[Measurement of blood viscosity using a rotatory viscosimeter with coaxial cylinders].

The authors describe a microviscosimeter with coaxial cylinders which requires only a small volume of sample. They draw up formulae permitting to obtain in a simplified way, fluid rheograms, in particular for biological fluids. Furthermore, they consider the use of this viscosimeter for the study of the rheological properties of blood and plasma. Thus, at 30 degrees C, the plasma and serum have a newtonian behaviour, whilst the viscosity of total blood depends mainly on the hematocrit and the rate of shearing. One may thus verify Casson's law (tau 1/2 = tauo 1/2 + S gamma 1/2) which represents approximately the rheological equation of normal blood and permits one to calculate a threshold for viscous outflow.