On the shape of the erythrocyte.

A model is postulated which attributes the distinctive biconcave shape of the human erythrocyte to a balance of forces acting on the membrane. The forces considered are electrostatic forces due to a charge distribution on the membrane, a hydrostatic pressure difference acting across the membrane, and forces arising from a constant tension in the membrane. A numerical study indicates that the postulated model will produce an equilibrium shape which is very similar to the observed shape of the human erythrocyte.