264 EXPEEIMENT STATION EECOED. 



From these experiments the authors conclude as follows: "Athletes have a 

 somewhat higher metabolism, both per kilogram of body weight and per square 

 meter of body surface, than do the nonathletes with whom we have compared 

 them. . . . 



" The greatly increased proportion of active protoplasmic tissue present in 

 the trained, hardened athlete is alone sufficient to account for the increase in 

 the metabolism, and . . . this is not only an absolute increase, but from the 

 nature of the comparison the metabolism is likewise increased per kilogram of 

 body weight and per square meter of body surface. It would thus apiiear that 

 the increase in the metabolism noted with athletes points strongly toward the 

 earlier conception that the catabolism of the body is proportional not to the sur- 

 face of the body, but to the active mass of protoplasmic tissue." 



A comparison of the basal metabolism of normal men and womien, F. G. 

 Benedict and L. E. Emmes {Jour. Biol. C'hon., 20 {1915), No. 3, pp. 253-262).-^ 

 In this investigation the metabolism of SO normal men and G8 normal women 

 was studied. The computed heat production for 24 hours per kilogram of body 

 weight averaged 25.5 calories for men and 24.9 calories for women. From 

 these observations the general deduction is drawn that the metabolism of men 

 is from 5 to 6 per cent gi'enter than that of women of like weight and height. 



Factors affecting' basal metabolism, F. G. Benedict {Jour. Biol. Chem., 20 

 {1915), No. 3, pp. 263-299, figs. 6). — In this paper the author draws general 

 deductions from a large number of metabolism experiments, which have been 

 made for various purposes, with a view to determining the most important 

 factors affecting basal metabolism. These deductions may be summarized in 

 part as follows: 



" Unquestionably body weight plays an important part. In general, large 

 bodies give off larger amounts of heat than smaller ones, but there is no direct 

 relationship between the total body weight and the total heat production. , . . 



" Careful analysis of metabolism measurements obtained on athletes, normal 

 men and women, and normal and atrophic infants, leads to the conclusion that 

 the metabolism or heat output of the human body, even at rest, does not depend 

 upon Newton's law of cooling, and is, therefore, not proportional to the body sur- 

 face. While certain disturbances in this supposed relationship between the heat 

 production and the body surface may correctly be ascribed to errors in the 

 formulas used for computing body surface, nevertheless the vast bulk of the 

 evidence shows that the variations between metabolism and body surface are 

 far outside of any possible errors in formulas." 



The proportion of inert I)ody fat and active tissue greatly affects basal 

 metabolism, and on this basis is explained the greater metabolism of athletes as 

 conipnred with non;\thletes. " The apparent influence of sex, as brought out 

 in the comparison of the metabolism of men and women, may also be attributed 

 to the greater proportion of inert body fat in the latter, with a consequent 

 smalleK amount of active protoplasmic tissue." 



The effect of height upon basal metabolism is "due without doubt to the 

 fact that the taller individual has the larger amount of active protoplasmic 

 tissue. All these variables deal directly with the mass of the heat producing 

 organism ; i. e., the amount of active protoplasmic tissue." •> 



Another very important factor is the stimulus to cellular activity which is 

 influenced by several factors. " One of these factors is age, and it has been 

 noted that with the growing organism of youth there is a much greater cellular 

 activity than with the adult, and a consequent higher metabolism. It has been 

 brought out, however, that in old age there may be actual atrophy of protoplas- 

 mic material. 



