304 FOOD INGESTION AND ENERGY TRANSFORMATIONS. 



For a true comparison of the results of the different experiments, it 

 is necessary to compare only those in which approximately the same 

 amounts of nitrogen were ingested and with experimental periods of 

 approximately the same length. In many instances the total effect 

 of the food had by no means ceased at the end of the period of observa- 

 tion. In other experiments it was evident that the full effect of the 

 food ingestion was obtained, inasmuch as increments of less than 

 0.5 gram, as well as negative values, were found in the later periods. 

 It was hoped that some information might be obtained as to the rela- 

 tionship between the amount of nitrogen ingested and the increments 

 in the metabolism. Generally speaking, the larger amounts of meat 

 produced the larger increments. This may not hold true, however, 

 when different individuals are used for subjects, as may be seen by a 

 comparison of the experiment with A. W. W., April 6, 1907, in which 

 755 grams of meat were ingested, with that with J. R., December 4, 

 1908, in which 418 grams were taken. Although both of the experi- 

 ments continued for 8 hours, the increment in heat production was 

 slightly more in the second experiment than in the first, but the incre- 

 ment in oxygen consumption and carbon-dioxide production in the 

 experiment with J. R. was about 70 per cent of that in the experi- 

 ment with A. W. W. It will thus be seen that marked irregularities 

 occur in all these experiments, and no constancy was found in com- 

 parisons with different individuals and rarely in comparisons for 

 the same individual. 



It was also hoped that some light could be obtained as to the influ- 

 ence of animal protein as compared with that of vegetable protein. A 

 superficial examination of the data in table 230 shows no material 

 difference in the two classes of proteins in their influence upon the 

 metabolism, but here again the comparisons are complicated by the 

 fact that the experiments are made with different individuals and 

 with different experimental plans. With the purest protein substance 

 used (glidine), the experiments in which the largest amount was given, 

 i. e., 9.70 grams of nitrogen, gave duplicate values for the same subject 

 which were only reasonably satisfactory. Comparing these values 

 with those obtained with beefsteak or with beefsteak combined with 

 potato chips or bread, in which essentially the same amount of nitrogen 

 was ingested, we find that the average values with glidine are slightly 

 higher than those for beefsteak, although even with the same amount 

 of nitrogen the values with beefsteak vary widely. The gluten bread 

 experiments, while complicated by a relatively small amount of animal 

 protein in the form of skim milk, show increments comparable with 

 those obtained with beefsteak. One must conclude, therefore, that 

 these experiments, defective though they are, indicate that there is no 

 clearly defined difference between animal and vegetable proteins in 

 their influence upon the metabolism. 



