Abstract
A simplified, improved method is described for the determination of volumes of microscopic tissue fragments. Such a method is imperative if measurements of concentrations of small, diffusible molecules are to be performed. A model system has been developed which establishes that the method is accurate within approximately 3%. The method has been applied to the determination of the dry mass per unit volume of fragments of cytoplasm and nuclei of puffer fish supramedullary neurons and of adjacent neuropil. The nuclei of these cells are large and watery and, as expected, their density is only 0.137 kg/liter. The cytoplasmic density is a uniform 0.224 kg/liter. That of adjacent neuropil is 0.195 kg/liter. A novel method is also described which greatly facilitates the handling and transportation of frozen-dried tissue fragments.