SURFACE OF BODY AND METABOLISM. 865 



therefore admit of a diminished activity of the cell-mass in the fat boy, 

 but rather an increased activity. According to RUBNER it is not the 

 flesh-mass (protein mass) alone, but its variable functional changes, 

 which determines the extent of decomposition. In women, who generally 

 have less body weight and a greater quantity of fat than men, the metab- 

 olism in general is smaller, and the latter is ordinarily about four-fifths 

 that oi men. 



The essential reason why small animals catabolize relatively more 

 substance than large ones, when calculated per kilo body weight, is that 

 the bodies of smaller animals have greater surface in proportion to their 

 mass. On this account the loss of heat is greater, which causes increased 

 heat production, i.e., a more active metabolism. This is also the reason 

 why young individuals of the same kind show a relatively greater metab- 

 olism than older ones. If the heat production and carbon-dioxide elim- 

 ination is calculated on the unit of surface of the body, we find, on the 

 contrary, as the experiments of RUBNER, RICHET/ and others show, 

 that they vary only slightly from a certain average in individuals of 

 different weights. 



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 homoio- 

 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). 

 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 RUB- 

 NER, 2 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 diet, work 1399 



Suckling 1221 



Child with medium diet 1447 



Aged men and women 1099 



Women : 1004 



The variation in the calorific values 3 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 



1 Rubner, Zeitschr. f. Biologic, 19 and 21; Richet, Arch, de Physiol, 5., (2). 



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

 Oppenheimer, ibid., 42. 



3 See Magnus-Levy, Pfliiger's Arch., 55; SJowtzoff (u. Zuntz), ibid., 95. 



