924 METABOLISM. 



According to RUBNER'S rule as to the influence of the surface, which 

 has been recently formulated by E. VOIT, the need of energy in homceo- 

 thermic animals is influenced by the development of their surface when 

 their body is given rest, medium surrounding temperature, and relatively 

 equal protein condition. This rule applies not only to adult human beings, 

 but also to children and growing individuals (RUBNER, OPPENHEIMER, 

 SCHLOSSMANN and MURSCHHAUSER). The surface is the essential factor 

 in determining the extent of exchange of energy. In order to show 

 this we will give here, from a work of RUBNER/ the figures representing 

 the quantity of heat in calories for 1 square meter of surface for twenty- 

 four hours: 



Adult, medium diet, rest 1189 calories. 



Adult, medium die x , work 1399 ' ' 



Suckling 1221 " 



Child with medium diet 1447 



Aged men and women 1099 ' ' 



Women 1004 " 



The variation in the calorific values 2 found by many investigators, 

 which is sometimes not very small, suggests the fact that the surface 

 rule is not alone decisive for the exchange of material in resting animals. 

 Still it is generally considered that it is of the greatest importance in 

 metabolism. 



The more active metabolism in young individuals is apparent when 

 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 3 are of value : 



Age. Weight of Body Urea in Grams. 



in Kilos. Per Day. Per Kilo. 



liyears 10.80 12.10 1.35 



3 



5 



7 



9 



12 



15 



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. 



1 Rubner, Ernahrung im Knabenalter, page 45; E. Voit, Zeitschr. f. Biologic, 41; 

 Oppenheimer, ibid., 42; Schlossmann and Murschhauser, Bioch. Zeitschr., 18 and 26. 

 J See Magnus-Levy, Pfluger's Arch., 55; Slowtzoff (u. Zuntz), ibid., 95. 

 1 Zeitschr. f . Biologic, 16 and 20. 



