Meniscus
Historical document, translated for reference. It reflects medical knowledge of the 1920s–30s and is not medical advice.
Summary
This article defines the meniscus as the surface shape of a liquid within capillary tubes. It explains how the shape—concave or convex—is determined by the relationship between the forces of molecular cohesion and the forces of adhesion to the tube walls.
Encyclopedia entry (1928–1936)
MENISCUS, the shape of the surface of a liquid in capillary tubes. If the liquid wets the walls of the tube (e.g., water in a glass capillary), the meniscus is concave; for a non-wetting liquid (e.g., mercury in a glass capillary), the meniscus is convex. The specific shape of the meniscus depends on the ratio between the forces of molecular cohesion (M) and the forces of adhesion of the liquid to the wall (K). If K > M (the case of wetting), then the resultant of these two forces, R, is directed into the wall (see figure); the liquid rises up the capillary, and its surface has a concave shape, since at equilibrium the surface of the liquid is always perpendicular to the acting force.
If, however, K < M (non-wetting liquid), then the resultant R is directed into the liquid, and the meniscus has a convex shape.
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“Meniscus.” Soviet Medical Encyclopedia. English translation of Bolshaya Meditsinskaya Entsiklopediya, 1st ed. (Moscow, 1928–1936), ed. N. A. Semashko. https://sovietmedicalencyclopedia.com/article/meniscus/