A comparison of the respiratory quotients obtained after the ingestion of various sugars is made in table 183, in which the number of experiments, the average post-absorptive values, the average quotients with their time relations, and the total rise are given for each of the sugars studied, only the results obtained with 100 grams being included in this summary. Except in the case of dextrose, the preliminary post-absorptive values were practically the same. That for dextrose, 0.80, was the lowest; the highest average basal quotient, 0.85, was obtained with levulose. The quotients after the ingestion of a carbohydrate show a rise in the first 20 minutes, with dextrose the only exception; the average quotient for dextrose fell from 0.80 to 0.76 during this period. Reference to table 179, from which this figure is drawn, shows that in three of the four experiments included in the average there was a positive decrease in the first period and that in the fourth experiment there was a rise of but one point. The explanation of the exceptional values found with dextrose is not simple. While we are much averse to using the commonplace sentence frequently employed by observers to explain anomalies, i. e., "similar values are found by investigators X, Y, and Z," we should state that this particular point has also been observed and discussed by Durig,1 who says that it is due to an increase in the oxygen consumption and not to a modification of the respiration or an increase in the work of respiration following a preliminary over-ventilation.

After the first 20 minutes the course of the respiratory quotient was much the same for all of the sugars, namely, a distinct increase followed by a decrease. The levulose quotients indicate a much greater and more immediate effect than do the dextrose experiments, the maximum figure in the case of levulose appearing in 40 to 60 minutes, while the dextrose quotients remain essentially at the same level from the first to the fourth hour after the beginning of the experiment, with an absolute maximum from 2 to 2\ hours. With sucrose the maximum effect appeared 20 to 40 minutes after the beginning of the experiment, while with lactose the maximum was found in the same period as with dextrose, i. e., in the 2 to 2\ hour period.

1Togel, Brezina, and Durig, Biochem. Zeitschr., 1913, 50, p. 308.

Table 183. - Average Respiratory Quotients At Intervals Following The Ingestion Of 100 Grams Pure Carbohydrate In Respiration Experiments

It should be remembered that occasionally the quotients given in this table represent values for a single period. For instance, the quotient 0.87 for the sixth to seventh hours with dextrose was obtained in one period (see table 179), while the figure 0.76 given for the fifth to the sixth hours with sucrose is also an individual value. As a rule, however, the quotients given in this table are the average of three or four values and may be considered as reasonably representative of true averages.

The highest absolute values were recorded in the levulose experiments, although the sucrose maximum of 1.03 is but little less than the levulose maximum. It should furthermore be noted that the values for dextrose are lower throughout all of the periods; it is true that the basal value was also lower, but if a correction of 5 points is made in the maximum of 0.92, we should obtain a quotient of only 0.97, which would be measurably lower than the maximum with either levulose or sucrose. Similarly it is clear that the lactose values are measurably lower than those for sucrose or levulose. The average maximum rise with dextrose is 12 points, lactose 14 points, levulose 18 points, and sucrose 21 points. Thus we see that not only do levulose and sucrose exert an effect upon the metabolism which is shown in the quantitative relations of the total measurable metabolic factors (see table 178), but they likewise possess specific characteristics which affect the character of the metabolism, this fact being indicated by a great rise in the respiratory quotient. If we apply a rough correction of 3 points for the conversion of these quotients to non-protein quotients, we should find that none of the quotients would reach 1 with dextrose and lactose, but with levulose the non-protein quotients would be either 1 or above for the first 2\ hours of the experiment, while those for sucrose would appear for the first 1 1/2 hours. The general course of the respiratory quotient shows, therefore, that the effect on the character of the metabolism parallels the effect upon the total metabolism; that is, it is in large part confined to the first hours after the taking of carbohydrate.