Biological similitude: statistical and functional relationships in comparative physiology.

A concept of biological similitude based on the distinction between extensive and intensive properties of animals is discussed. This concept provides a theoretical basis for using the power function as a mathematical-physical model whose numerical and dimensional constraints give some insight into the nature of the relationship between body mass and energy metabolism. In particular a theoretically mass-independent expression for energy metabolism is derived that can be used for qualitative intra- and interspecific comparisons of energy metabolism.