Red cells and rouleaux in shear flow.

The rotation and deformation of human red cells and linear aggregates (rouleaux) in dilute plasma suspension were observed in Poiseuille and Couette flow. Single lunideform-led erythrocyte. s and roluleauix rotated in orbits predicted by theory for rigid spheroids. Bending of rouleaux occurred at orientations at which compressive forces act on the particles and the degree of flexibility increased with the number of cells in linear array.