The Shape of the Mammalian Erythrocyte and Its Respiratory Function

In a note on the shape of the mammalian red cell, Hartridge (1) has suggested that the erythrocyte has a form which is a compromise between that of a sphere and that of an infinitely thin disc. Gas diffusing from the surface of either of these figures would reach the central regions at the same time. The sphere, however, offers a small surface compared to its volume, while in the thin disc, the surface layers forming the envelope would be greatly increased at the expense of the contents. In the disc, moreover, gas would gain access too readily at the ends, so that the peripheral regions would be reached soonest. A body of the shape of the normal red cell meets the difficulties of the problem, for not only is the surface comparatively large for the volume, but the ends are thickened, so that gas diffusing from the surface reaches the central regions in a uniform manner. The red cell being greatly concerned with gas transportation, it is obviously important to consider whether its special shape offers any special advantages. This we propose to do in this short paper, thus following up the suggestion of ttartridge. Consider two equal and isolated sinks, $1 and S=. They will set up lines of flow,