I n a recent paper it was reported(1) that the fragility of certain mammalian erythrocytes is increased by testicular extract. In the last analysis such a change in erythrocytes signifies an increase in their permeability to hemoglobin. Since there was a certain amount of evidence from the work of Duran-Reynals and others(2) that the effect of testicular extract in enhancing bacterial infection may depend on increased permeability of cells and tissues, it seemed possible that testicular extract may have the general property of increasing permeability, when brought into contact with cells and tissues of various kinds.
In order to test this possibility, it appeared desirable to select a type of cell in which changes in permeability can be measured quantitatively. The egg of the sea urchin was found to be suitable material, and its permeability to water a fundamental property which has been found by Luck6 and McCutcheon( 3) to vary widely under experimental conditions.
Permeability to water is studied by exposing the cell to hypotonic solutions of known osmotic pressure ; in such solutions water enters t,he cell as the result of the difference in osmotic pressure between cell contents and surrounding solution, so that the cell swells. Since the cell is spherical, a diameter is measured, and from this volume is calculated.
lAeknowledgment is made to Dr. Balduiii Luek6, of the University of Pennsylvania, for his very valuable aid in developing this investigation and in the preparation of the manuscript.