The Sickling Phenomenon and Its Bearing on the Problem of Red Cell Structure

In considering the various forms of disk-sphere transformation which mammalian red cells undergo, reference has repeatedly been made to the ideas of Norris, Gough, Teitel-Bernard and others who have suggested that the discoidal form of the cell is the result of an equilibrium between two sets of forces, one expansive, and the other (which includes surface tension) conducing to contraction of the surface (Norris, 1882; Gough, 1924; Teitel-Bernard, 1932; Ponder, 1929, 1934, 1936, 1937, 1939, 1941, 1942 a, b, c; Furchgott, 1940 a, 19406; Furchgott & Ponder, 1940, 1941). When the disk changes into the sphere, we are dealing with a diminution or disappearance of the' expansive force' which is probably due to a modification or even a destruction of a surface ultrastructure, and in the absence of anything to oppose it, the tension at the cell-fluid interface determines that the cell takes up the spherical form in which the surface is a minimum for the volume. As will be seen below, other forces are probably operative in the same direction. A re-establishment of the ultrastructure, with the 'expansive forces' inherent in its molecular arrangement, leads to the transformation of the sphere into the original disk, and the various conditions under which this reversal can be brought about have already been described. We have now to consider a situation in which the ' expansive forces' are so great, or the forces resisting them so small, that the red cell assumes a series of shapes which are characterized by extension, just as the spherical form is characterized by contraction.