Clinical Calorimetry

Since the writing of Paper 41 of this series an unusual amount of work has been published on the subject of the normal metabolism.It is now possible to calculate the normal baseline much more exactly than a year ago and it is therefore necessary to reconsider the whole ques- tion at this early date.The figures representing the average normal metabolism have been changed frequently since the study of the respiratory exchanges began and it may be said that the chief advance has depended on the fact that it has been possible to make the variation in the normal smaller and smaller each year.With the oldest type of large respiration chamber the range of heat production fluctuated enor- mously with the uncontrolled influences of muscular activity and the specific dynamic action of food.With the improved technic of Johansson and with the small apparatus of the Zuntz school these fac- tors were eliminated, but errors due to changes in the calorific factors for O2 and CO2 remained.The normal variation was frequently quoted as from about 2.5 to 5.0 c.c. O, per kilogram and minute with a mean of about 3.5 c.c.Under these conditions a pathological departure from the average normal as great as 40 per cent, might be obscured.In 1914 Coleman and Du Bois2 gathered 48 controls from various sources including seven studied in the Sage calorimeter and gave the figure 34.2 calories per hour as the average heat production per square meter of body surface as determined by Meeh's formula.They pointed out that the normal variation was only plus or minus 10 per cent, if the surface area were used as a standard.In Paper 4 of this series,1 on the basis of a much larger number of controls, we selected the average Submi t t ed