Osmotic Properties and Permeability of Cancer Cells I . Relative Permeability of Ehrlich Mouse Ascites Tumor Cells and of Mouse Erythrocytes to Polyhydric Alcohols and to Sodium Chloride *

makes such studies possible. These cells meet the requirements for quantitative determinations of osmotic phenomena and of the related property of permeability : they are obtainable as isolated un injured cells of a single type; they are free to undergo volume changes; their size and shape is such as to permit accurate measurements. Such characteristics are shared by only a few other types of animal cells, which therefore have been widely used for osmotic studies—notably, erythrocytes and egg cells of certain marine invertebrates (1). Like them, ascites tumor cells can be obtained in large numbers and kept outside the body for hours without undergoing changes. This has several de cided advantages : (a) It permits the use of accu rate optical methods for measuring cell size, such as a diffraction method (6, i@) or, as in the present experiments, a photoelectric method (9, 10). By these means precise measurements can be made rapidly and at short intervals of time, and the course of swelling or shrinking of cells can be fol lowed from beginning to completion. (b) Each measurement gives a statistical average. of cell size, thereby canceling out individual variability. (c) The cells can be measured while in suspension and can be continuously stirred. (d) In the photo