A comparison of the percentages of greatest increase shown by the four sugars is given in table 173. The average period of observation was practically the same for all of the carbohydrates, although somewhat less in the experiments with sucrose and the 75-gram experiments with dextrose. In all cases the observation was sufficiently long to obtain the maximum effect.

The maximum increments in carbon-dioxide production for 100 grams of dextrose, levulose, and lactose were not far apart, being 25, 32, and 27 per cent, respectively, with an average maximum effect of 28 per cent; with sucrose the maximum increment was 47 per cent. A similar concordant effect is noted for the maximum increment in oxygen consumption for dextrose, levulose, and lactose, the highest values obtained being 12, 11, and 11 per cent, respectively, while with sucrose it was 20 per cent. The maximum increment in heat production was practically the same for dextrose, levulose, and lactose, i. e., from 14 to 15 per cent. With sucrose it was materially greater, 24 per cent. It is thus clear that the maximum effect was markedly different with sucrose from that for any one of the other sugars studied. So far as the time relations are concerned, it appears that not only was the increment very much greater with sucrose, but that the maximum effect also appeared earlier than it did with any of the other sugars. It is possible that the early occurrence of the maximum effect with sucrose may be due to the cleavage which probably occurs immediately after absorption.

Table 173. - Average Maximum Effect Of Carbohydrate Ingestion In Respiration Experiments

1Period from the time when subject finished eating to the end of the last observation, except in eases when the increment of heat ended earlier. See tables 126 to 168 for complete observations.

In all of the experiments either 75 or 100 grams of the sugar were used. With dextrose and levulose the amount of sugar made but little difference in the maximum effect, but there was considerable variation with sucrose. With the smaller amount of sucrose there was a decrease in the maximum effect, which amounted to one-third to one-half of the increment noted in the 100-gram experiments. A simple explanation of this phenomenon is not found. Although the 100-gram experiments with sucrose were on the average somewhat shorter than those with either dextrose or levulose, it is clear that this lowering of maximum increment can not be due to variations in the length of period, for the maximum, which alone is under consideration here, always occurs early in the experiment. It is furthermore clear that the sugar tolerance is by no means exceeded, as 100 grams is not a large amount.

One contaminating feature is the fact that in nearly every case the experiments with the two amounts were not made with the same individuals or with the same groups of individuals. All of the 75-gram experiments with the three sugars were made with either J. J. C. or V. G., and the only 100-gram experiment with these two subjects was that with J. J. C. on March 7, 1911, when dextrose was given. Still it is hardly probable that the fact that the same group of individuals was not used accounts wholly for this difference in effect. It is at least possible that the disintegration of sucrose as a result of cleavage may have produced stimulating substances, such as intermediary acid products, in somewhat larger amounts than those occurring in the preparation of levulose for final combustion or storage in the body. The data do not permit of closer analysis in searching for a cause for this variation. It is evident, however, that following the ingestion of sucrose a considerably greater stimulus to the metabolism may be expected than that occurring with any of the other sugars, at least so far as the maximum effect is concerned.