METABOLISM 577 



of a series of emaciated or corpulent individuals by comparison of their 

 calorie output per square meter of surface with that of normal individuals. 



The determining factor of energy output is undoubtedly the general 

 condition of bodily nutrition the active mass of protoplasm of the body 

 (Benedict). That there is a relationship between the body surface and 

 metabolism is undoubted, but the relationship is not a causal one. At 

 present, therefore, the only safe method to employ in comparing the 

 metabolism of normal and diseased individuals is that called by Benedict 

 "the group method," in which the metabolism of groups of persons of 

 like height and weight is compared, it being assumed that such individuals 

 have the same general growth relations. . 



Benedict, in collaboration with Harris, has carried this idea into effect 

 by the preparation of standard tables which give the values for basal 

 metabolism for both men and women for the commoner ranges of weight, 

 stature and age. The values in the tables are based on the statistical 

 constants of a sufficient number of accurate normal data so that they 

 can be used as the standards for comparison with results obtained under 

 various physiological and pathological conditions. 



Two sets of tables are employed, one for body weight and the other 

 for stature and age, the values of the two tables being added together, 

 and, since women have a lower metabolism than men, sets of tables for 

 both sexes are necessary. To determine whether there is a significant 

 modification of metabolism in clinical cases, it is necessary to compare 

 the actually measured calories with those calculated from the tables on 

 the assumption that the patient is in normal health. It has been found 

 by this method that athletes have a somewhat higher metabolism than 

 untrained persons, and that living on a vegetarian diet does not funda- 

 mentally alter it. 



Influence of Age and Sex 



The energy output is low in the newly born ; it increases rapidly during 

 the first year, reaching a maximum at about three to six years of age, and 

 then rapidly declining to about twenty, after which it declines much more 

 slowly. The decline in the earlier years does not proceed steadily, how- 

 ever, for at the period just preceding the onset of puberty a decided in- 

 crease becomes evident, indicating that at this period the metabolism of 

 the growing organism is being stimulated. Females have a lower energy 

 output than males, and the stimulating influence of puberty is less marked 

 in them. 



In round numbers, 40 C. per square meter of surface per hour is the 

 energy output of normal men, a 15 per cent deviation being considered 

 as decidedly abnormal. The average metabolism of fat and thin subjects is 



