Steno, Nicolaus (nĭkəlāˈəs stēˈnō) [key], Latinized form of Niels Stensen nēls stānˈsən, 1638–86, Danish anatomist, geologist, and Roman Catholic prelate. He lived principally in Copenhagen, Paris, and Florence. He investigated the heart, brain, muscles, and glands and discovered (1661) the excretory duct (duct of Steno) of the parotid gland (one of the pairs of salivary glands). He pointed out the true origin of geological strata and of fossils and recorded his studies of crystallization. He was converted from Lutheranism to Roman Catholicism in 1667, became a priest in 1675, and vicar apostolic in N Europe in 1677. In his devotion to missionary work he virtually abandoned science. His Earliest Geological Treatise (1667) was translated and edited by Axel Garboe (1960).
See study by A. Cutler (2003).