PHYSIOLOGY: F. G. BENEDICT 
107 
In neither of these comparisons is there any tendency to regularity 
or to a grouping of the plots. In other words, the evidence all points 
towards distinct individuaHty with no relationship between the com- 
puted body surface and the heat production. 
With infants the variations in the metabolism on this basis are even 
greater. Thus it was found with normal and atrophic infants that the 
24-hour heat production per square meter ranged from 554 calories to 
1334 calories, while with the strictly normal infants the range was from 
554 to 991 calories. It is obvious that any basis of comparisons which 
involves possible variations of 40% with men, 43% with women and 
80% with normal infants cannot be considered as a physiological law. 
On the other hand, an examination of the available material shows 
that there is a relationship between the heat production and the body 
composition, that is, that any physiological data which imply a differ- 
ence in the proportion of active protoplasmic tissue are invariably 
accompanied by a difference in the basal metabolism. Thus the trained 
athletes showed a distinctly greater metaboHsm than did the non- 
athletic individuals. Furthermore, men with a smaller amount of sub- 
cutaneous fat and a correspondingly greater proportion of active proto- 
plasmic tissue have been found to have a greater metabolism than 
women of the same height and weight. The study of normal and 
atrophic infants showed that with two infants of the same height and 
weight the elder, who would naturally be somewhat atrophic, invari- 
ably had a higher basal metabolism than the normal, well-nourished 
infant. Even with normal adults it can be maintained that of two 
individuals having the same weight but different heights, the taller 
individual will, in general, have the greater proportion of active proto- 
plasmic tissue and the comparison of the heat production of normal 
men of like age and weight but different heights shows that there is 
almost invariably a distinctly greater metabolism with the taller indi- 
vidual. It should be remembered that in all of these comparisons 
only the basal metabolism, measured in complete muscular repose and 
in the post absorptive condition, is used. 
A factor that has heretofore been neglected in considering basal 
metaboHsm is the possibihty that the mass of active protoplasmic tissue 
may functionate with varying degrees of intensity. In comparing the 
metabolism of normal individuals we find that frequently individuals 
with approximately the same weight had very great variations in the 
heat production. This is true of a group of eight men weighing over 80 
kgm. and Kkewise with a group of five men weighing 50 kgm. or under. 
