Figure 3: Comparison of stereomicroscopic images of the lymph ducts into which Alcian blue and Trypan blue had been injected. (a) A primo vessel emerged in a lymph duct (double arrows) after a two-hour washing of the injected Alcian blue. This image corresponds to Figure 1(e). (b) The lymph duct after a two-hour washing of the injected Trypan blue became clear again without any hint of the presence of the primo vessel. This showed that the L-PVS was selectively stained by the Alcian blue, not by the Trypan blue. (c) Contrast-enhanced microscope image of a branched lymph duct (double arrows) that was extracted and put on a slide. Connective tissues wrapped the lymph duct. The stained L-PVS also branched.