S66 METABOLISM. 



we measure the gaseous exchange as well as the excretion of nitrogen. 

 As example of the elimination of urea in children the following results of 

 CAMERER l are of value: 



e r> j TV"I Urea in Grams. 



Age. Weight of Body in Kilos. p er Day p er Kilo 



years 



10 80 12.10 1.35 



13 30 11.10 0.90 



16.20 12.37 0.76 



18.80 14.05 0.75 



25.10 17.27 0.69 



32.60 17.79 0.54 



35.70 17.78 0.50 



In adults weighing about 70 kilos, from 30 to 35 grams of urea per day 

 are eliminated, or 0.5 gram per kilo. At about fifteen years of age the 

 destruction of proteins per kilo is about the same as in adults. The 

 relatively greater metabolism of proteins in young individuals is explained 

 partly by the fact that the metabolism of material in general is more 

 active in young animals, and partly by the fact that young animals are, 

 as a rule, poorer in fat than those full grown. 



That young individuals show a more active metabolism than adults, 

 follows, as above stated, principally from the relatively greater body 

 surface in the first as compared to the latter. According to TIGERSTEDT 

 and SONDEN, the greater metabolism in young animals depends neverthe- 

 less, also in part, on the fact that in these individuals the decomposition 

 in itself is more active than in older ones. The period of growth has a 

 considerable influence on the extent of metabolism (in man), and indeed 

 the metabolism, even when calculated on the unit of surface of body, is 

 greater in youth than in old age. This view is strongly disputed by 

 RUBNER. He does not deny that differences exist between young and 

 adult individuals which may be considered as a deviation from the above 

 rule; still these differences may, he claims, be dependent upon the work 

 performed, the food, and the nutritive condition. MAGNUS-LEVY and 

 FALK 2 have reported observations which support the conclusions of 

 SONDEN and TIGERSTEDT. 



Nurslings have a behavior different from older children, as with them 

 during the first months of life, and especially the first three days, the 

 metabolism, calculated on the unit of surface, is strikingly low, and 

 lower than with adults. After about two weeks it attains about the same 

 height as adults (SCHERER, FORSTER 3 ) . 



In old age the metabolism is very much reduced ; and even when calcu- 



1 Zeitschr. f . Biologic, 16 and 20. 



2 Tigerstedt and Sond&i, 1. c.; Rubner, 1. c.; and Arch. f. Hygiene, 66; Magnus- 

 Levy. Arch. f. (Anat, u.) Physiol., 1899, Suppl. 



3 Cited by A. Loewy in Oppenheimer's Handb., Bd. 4, 189. 



