In the preceding section special emphasis has been laid upon the maximum increment in terms of percentage of the basal value - in other words, the absolute height to which the basal metabolism can be increased by the ingestion of different carbohydrates. As was pointed out in the consideration of the calorimeter experiments (see page 200), the total increment expressed as a percentage value can have but little significance, as the increase may extend over a considerable period of time and the basal value for this time will be directly proportional to the period; consequently the increment represents a continually decreasing percentage of the basal value. For these respiration experiments, therefore, it is likewise inexpedient to consider the percentage of total increment as referred to the basal value. On the other hand, it is perfectly feasible to compute the total increment in the metabolism. A series of tables has therefore been prepared showing the computed increments for carbon-dioxide production, oxygen consumption, and heat production in the period of observation following the ingestion of carbohydrate.

As already explained on page 151, the increment in heat production for practically all of the respiration experiments has been computed from measured areas representing heat values superimposed on a fasting base-line observed preceding the ingestion of food. The increases in heat production with carbohydrates were obtained in this manner. The increments for carbon-dioxide production and oxygen consumption have been found by a method somewhat different, but yielding practically the same result. As in the case of the plotted area for heat production, values were interpolated for the interval between the time when the subject finished eating and the beginning of the first measured period and for the intervals between the periods of measurement. For the interval preceding the first measured period it was assumed that the increment per minute was one-half that found in the period; for each interval between measured periods the average of the per-minute increments observed in the periods preceding and following the interval was used. Multiplication of the duration in minutes of the intervals and measured periods by the respective increments per minute resulted in totals of either carbon dioxide produced or oxygen absorbed. The totals for periods and intervals, when added together, gave the amounts for the total period in which increment was observed. The computation of the increment began with the time when the subject had finished eating and continued to the end of the last period of the experiment, or through the period in which the increment apparently ceased.

The experiment of December 31,1912, in which the subject J. C. C. took 100 grams dextrose, may be used to illustrate this method of computing the increment (see table 127, page 206). The basal value for carbon dioxide determined on the same day was 187 c.c. per minute. The amount per minute measured in the first period beginning at llh43m a. m. was 196 c.c, or an increment of 9 c.c. per minute for the 14 minutes and 39 seconds of the period; the total increment observed in the period (14.65 X 9) is therefore 132 c.c. Between the time when the subject finished eating and the beginning of this period there was an interval of 8 minutes. Assuming for this interval an increment per minute of one-half that observed in the first period, the total increment for the preliminary interval (8 X 4.5) was 36 c.c. The increase in carbon dioxide for the second period beginning at llh45m a. m. was 16 c.c. per minute, the total for the period (14.92 X 16) being 239 c.c. Between the first and second periods there was an interval of 17 minutes and 21 seconds; assuming a value equal to the average of the per minute increments in the first two periods, the total increase in carbon dioxide for this interval (17.35 X 12.5) was 217 c.c. The results for the remaining periods and intervals are obtained in the same manner and the total increase in carbon dioxide to the end of the sixth period following the ingestion of dextrose was, therefore, the sum of the computed and measured increments (36+132+217+239+316+315+396 +349+550+270+372+195) or 3,387 c.c. The equivalent of this amount is 6.7 grams of carbon dioxide. For the same period of observation, i. e., through the period ending at 2h26m p. m., the increment of oxygen computed and measured was 3 grams and the increase in heat obtained from the measured area of increment superimposed on the fasting base-line was 12 calories.

The total increments for each sugar studied are shown in tables 174 to 177. Although the maximum effect, as we have seen, was obtained usually inside of the first 1 1/2 hours after the ingestion of the sugar, there was a positive increment in carbon-dioxide production, oxygen consumption, and heat production, which was measurable for a fairly long period. Usually the increments in oxygen consumption and heat production persisted for about the same length of time, and thereafter basal values were obtained for both these factors. Frequently the increment in the carbon-dioxide production continued for some time longer; the total excess carbon dioxide is therefore given in a footnote, together with the period of time in which it was obtained.