236 Metabolism of Healthy Max. 



On the basis of age, group V (those under 20 years of age) exhibited a total 

 metabolism somewhat above the normal, as indicated by the heat production 

 as well as by the carbon-dioxide production and oxygen consumption, while 

 groups VI (those between 34 and 36 years of age) and VII (those between 54 

 and 59 years of age) are noticeably below the normal. 



From the results presented in table 98, therefore, it is seen that the lean men 

 have the highest metabolism and the short fat men, the lowest; while on the 

 basis of age, the young men have the highest metabolism, the older people, the 

 lowest, and the intermediate age an intermediate metabolism. So far as physi- 

 cal characteristics are concerned, this is wholly in agreement with the idea that 

 the total metabolism is determined in large part by the proportion of active 

 protoplasmic tissue in the body. This would naturally be somewhat larger with 

 lean men than with short fat men, and hence the higher metabolism would be 

 expected with the former group. The tendency for elderly people to accumu- 

 late fatty tissue may likewise account for the variations in metabolism with age. 

 The possibility of protoplasmic tissue having a decreased metabolic activity in 

 old age as pointed out by Magnus-Levy and Falk 1 should also be considered. 

 Those in group VII were men who were distinctly fat. In group VI, 2 in- 

 dividuals were fat; one was an athlete, and the other of normal build. The 

 young men in group V were all free from visible evidence of a large amount of 

 superfluous fat. The results, therefore, plainly do not indicate whether or not 

 age, per se, has an influence on metabolism. 



COMPARISON OF THE METABOLISM OF ATHLETES AND NON-ATHLETES. 



If the assumption is true that the proportion of active protoplasmic tissue 

 present in the body plays an important role in determining the total metabolism, 

 we would expect a priori that trained athletes w r ith a large amount of muscular 

 tissue would show a larger metabolism when at rest than other individuals with 

 similar body-weight and size. Among the subjects experimented with in the 

 respiration chamber were a number of athletes. In table 99 the results are 

 given with these athletes and for purposes of comparison the results with a 

 number of individuals of approximately the same body-weight are also given. 



With the subject D. W. the metabolism, as indicated by the carbon-dioxide 

 production, and heat production, is on the whole considerably lower than that 

 witli the group of non-athletes with which he is compared. With the subject 

 J. C. W. only carbon dioxide and heat were determined, but here again the 

 metabolism is lower than with the four non-athletes with whom he is compared. 

 In the case of the professional athlete N. B., we have a similar condition, 

 namely, a markedly lower excretion of carbon dioxide and absorption of oxygen 

 and a somewhat lower heat production than the average of the group of indi- 

 viduals with whom lie is compared. We have but 2 experiments, 3 hours each, 

 with the athlete H. G., but, as was found with the other 3 athletes, the total 

 metabolism per kilogram of body-weight and per square meter of body-surface 

 seems to be distinctly lower than with subjects of similar body-weight, 



1 Magnus-Levy and Falk., loc. cit., p. 342. 



