Notwithstanding the fact that much of modern physiology has concerned itself with the maintenance of constancy of the milieu intérieur, a definite lag persisted in the study and understanding of those factors regulating the normal volume and distribution of body fluids. Starling, with his rare insight, had early called attention to the fact that such control must exist,200 and experiments supporting this idea were subsequently reported,1,8 but the implications of the results—far ahead of the conceptual thinking of the time—fell upon soil unprepared for germination.
Historically, several factors contributed to the delayed growth of knowledge of fluid volume regulation. Measurements of body fluid constituents by the standard chemical methods are reported, in the language of chemists, as concentrations, and so accustomed have we become to this method of expression that students frequently find it difficult to associate a normal concentration with a highly abnormal amount of substance in