Figure 4: Comparison of lymph ducts into which Alcian blue and toluidine blue had been injected. (a) Two branches of lymph ducts (one of them indicated with double arrows) and their L-PVS stained with Alcian blue. (b) Toluidine blue left stained spots in the lymph wall (arrow heads). It also leaked from the wall and stained the surrounding tissues. However, the L-PVS was not stained. (c) A thin blood vessel was deeply stained by using toluidine blue. How it flowed into the blood vessel is not known.