The universal respiration apparatus measures both the carbon-dioxide excretion and the oxygen consumption, and special records are made of the pulse rate and the respiration rate. The spirometer form of the apparatus also gives a record of the ventilation of the lungs. Although the heat production is not measured by this apparatus, it has been computed by the indirect method from the measurements of the oxygen consumption by means of the factors for non-protein quotients of Zuntz and Schumburg.2 It should be stated that in this computation no correction was made for the heat resulting from the combustion of protein and the actual non-protein quotients were not computed. Magnus-Levy3 has shown that only a slight error of approximately 3 per cent results from neglecting to compute the protein metabolism in indirect calorimetry. The small variations due to the use of the determined quotients in our computations are illustrated by the comparison made in table 125. It has therefore not seemed justifiable to recompute the heat values on the basis of the non-protein respiratory quotient, especially as the results had only a differential significance in this study and the increment above the basal value was the special object of the computations. In most cases, the respiratory quotients as determined are but 2 to 5 points lower than the nonprotein respiratory quotients. With the high-nitrogen diets, the differences are even smaller.

Table 125. - Comparison Of Values For Heat As Computed With Observed And Non-Protein Quotients

(Values per minute).

1See tables 140 and 145, pp. 212 and 213. Diet: 100 grams levulose, with juice of one lemon. 2Basal value; average of 3 periods.

1Carpenter, Carnegie Inst. Wash. Pub. No. 216, 1915, pp. 111 and 227. 2Zuntz and Schumburg, Physiologie des Marsches, 1901, p. 361.

3See Loewy, Oppenheimer's Handbuch der Biochemie, 1911, 4 (1), p. 281; also Magnus-Levy, von Noorden's Handbuch der Pathologie des Stoffwechsels, 1896, 1, p. 207.

In practically all of the observations with the respiration apparatus, the basal value was determined each day just prior to the ingestion of the carbohydrate studied, usually as a result of 2 to 4 well-agreeing periods. From the results obtained with the calorimeter experiments, it was clear that a greatly increased production of carbon dioxide was to be expected after the ingestion of the carbohydrate and that this might persist for some time, but that the increase in the oxygen consumption would probably not continue for a great length of time. Hence most of our respiration experiments were terminated 3 to 4 hours after the ingestion of the carbohydrate; occasionally some experiments were even shorter than this. In no instance were the experiments continued for 8 hours, as was frequently the case in the calorimeter experiments. The periods were usually 15 minutes long, but in one or two experiments they were much shortened for the purpose of studying the rapid fluctuations in the respiratory quotient.1

Only pure carbohydrates were used in the respiration experiments, i. e., dextrose, levulose, sucrose, and lactose. These carbohydrates may be considered as chemically pure products, save that levulose and lactose contain a small percentage of water.2 The amounts given were in practically every experiment either 100 or 75 grams. In many of the experiments the sugars were taken in solution, water and varying amounts of lemon juice being added. As a rule, the juice of one-half or a whole lemon was used, this being approximately 20 or 40 grams.

A large number of subjects were studied and sufficient data secured to draw general deductions, but it should be borne in mind that the individual values must not be considered as indicative of the individuality of the subject or of any particular abnormality. With the universal respiration apparatus, duplicate gas analyses are not made; the measurements of the carbon-dioxide production and oxygen consumption for each period therefore represent only individual determinations. This fact should be especially emphasized, as with practically all other forms of respiration apparatus duplicate gas analyses are the rule.