PHYSIOLOGY: F. G. BENEDICT 
109 
in proportion and there was no obvious disproportion between body/ 
weight and surface area. During the fourth week of the fast there was 
a distinct tendency for the metaboKsm to rise, accompanied by a meas- 
urable increase in the pulse rate. Thus the tendency for the prolonged 
fasting to depress the metabolism was actually overcome by some un- 
known stimulus increasing the cellular activity of the remaining body 
substance, ultimately resulting in a positive increase in the basal metab- 
olism during the last week of fasting. 
Two other factors have been experimentally demonstrated in this 
laboratory as influencing the metabolism. One of these is the char- 
acter of the preceding diet, it having been shown that when a carbo- 
hydrate-free diet is eaten an acidosis is developed which distinctly in- 
creases the cellular activity and results in a very noticeable increase 
in the basal metabolism. The second factor is the marked after-effect 
of severe muscular work, such work causing the pulse rate and the basal 
metabolism to remain at an increased level for many hours after the 
cessation of the muscular activity. This may logically be ascribed 
to a stimulus to the protoplasmic tissue, resulting in a higher metabolic 
plane. 
From the evidence cited, therefore, it may be concluded that there 
is no direct relationship between total body weight and total heat pro- 
duction, that the metaboHsm or heat output of the human body, even 
at rest, does not depend upon Newton's law of cooling, and is there- 
fore independent of the surface area. The observations on athletes, 
the comparison of normal men and women, and of atrophic and nor- 
mal infants indicate that the proportion of active protoplasmic tissue 
plays an important role. Perhaps the most striking factors causing varia- 
tions in the stimulus to cellular activity are age, sleep, prolonged fast- 
ing, character of the diet, and the after-effect of severe muscular work. 
From the evidence gathered with the various subjects studied it is 
clear that the basal metabolism of an individual is a function, first, 
of the total mass of active protoplasmic tissue, and, second, of the stimu- 
lus to cellular activity existing at the time the measurement of the metab- 
olism was made. 
The detailed report of this investigation has been transmitted to the 
Journal of Biological Chemistry. 
