Vasomotion, tissue fluid flow and the formation of lymph.

Spontaneous vasomotor activity was studied in the sandwich window preparations of the subcutaneous fasciae of the dorsal skin of rats. Measurements of the periodic changes in diameter related to the length of the active vessel show that this phenomenon causes substantial periodic volumetric displacements in tissue. We propose the hypothesis that these volumetric displacements are partially made up by tissue displacement, and are partially due to displacement of the tissue fluid. The tissue fluid motion due to anteriolar vasomotion compared with the net tissue fluid motion due to fluid exchange from the corresponding number of capillaries, shows that these two effects are similar in magnitude. We propose the hypothesis that this periodic motion of fluid in the tissue constitutes an additional mechanism by which tissue fluid is propelled into the terminal lymphatics.