ESTIMATION OF RELATIVE VELOCITIES OF PLASMA AND RED CELLS IN THE CIRCULATION OF MAN

Abstract

To determine the relative velocities of the plasma and red cells a mixture of plasma dyed with T-1824 and red cells identified by means of selective agglutination techniques was injected instantaneously into the brachial artery of man. With the circulation to the hand occluded, serial collections of blood were taken from a large antecubital vein every 2 sec. On plotting the respective curves of concn. of the samples so obtained against time, it was detd. that the concn. of cells had reached its peak and was already declining when the concn. of dyed plasma was still rising. The greater mean velocity of the red cells is explained in terms of the established laws of hydraulics concerning laminar flow and Bernoulli''s principle of inverse proportionality between velocity and lateral pressure of fluid flowing in tubes. In addition, these results suggest the mechanism for the observations of previous investigators indicating a lower hematocrit in the capillaries as compared to the larger vessels.