RELATION OF MAINTENANCE TO LIVE WEIGHT. 



37 



That large animals katabolize more matter and produce more heat 

 than smaller ones requires no special proof. Experiment shows, 

 however, that the difference is not proportional to size or weight, 

 but that small animals have a relatively more intense metabolism 

 than large ones, the amount being approximately proportional to the 

 body surface, which, of course, is relatively greater in the smaller 

 animal. The existence of such a relation was surmised by various 

 writers, but we are indebted to Rubner 1 for the first quantitative 

 investigation of this question. He determined the fasting katabolism 

 of six clogs whose weights ranged from 3 to 24 kilograms. With 

 the addition of earlier experiments by Voit on a still larger dog, 

 the average results were as follows, the total katabolism being ex- 

 pressed in terms of computed energy. 



Relation of fasting katabolism to weight and to surface — Rwbner and Voir. 



No. of animal. 



Katabolism Katabolism 

 per kilo- 



gram, live Xrtv 



I. .. 



II. . 

 III. 

 IV. 



v.. 



VI. 

 VII 



Calories. 

 36. 66 

 40.91 

 45.87 

 46.20 

 65.16 

 64.79 

 88.25 



Calories. 

 1,046 

 1,112 

 1,207 

 1,097 

 1,183 

 1.120 

 1,214 



While not mathematically constant, the ratio between the fasting 

 katabolism and the surface shows a close approximation to uni- 

 formity, and the same fact has been verified by a considerable num- 

 ber of subsequent experiments. Moreover, it has been shown 2 to 

 be approximately true not only of animals of the same species, but of 

 animals ranging in size from man to domestic fowls, and including 

 also cold-blooded animals. A recent investigation by Kettner 3 upon 

 13 guinea pigs furnishes a striking illustration of this general uni- 

 formity. 



Rubner explains the apparent dependence of the fasting katabolism 

 on body surface as the consequence of the loss of heat from the body 

 due to the cooling action of the environment, which would naturally 

 be proportional to the surface. The fact, however, that not incon- 

 siderable variations have sometimes been observed indicates that 

 other factors than the elimination of heat are concerned, and appar- 

 ently the true cause lies deeper. Not merely the heat production but 

 all the important physiological activities of the body, including the 

 expenditure of energy in locomotion, seem to be proportional to the 



1 Zeitschrift fur Biologie, vol. 19, p. 535. 



2 E. Voit. Zeitschrift fur Biologie, vol. 41, p. 113. 



3 Archiv fur (Anatomie und) Physiologie, 1909, p. 447. 



