THE NATURE OF " PREFORMED WATER "

In the method which Newburgh and Johnston (1, 2) have proposed for the calculation of water exchange, they define the latter as consisting of three components: 1, preexisting water from the external environment; 2, water formed de novo by the oxidation of food stuffs; 3, " preformed water. " This last term is applied to water which already existed as such in the tissues, presumably acting as a solvent for protoplasmic substances in the cells and as both solvent and vehicle in the circulating fluids and extracellular (or interstitial) fluids. This fluid or some fraction of it, they postulate, is intimately associated with protein, fat and carbohydrate (glycogen) in the tissues and is liberated when the latter are burned. Conversely it may be presumed that a fraction of the extraneous water becomes bound when the body content of these substances increases. It has been pointed out (3) in a simple analysis of the form of their mathematical calculations that it may be advisable, for certain purposes, at least, to distinguish this third fraction of water from the others because it belongs i