654 JOHN R MUELIN 



a. Influence of Puberty. Andral and Gavarret maintained that with 

 boys the carhon dioxid output suddenly increased at the age of .puberty, 

 while with girls it just as suddenly ceased to increase at this critical point. 

 Sonden and Tigerstedt give the following comparison of the total CO., 

 output for different age groups using that of a man 57 years of age as 100. 



9-12 years 98 



13-19 " 126 



22-25 " Ill 



34-44 " 105 



The combustion in the body of male individuals from 13 to 19 years 

 of age is therefore greater than that of younger or older individuals of 

 the same sex. This coincides with the period of most rapid growth in 

 length (15th year) and the most rapid growth in weight (16th year). 



In a remarkable series of observations on 200 boys ranging from 9 

 to 19 years of age Olin(a) thought she had found, in agreement with 

 Sonden and Tigerstedt, that the CO 2 output whether as total elimination 

 or on the basis of body surface shows a distinct elevation for the age of 

 puberty (14-16) above the general trend of the metabolism for the entire 

 group. Her table given on p. 655, however, does not appear to bear out 

 this conclusion. 



The first work carried out on the same youths just before and just after 

 the attainment of sexual maturity was that of Olmstead, Barr and DuBois. 

 Eight normal boys were studied in the respiration calorimeter when they 

 were twelve and thirteen years of age and again two years later when they 

 fourteen and fifteen years of age. On both occasions the boys were placed 

 in the respiration chamber four or five hours after a very light breakfast, 

 which has been shown with adults to leave the basal metabolism unaffected, 

 and were observed for two or three consecutive hourly periods while lying 

 quietly, but for the most part awake. In the first series of observations 

 the -basal metabolism was found to be 25 per cent higher than the adult 

 level per unit of surface (linear formula), while in the second after 

 puberty had been definitely established in four of the eight subjects the 

 metabolism was on the average only 11 per cent higher than the adult level. 

 Benedict and Talbot very properly criticise these observations as failing 

 to establish definitely by a sufficient number of observations the true basal, 

 and point out that if the quieter periods of the first series be selected the 

 metabolism is very close to that found in the second series. It might be 

 urged further that there were at the time of DuBois' observations scarcely 

 a sufficient number of basal experiments in the literature at ages preceding 

 and following the ages of his subjects to warrant the inference of a distinct 

 rise in metabolism of the prepubescent age above that of adjacent ages. 

 Benedict and Talbot in a few scattered observations on boys and girls of 

 prepubescent age find no such increase but they admit that their experi- 

 ments are not yet sufficient in number to warrant a definite conclusion. 



3. The Influence of Muscular Activity in Children. The extensive 



