CHANGES IX METABOLISM WITH AGE. 109 



Again the probable errors are high because of the small numbers of 

 individuals studied. But one can hardly examine the resul 1 whole 



without reaching the conviction that Magnus-Levy and Falk were in 

 error in concluding that metabolism remains essentially r-on^tant dur- 

 ing adult life. Metabolism decreases throughout adult life, and this 

 decrease is shown by the statistical analysis of their own data to be as 

 evident after correction for the influence of body-size has been made 

 as before. 



Carbon-dioxide production in boys of 10 to 18 years of age has been 

 investigated by Olin, 5 although not under strictly basal conditions. 



One of the objects of the investigations which have been under 

 way on human basal metabolism at the Nutrition Laboratory for a 

 number of years has been the determination of the changes which take 

 place in metabolism throughout the entire period of life. It was the 

 intention to base this investigation upon a number of subjects suffi- 

 ciently large to eliminate the influence of individual variations at dif- 

 ferent ages, and thus to obtain a smoothed curve of basal metabolism 

 of both male and female individuals throughout the entire period of 

 life. Before this program was complete Du Bois 9 combined the 

 extensive data already published from the Nutrition Laboratory with 

 fragmentary data from other sources and attempted to draw a curve 

 of human basal metabolism for the entire period of life. 



In our opinion the time is not yet ripe for an undertaking of such 

 magnitude. While data are still being accumulated for this purpose, 

 and while the results based on 136 men and 103 women are subject to 

 revision as more extensive materials for the earlier and later periods 

 of life are obtained, it seems desirable to analyze in a preliminary way 

 the age changes in the subjects considered in this volume. Certain 

 difficulties in the way of combining different series of measurements to 

 secure a picture of the metabolic activity of the human subjects from 

 birth to death will be indicated in Chapter VIII (p. 243). 



2. STATISTICAL CONSTANTS MEASURING CHANGES IN METABOLISM 



WITH AGE. 



The range of ages of the individuals hi each class, and the statistical 

 constants of age in years, in the several groups of subjects appear in 

 table 36. 



The constants showing the correlation between age and total heat- 

 production in calories per 24 hours are given in table 37. Without 

 exception the values of r, h are negative hi sign, thus indicating that in 



5 Olin, Finska lak.-sallsk. hand!., Helsingfora, 1915, 57, p. 1434. At the time of going to 



press the German report of this research, announced for appearance in the Skandi- 

 navisches Archiv fur Physiologic, is not available and hence analysis of the da- 

 unfortunately now impossible. 



6 Du Boie, Am. Journ. Med. Sci., 1918, 102, p. 7S1. Also Med. Bull. Cornell Tniv.. 1917. 6. 



pt. 2, p. 33. 



