Although the basal values for the respiratory quotients for the calorimeter experiments were not secured in all cases on the same day, quotients considerably above 0.90 were frequently obtained in the food experiments, which led to the reasonable assumption that there was a pronounced rise in this relationship, since the respiratory quotient for normal individuals in the post-absorptive condition is not far from 0.81 to 0.83. In the respiration experiments a careful study of the respiratory quotients for short periods could be made; these have been recorded in tables 179 to 182 and show the time relations as well as the height of the quotients. In these tables we are considering only the quotients obtained in experiments with 100 grams of carbohydrate.

Dextrose

The respiratory quotients for 10 experiments with dextrose are given in table 179. As will be seen from the protocols of these experiments, the post-absorptive value for the respiratory quotient was in practically every case an average of two or three reasonably agreeing periods. These values ranged from the low quotient of 0.70 to 0.87 with an average of 0.80. If we study the course of the respiratory quotient in the experiments, we find that shortly after the carbohydrate was given there was in practically every case a pronounced tendency for the quotient to reach a maximum about the second or third hour, and to fall off thereafter. It should be remembered, in studying these quotients, that each value depends upon the determinations of a single period and hence the general picture alone should be considered. The rise followed by a fall is so clear, however, as to leave no doubt as to the general course of the quotient after the ingestion of dextrose. An examination of the average values shows that within 20 minutes of the beginning of the experiment there was a slight fall from the average basal quotient of 0.80, which was followed by a steady increase until the maximum of 0.92 was reached in 2 to 2 1/2 hours; subsequently there was a tendency for the quotient to decrease.

On examination of the individual experiments, we find that in the two observations with the lowest basal value the maximum height of the respiratory quotient after food was also the lowest. Thus, in the experiment with J. C. C. on December 31, 1912, in which the initial quotient was 0.74, the highest quotient obtained was but 0.81, while in the experiment with B. M. K. on December 30, 1912, with a basal quotient of 0.70, the maximum quotient was 0.79. In these two instances a low glycogen store in the body at the beginning of the experiment can be inferred. This inference is further substantiated by the fact that a few days prior to this test these two subjects were living on a carbohydrate-free diet taken during a series of acidosis experiments.

Table 179. - Influence Of Ingestion Of 100 Grams Dextrose On The Respiratory Quotient In Respiration Experiments

1Average of two quotients, 0.96 and 0.91. 2Average of two quotients. 0.88 and 0.80.

3Average of two quotients, 0.99 and 0.87. 4Average of two quotients, 0.76 and 0.72.

5Average of four quotients, 0.91, 0.85, 0.87, and 0.87 (3 to 5 minute periods). 6Average of two quotients, 0.90 and 0.91 (5 minute periods).

The comparison of the maximum increases in the respiratory quotients for the individual experiments, which is given in the last column, shows the lowest maximum rise to be 7 points above the basal, the highest 17 points, and the average maximum rise 12 points. While the lowest maximum rise was obtained in the experiment with the glycogen-poor subject J. C. C, it should be further noted that in an experiment with C. H. H. on May 1, 1911, in which the initial quotient was 0.87, there was the same rise of but 7 points; the relationship between the initial value and the maximum rise in the quotient is therefore by no means definitely established. In general, however, if the initial value is low, the maximum rise in the quotient is also low.

With dextrose the quotient for only one period was over unity. As it has been shown that the non-protein respiratory quotients are generally two or three points higher than the measured quotients, all values of 0.98 or over would, strictly speaking, represent a non-protein respiratory quotient of unity. Even on this basis but relatively few periods, i. e., 6 periods, show a non-protein respiratory quotient above 1. Respiratory quotients above 1 are commonly considered to indicate the formation of fat from carbohydrate. Furthermore, it is often inferred that the formation of fat from carbohydrate can occur only when the respiratory quotient is above 1, but this we do not believe to be true.

Levulose

The respiratory quotients in 7 experiments with levulose are given in table 180. The post-absorptive basal quotients range from 0.77 to 0.91, with an average of 0.85, somewhat higher than for the dextrose basal quotients, which averaged only 0.80. The general course of any one of the experiments is characteristic of the whole series in that there is an almost immediate rise after the ingestion of the carbohydrate and a tendency after several hours to return to approximately the basal value. The height of the respiratory quotient is much greater on the whole than was obtained with dextrose, as in all but one experiment it reached 1 or over. The lowest basal quotient, 0.77, was accompanied by one of the lowest maxima after food, while the highest basal quotient of 0.91 was followed by the highest observed maximum, 1.11.

Table 180. - Influence Of Ingestion Of 100 Grams Levulose On The Respiratory Quotient In Respiration Experiments

1Average of two quotients, 0.82 and 0.76.

2Average of two quotients, 0.85 and 0.86.

3Average of four quotients, 0.96, 1.07, 1.09, and 1.07 (3 to 5 minute periods).

4Average of two quotients, 1.10 and 1.05 (5-minute periods).

As the time of determining the quotients was not the same in all of the experiments, necessitating several gaps in their arrangement in the table, the averaging of the values is somewhat open to criticism; nevertheless they give a clear picture of the general course of the quotient after the food was taken. The basal value of 0.85 was followed by a rise to 0.99 within 20 minutes of the beginning of the experiments and the maximum rise of 1.04 was obtained in 40 to 60 minutes. Between the fifth and sixth hours the average quotient returned to essentially the basal value. The quotients with levulose are therefore characterized by a sharp rise, with an average maximum rise of 18 points. The maximum quotients ranged in the individual experiments from 11 points above the basal value in the experiment with C. H. H., May 16, 1911, to 23 points with L. E. E. on May 22,1911. The number of respiratory quotients of 0.98 or over, showing a non-protein respiratory quotient above 1, is very large, there being 19 in all. The highest value observed was 1.11 and values as high as 1.09 and 1.07 are of frequent occurrence.

It is clear that there is a specific property of levulose that is markedly different from dextrose in its effect on the metabolism, both quantitatively and (as is now seen) qualitatively. To what extent this is determined by direct and rapid combustion, intermediary processes in transformation to glycogen or fat, or to the stimulating action of intermediary products may not at present be stated with surety.