He also noted that a thin film of oil behaves as a semipermeable membrane, precisely as predicted.[3] Based on these observations, Quincke asserted that the cell membrane comprised a fluid layer of fat less than 100 nm thick.[4] This theory was further extended by evidence from the study of anesthetics. Hans Horst Meyer and Ernest Overton independently noticed that the chemicals which act as general anesthetics are also those soluble in both water and oil. They interpreted this as meaning that to pass the cell membrane a molecule must be at least sparingly soluble in oil, their “lipoid theory of narcosis.”