RETENTION OF PROTEID IN THE BODY 121 



formulate any definite law from these experiments, but they appear to indicate 

 that a large daily sparing of proteid depends not only upon the absolute quan- 

 tity of meat, but is best attained when the supply of fat in proportion to the 

 supply of meat is relatively large. 



But we are concerned not so much with the conditions for a large daily 

 deposit of proteid, as with those which insure a large aggregate deposit. It 

 may well *be that with a certain combination of meat and fat the daily 

 deposit of proteid would be high, but would continue for only a few days; 

 while with another combination the deposit per day would be less but would 

 hold out longer, so that the total deposit would be greater in this case than 

 in the first before N-equilibrium sets in. 



It appears in fact from Voit's observations that it is not the greatest supply 

 of proteid which brings about the greatest total deposit. With 1,800 g. of meat 

 and 250 g. of fat N-equilibrium appeared in one case after seven days, and in 

 this time there was a total retention of 854 g. of " flesh " ; with the same animal 

 on 500 g. meat and 250 g. fat, N-equilibrium did not appear within thirty-two 

 days, but during this time not less than 1,794 g. " flesh " was laid on. With 

 this combination the storage of proteid was very evenly distributed over the 

 entire period: in the first twelve days the mean daily deposit was 71 g., in the 

 following ten days 42 g., and in the last ten days 52 g. 



In order to obtain the greatest total deposit of proteid in the body, just 

 as for the largest daily deposit, it appears to be best, therefore, to give a rela- 

 tively large quantity of fat in proportion to the quantity of meat. It is 

 evident, of course, that the supply of proteid must not fall below a certain 

 limit. 



The carbohydrates bear the same relation to the retention of proteid as 

 does fat, with the exception only that their proteid-sparing power is much 

 greater than isodynamic quantities of fat. 



This superiority of carbohydrates is shown in a very suggestive way by the 

 experiments of Landergren. He gave an adult man an almost N-free diet, con- 

 sisting (after deduction of the loss by faeces) of 1.6 g. proteid, 738 g. carbo- 

 hydrate, and 17 g. alcohol, yielding altogether 45.2 Cal. per kilogram of body 

 weight. On this diet the nitrogen excretion in the urine fell from 12.8 g. on 

 the day before the experiment to 3.8 g. on the fourth day of the experiment. 

 From the fifth day on the carbohydrates were almost entirely excluded, and 

 instead an isodynamic quantity of fat was given (a net supply of 304 g. fat, 

 2.1 g. carbohydrate, and 30.4 g. alcohol, yielding altogether 43.7 Cal. per kilo- 

 gram). On this diet the nitrogen excretion in the urine from the fifth to the 

 seventh day rose as follows : 4.3, 8.9, 9.6 g. 



In explanation of these facts it has been supposed that carbohydrates are 

 in a less stable state of equilibrium, owing to their aldehyde or ketone groups, 

 than fat is, and for this reason they are more readily decomposed and thus 

 protect proteid to a greater extent. But this can scarcely be true, for as 

 Landergren has shown, the carbohydrates exhibit their characteristic proteid- 

 sparing effect even when they are fed with a considerable quantity of fat. 

 Thus in an experiment with a net supply (i. e., deducting the loss by the 

 fasces) of 6.5 g. proteid, 143 g. fat, and 308 g. carbohydrate, yielding alto- 



