Three-dimensional observations of red blood cell deformation in capillaries.

The shape changes of red blood cells (RBCs) flowing in narrow glass capillaries have been studied by the use of two microscopes viewing the cells simultaneously at right angles along a horizontal and a vertical optical axis. The observations show that the primary mode of deformation of RBCs in a narrow capillary is a folding or bending about the longitudinal axis of the capillary rather than a compression and extension of the cells in the plane of the original disk, which has been suggested previously [10].