INGESTION OF CARBOHYDRATES. 239 



ment with sugars would be proportional to the increment in the total 

 metabolism, has been confirmed in other laboratories, although Lusk 

 properly states that the differences are not very great. The data deter- 

 mined by Lusk 1 by indirect calorimetry after the ingestion of 50 grams of 

 carbohydrates show that the increase over the basal metabolism during 

 the second, third, and fourth hours was 30 per cent with glucose, 37 per 

 cent with fructose, 34 per cent wi th sucrose, and but 3 per cent with lactose. 

 By direct calorimetry he found a 15 per cent increase with glucose, 24 per 

 cent with fructose, 28 per cent with sucrose, and 4 per cent with lactose. 

 This latter series of values compares more nearly with those observed in 

 our respiration experiments. Perhaps one of the most striking points 

 in a consideration of the data in table 178 for these four sugars is the 

 fact that the carbon-dioxide production, even with pure carbohydrates, 

 is not a suitable measure of the energy transformations. 



The clear superiority of levulose and sucrose over dextrose in influ- 

 encing metabolism is difficult to explain. One may assume that levu- 

 lose has a special action upon cellular metabolism and that it is the 

 levulose moiety of the sucrose molecule that produces the effect with 

 sucrose, and yet one would expect the effect to be quantitatively con- 

 siderably less with sucrose than with levulose if this be true. Unfor- 

 tunately the experiments with the smaller amount of levulose, namely, 

 75 grams, are unsatisfactory and few in number, one of the two being 

 obviously erratic with a larger heat production than in any of the 

 levulose experiments. We are hardly justified, therefore, in drawing 

 definite conclusions regarding the amount of levulose which will pro- 

 duce a maximum stimulating effect. It is conceivable, however, that 

 the effect of the sucrose due to the levulose portion may represent the 

 maximum stimulating effect of levulose. 



On the other hand, we have also to consider the energy due to the 

 hydrolysis of the sucrose molecule, which is assumed to be not far from 

 3.1 per cent. If in the experiments with sucrose we consider that 100 

 grams of sucrose have an energy content of 400 calories, we should expect 

 somewhat over 12 calories to be produced as the result of hydrolysis. 

 Deducting the 12 calories from the average total increment of 25 calo- 

 ries obtained in our sucrose experiments, we find that there are 13 

 calories left which can be attributed to the influence of the separate 

 components, levulose and dextrose, upon the metabolism. Assuming 

 that the 100 grams of sucrose result in the formation of 50 grams each of 

 levulose and dextrose, and using the average increments for 100 grams 

 of these substances of 24 and 18 calories, respectively, which were 

 found in our experiments, we would expect to obtain an effect of 12 plus 

 9 calories, or 21 calories, if the effect is a summation effect. It is clear, 

 therefore, that the explanation of the 25 calories due to the ingestion of 



, Journ. Biol. Chem., 1915, 20, p. 590. 



