On the Nature of the Superficial Layer in Cells and Its Relation to Their Permeability and to the Staining of Tissues by Dyes

It is a truism that ere a tissue or cell can stain in a dye the dye and the elements which stain must first be brought into physical contact. The importance of the solubility of the dye in various tissue elements is evident in this connection and has been especially insisted upon by Witt,’ Georgievic? and A. Fischer.3 Nevertheless as regards the normal protein constituents of cellsaand tissues the solubility of the dye in water may probably be considered as a measure of its solubility in the protoplasm of the cells, for even if we consider the protoplasm as a polyphasic system consisting essentially of colloid-poor, waterrich phases in equilibrium with colloid-rich, water-poor phases,* yet the common constituent of these phases is water, by means of solution in which the distribution of the dye may be accomplished. The case is, however, far different for the fatty constituents of cells and for protein and other constituents which may be enveloped in a fatty layer, for in order to stain these the