[An index of erythrocyte rigidity deduced from viscosimetry]

An erythrocyte rigidity index chi defined from viscosimetry, shows significant deviations from normal values in abnormal (hardened red cells, stored blood, sickle cells,...). Moreover, chi-variations vs. plasma viscosity are found in good agreement with the Taylor relation for emulsions and lead to a red cell internal viscosity ni approximately 1-2 cP.