Since the publication of Paper 5 of this series the so-called "Linear Formula" has been used in the study of a large number of individuals.Practically all of the subjects of respiration experiments in the Sage calorimeter have been measured in this way, and in addition Means1of Boston has used it as a factor in determining his normal base line of metabolism and the extent of the pathological variations.Means has found that the range of normal variation from the average is smaller and that the apparent depression of metabolism in obesity is much less marked when the linear formula, instead of Meeh's formula, is used to determine surface area.The accuracy of the linear formula has been shown in Paper 9 of this series.In order to correct the slight error in the factor for the arms, and also in order to clear up a few points in the measurements which may cause confusion, it seems best to repeat the formula and show the bony landmarks by diagram (Fig. 1).Some difficulty has been experienced in locating the superior border of the great trochanter in fat subjects.This landmark is the starting point of the measure¬ ment "O" which represents the length of the thighs.If we employ another factor we can use the new measurement "W," the distance from lower border of the patella to the upper border of the pubes, a point already located in the measurement "L."In taking this measure¬ ment, however, one must be careful to have the legs straight and the knees, heels and great toes touching.It is better to take all measure¬ ments from a footboard with the subject lying down,2 determining dis¬ tance from soles of feet to lower border of patella, to upper border of