340 FOOD INGESTION AND ENERGY TRANSFORMATIONS. 



fact that the subsequent ingestion of food is made under conditions 

 materially different from those of the procedure followed in practically 

 all our experiments, since after a 24-hour fast the stimulating action of 

 the food must first counteract the depressing effect of fasting. Experi- 

 ments made under these conditions are hardly comparable with those 

 made after only 12 hours without food, and the experiments with a basal 

 value of 24 hours or more of fasting have not been included in the table. 



The fuel values for the diet are at times extraordinarily high. Thus, 

 in the experiment of February 16, 1906, the subject consumed a break- 

 fast of mixed diet having an actual fuel value of approximately 4,400 

 calories. In several other instances the fuel value w r as over 3,300 cal- 

 ories. In general, however, it was not far from 500 to 1,200 calories. 



The total increments, also given in table 249, varied from minus val- 

 ues (which are obviously due to faulty technique, defects in the deter- 

 mination of the basal value, or undue activity in the basal period) to the 

 increment of 334 calories noted in a heavy supper experiment. Of 

 special significance is the relationship between the total increments and 

 the fuel values of the food intake, i. e., the cost of digestion. The 

 highest noted is that of 23 per cent for an experiment with J. J. C. on 

 May 9, 1910, with glidine. Values above 10 per cent appear chiefly in 

 the protein experiments, thus emphasizing strongly the fact that the 

 ingestion of protein causes not only an actual maximum increase in 

 metabolism higher than values obtained with the other nutrients, but 

 a greater proportional increase when compared to the fuel value of the 

 intake. Striking irregularities may be noted, and even with protein 

 we find values under 10 per cent as frequently as above 10 per cent. 



With bananas and sugar the cost of digestion is relatively high in 

 practically all instances, averaging about 7 per cent. In the one experi- 

 ment in which it is low, namely, 3 per cent with F. M. M. on April 8, 

 1 909, there was an ingestion of but 9 grams of sugar. It is possible that 

 the low increment of 19 calories noted on that date in a 3-hour observa- 

 tion may have been due to the fact that the superimposed effect of the 

 cane sugar included in the diet on the other days was here absent. On 

 the other hand, on the days when bananas alone were eaten, the two 

 experiments with Dr. H. showed a cost of digestion of 5 and 7 per cent. 

 Still another experiment made with F. M. M. showed no change. 



While averaging results as diversified as those recorded in this table 

 may appear to be a questionable procedure, yet we may tentatively 

 state that the cost of digestion, or the relationship between the fuel 

 value of the intake and the increase in the heat production due to the 

 ingestion of food is, with carbohydrates, not far from 6 per cent on the 

 average. With fat, aside from the two high values found with cream 

 in the experiments with the subjects A. L. L. and A. H. M. in the spring 

 of 1906, a small cost of digestion is noted, the average being not far from 

 2 per cent. With protein, although wide differences are found, the 



