DEPENDENCE OF WEIGHT OF BODY AND AGE. 923 



things being equal, a small individual of the same species of animal metab- 

 olizes absolutely less, but relatively more as compared with the unit of 

 the weight of the body. With increasing bodily weight the total metab- 

 olism per kilo of animal diminishes, which is true first for individuals of 

 the same species of animals, but also seems to have a certain correctness 

 on the comparison of different species of animals. It must be remarked 

 that the relation between flesh and fat in the body exerts an important 

 influence. The extent of the metabolism is dependent upon the quantity 

 of active cells, and a very fat individual therefore decomposes less sub- 

 stance per kilo than a lean person of the same weight. According to 

 RUBNER 1 the importance of the size of the flesh or cell-mass in the body 

 is overestimated. In his investigations on two boys, one of whom was 

 corpulent and the other normally developed, and on comparing the food- 

 need with that found by CAMERER for boys of the same weight, RUBNER 

 came to theVesult that the exchange of force in the corpulent boy almost 

 completely corresponded with that in the non-corpulent boy of the same 

 weight. By approximately estimating the quantity of fat in the body 

 RUBNER was also able, from the protein condition, to compare the cal- 

 culated exchange of energy with that actually found. The exchange 

 per kilo amounted to 52 calories in the lean and 43.6 calories in the fat 

 boy, while, if the protein condition was a measure, one would expect 

 an exchange of calories of only 35 calories for the fat person. We can- 

 not 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 determine 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 of 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, 2 and others show, 

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

 different weights. 



1 Beitrage zur Ernahrung im Knabenalter, etc. Berlin, 1902. 



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



