CHAPTER V. 



CHANGES IN METABOLISM WITH AGE. 



The significance of a knowledge of the relationship of metabolism 

 to age is twofold. 



First, the change of normal basal metabolism with age is in and 

 for itself a problem of prime physiological importance. 



Second, metabolism determinations in the hospital ward have little 

 value as a basis for medical theory or practice except as the constants 

 are interpreted in comparison with those for normal controls. It is 

 important, therefore, that in selecting controls for comparison with 

 pathological cases the influence of the age factor in both health and 

 disease should be fully known. 



Our treatment in this place differs from that accorded the problem 

 by earlier writers in that we have actually determined statistical con- 

 stants measuring the rate of change in metabolism with age during the 

 period of adult, or practically adult, life. 



Ultimately it will be necessary to undertake an examination of 

 the change of physical and physiological characters other than direct 

 or indirect heat measurements as a first step towards a closer coordi- 

 nation of investigation in human metabolism and the results of general 

 biological research. Such coordination should be to the advantage 

 of both the special field of human nutrition and the broader field of 

 general biological theory. 



In this place we shall merely present, and statistically discuss, the 

 available data for human basal metabolism in relation to age. A com- 

 parative examination of age changes in other physical and physiological 

 characters must be reserved for the future. 



I. HISTORICAL REVIEW. 



It was of course inevitable that the problem of the dependence of 

 metabolism on age should be considered in a general comparative way 

 as soon as determinations of the basal metabolism of infants, youths, 

 and adults began to be made. 



While the observations of Andral and Gavarret 1 can not be taken 

 as'basal, we have determined the correlation between age and C0 2 

 production per hour in the men 17 to 102 years of age and in the women 



1 Andral and Gavarret, Ann. de chim. et phys., 1843. 8, 3 ser.. p. 129. 



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