Mathematical expression of the effects of changes in body size on pulmonary function and structure.

The biological meaning of the mass coefficient "a" and mass exponent "b" of the power function relating body mass "M" and a morphometric or physiologic variable "y" is discussed (y = aMb). The mass coefficient represents the effect of intensive or qualitative factors on the considered function or structure. The theoretical mass exponent is a criterion for the constancy of the mass coefficient and the qualitative sameness of the compared animals. The Theory of Homomorphism shows that the power function is a mathematical-physical model for analyzing structure and function in animals of different size.