Figure 1.

Early studies of lymphatics. (A) The first illustrations of intraluminal (secondary) valves in lymphatics. (Left panel) Dog lymphatics drawn by Jan Swammerdam in June 1664 but only published in 1666 in a commentary on a contemporary textbook of anatomy. (Panel A reprinted from Table 24 in Blasius 1666 without restriction because figure is in the public domain.) (Right panel) Drawings by Frederik Ruysch published 1 year earlier (1665). The lymphatic labeled A has been dissected longitudinally to show the valves (labeled a). (Lymphatic labeled A, right side reprinted from Figure 1 in Ruysch 1665 without restriction because figure is in the public domain.) (B,C) Early drawings of the shape of lymphatic endothelial cells stained by silver nitrate. (B) Faint endothelial cell borders in lymphatics of guinea-pig diaphragm drawn in 1862. (Panel B reprinted from Table 2, Figure 2 in von Recklinghausen (1862) and reprinted without restriction because table and figure are in the public domain.) (C) Endothelial cells in lymphatic, where the cells are oak-leaf shaped, and in artery and vein of cat omentum drawn in 1918. The transverse lines over the artery and veins are outlines of smooth muscle cells. (Panel C is reprinted from Figure 1 in Casparis 1918 without restriction because figure is in the public domain.)