results suggest that the qualitative 

 metabolism of the body is determined by the relative amount of food- stuff 

 supplied to the body and circulating in its juices at any given time, and that 

 preponderance of one food-stuff will tend to excite the cells of the body to 

 the utilisation of this food-stuff at the expense of the other two. That such 

 is the case is shown by a study of the effect of increasing each class of food on 

 the metabolism of the body as a whole. 



EFFECTS OF VARIATIONS IN PROTEIN 



Most of the experiments on the influence of variations in the quantity 

 of protein food have been made on carnivora, such as the dog and cat. Within 

 very wide limits the output of nitrogen is proportional to the intake. This 

 is shown in the Tables (p. 634) by Voit, representing two experiments on 

 dogs. 



In Experiment I the animal had been fed for some days with 500 grm. of 

 meat per diem. The fact that he was excreting nitrogen corresponding to 

 547 grm. shows that this amount was insufficient and that he was not yet in 

 a condition of nitrogenous equilibrium. Each day he was using up 47 grm. 

 of the protein of his body in addition to the 500 grm. supplied in the food. 

 On increasing his food three- fold to 1500 grm. the nitrogenous output was 

 also increased, but a state of nitrogenous equilibrium was not reached until 

 the eighth day of the experiment. During the six days intervening 778 grm. 

 of meat had been retained in the body, i.e. there had been a retention of 



