ABSTRACT
This chapter provides an overview of the chemical makeup of the body as a whole, the variety of compartments used for convenience in description, and the specific nature of cells. Cells are functional masses of protoplasm, or living matter, that contain or have previously contained a nucleus and are limited peripherally by a membrane. The surface membrane, or plasmalemma, protects the interior from the immediate external environment of the cell and provides a measure of structural support, because many internal parts of the cell are anchored to this membrane by the cytoskeleton. The extracellular water volume can be estimated by the dilution principle and using any compound that is restricted to pools outside of cells. Nearly a dozen markers exhibiting the property are used. The most frequently used marker for the estimation of plasma volume is a dye known as T-1824, or Evan's blue.
