Lymphatic microcirculation in frog lung

Lymphatic microvessels were microscopically observed on the surface of frog lungs. Magnified images of lymphatic microvessels were recorded on video tapes. The lymphatic microcirculation was studied on a TV monitor at the magnification of 1500 times. 1) valves were observed in lymphatic microvessels, whose diameter was 15 micron, in frog lungs, 2) the valves were incompetent, 3) contained particles repeatedly flowed backwards and forwards in each lymphatic section, 4) after repetition of the movements, particles passed through the outlet valve, 5) particles seldom flowed back through the inlet valve into the preceding section of the lymphatic, 6) the peak flow velocity of particles attained 0.5 mm/sec, and 7) the mean flow velocity was 11 +/- 4 micron on an average and +/- SD, 8) the diameter of a localized portion of the lymphatic microvessels changed periodically.