An Equation for the Flow of Blood, Plasma and Serum through Glass Capillaries

In mammals, the red cells are smaller than the leucocytes but, when associated in groups (rouleaux or clumps), they will tend to replace theLeucocytes in the centre, thus altering the distribution of concentration, and Poiseuille's fourth-power radius law fails to hold.

Abstract

WHEN blood flows through narrow tubes, the larger suspended particles tend to accumulate in the centre, leaving a zone of plasma near the walls. In mammals, the red cells are smaller than the leucocytes but, when associated in groups (rouleaux or clumps), they will tend to replace the leucocytes in the centre, thus altering the distribution of concentration. This means that Poiseuille's fourth-power radius law fails to hold1. Several authors, notably Fåhraeus2, have stressed the importance of this in large and small vessels in vivo. The significance of intravascular clumping or 'sludging' has been widely discussed by Knisely and his school3 (see also ref. 4).