These anatomical folds go by several different names, including the "valves of Kerckring", "Kerckring's folds", plicae circulares and valvulae conniventes. Kerckring used a microscope made by Spinoza.
These anatomical folds are also designated by several other names, including Kerckring's valves and circular folds. Kerckring employed a microscope built by Spinoza.