Flow conditions of red cells and plasma in microvascular bifurcations.

The flow conditions of red cells and plasma in microvascular ramifications were investigated in a biological model of the frog's retrolingual membrane. Upon the controllable reduction of blood flow from the arterioles into the microvascular bed, with an appropriate decrease of red cell: plasma ratio in the blood, a tendency of the red cells to be drawn along the parent main capillaries without entering the branching capillaries was in evidence. These latter thus transformed into the plasmatic capillaries deprived of red cells. The factors being responsible for this process were found to be as follows: (a) the diameter of branching capillaries, (b) the angles of off-shoots, (c) the degree of slow-down of blood flow velocity in the branches, and (d) the reduction of red cell: plasma ratio in parent vessels. The direct relationship was found between these factors and the transformations of the off-shoots into the plasmatic capillaries.