Metabolic rate and body size: a new view on the 'surface law' for basic metabolic rate.

In larger animals a considerable part of the total body mass (e.g. body water, dissolved substances, mineral and organic deposits) does not consume significant amounts of oxygen. These materials can be considered to form a metabolically inert infrastructure which mainly serves three functions: (1) structural support to the organism, (2) storage of nutrients (building material and energy stores) and (3) transport and distribution of these materials. Considering the transport and support function of the metabolically inert structures and their interconnections it is likely that the infrastructure will basically show some tree-like, branching building plan. The weight of the metabolically inert infrastructure of an organism, can be given by bW/(c+W), in which W = body weight, b and c are constants. With increasing size the weight of the metabolic inert infrastructure increases disproportionably. Experimental data concerning basic metabolic rate (M) in relation to body weight (W) better fit the equation M = a W (1-bW/(c+W), (a = constant) than the conventional power law.