342 FOOD INGESTION AND ENERGY TRANSFORMATIONS. 



The respiration experiments, summarized in table 250, were primarily 

 designed to study the maximum effect rather than the total increment, 

 and were therefore shorter than the calorimeter experiments. With the 

 exception of one experiment with a mixed diet and one with beefsteak 

 and potato chips, the fuel value of the diet did not exceed 600 cal- 

 ories, this value being much smaller than that of the diets used in the 

 calorimeter experiments. The duration of the increment was also 

 shorter, although it is evident that in many instances the basal value 

 had not been reached at the end of the experimental period. The 

 values given in such cases may be partial rather than maximum. 



The large number of experiments with relatively pure carbohydrates 

 permits a comparison of the values for the different kinds of carbohy- 

 drate. With dextrose it is seen that the cost of digestion ranges from 

 2 to 9 per cent, the average for 14 experiments with 11 subjects being 

 5 per cent. With levulose the total increments ranged from 3 to 9 per 

 cent, and with one somewhat unreliable subject (J. J. C.) rose to 14 

 per cent. The average for 9 experiments with 8 subjects is thus 

 approximately 7 per cent. With sucrose, the total increment varied 

 from 3 to 9 per cent, with an average for 15 experiments with 9 subjects 

 of 6 per cent. With lactose the total increment ranged from 3 to 6 per 

 cent, with an average for 5 experiments with 5 subjects of 5 per cent. 



If we compare the experiments on the basis of the amount of sugar 

 ingested, we find that the average cost of digestion was practically the 

 same for both 100 grams and 75 grams. The only exception was 

 sucrose, which gave an average cost of digestion of 6 per cent for 8 

 experiments with 100 grams and of 5 per cent for 7 experiments with 

 75 grams, the average for all experiments being 6 per cent. 



It is thus seen that the cost of digestion for the carbohydrates studied 

 in these 43 respiration experiments does not differ materially in the 

 proportion of increase, averaging not far from 6 per cent (5.5 per cent 

 to be exact) of the fuel value of the intake. This figure, 5.5 per cent, is 

 almost precisely the average obtained in 22 calorimeter experiments 

 (5.6 per cent), although in those experiments mixed carbohydrates 

 were taken, such as bananas, popcorn, and rice, rather than pure car- 

 bohydrates. 



A relatively large number of respiration experiments were made with 

 the protein-rich food, beefsteak, in which the fuel value 1 ranged from 

 234 to 532 calories, or 790 calories if we include the experiment with 

 beefsteak and potato chips. A strict averaging of these experiments is 

 not permissible, owing to the differences in the time relations. Large 

 increments are noted in several instances with several values for the 



'It should be noted that the beefsteak used in these experiments contained a certain proportion 

 of fat, which supplied from 24 to 37 per cent of the fuel value. Consequently, the cost of digestion 

 of the protein itself is not represented by the figures given. In all probability the true value would 

 be higher. 



