GROWTH IN TIME OF THE TOTAL ORGANISM 



185 



TABLE 10 (continued) 



(/) Explanations of the size-dependence of metabolic rate 



A number of hypotheses have been advanced for explaining the size dependence 

 of metabolism and, in particular, the surface rule. None of these explanations is 

 satisfactory (Kleiber, 1947; BertalanfTy, 1942 and 1951a; BertalanfTy and Piro- 

 zynsky, 1953). The reduction of weight-specific metabolic rate (Oi/g/h.) with 

 increasing body size can be due to either {a) cellular or {b) or ganisniic factors. It may 

 be based upon intrinsic diflferences in the metabolism of cells of smaller and larger 

 individuals; or it may be regulated by factors lying in the organism as a whole. 



(«) If the reduction of specific metabolic rate is due to intracellular factors, 

 a corresponding decrease should be found in the respiration of isolated tissues. That 



Literature p. 253 



