The appearance of cell-free plasma and “grouping” of red blood cells in normal circulation in small blood vessels observed in vivo 1

Abstract

The appearances of blood flowing at high velocities in fine blood vessels are discussed and are supported by high speed photographs and tracings from series of such photographs. These indicate that blood flowing in the larger arterioles contains loose aggregates or groups of red cells separated by zones of relatively cell free plasma.

As these groups pass into the finer arterioles the blood cells become remarkably deformed and the diameter of the plastic masses, measured in the plane at right angles to the axis of the blood vessel, may be reduced to less than the diameter of a red cell at rest. Discrete red cells are also deformed. It is suggested that such deformation of columns of flowing red cells accounts for the low relative viscosity of whole blood previously observed in fine glass tubes.