Niels Stensen Biography (1638-1686)

geologist, anatomist

Niels Stenson, also known as Nicalaus Steno, was born in Copenhagen on January 1, 1638, and died in Schwerin, northern Germany in 1686. The son of a well-to-do goldsmith, Steno studied first in Copenhagen, where one of his teacherswas the anatomist, Thomas Bartholin. In 1660, he began his travels and studies abroad; besides Copenhagen, he lived and studied in Paris, Amsterdam, Leyden, and Florence. While in Amsterdam, he discovered the parotid salivary duct(ductus Stenorzianus). After four years in Leyden, he returned to Copenhagen, but finding no post for him there, he went to Paris, where he made important observations on the anatomy of the brain. He arrived in Florence in 1665, where he became interested in geology after dissecting of the head of a sharkand recognizing that the shark's teeth resembled certain unidentified fossilsfound from Tuscany (he concluded that the fossils were actually fossilized teeth). Steno went on to publish his findings in his treatise of 1669, entitled De solido intra solidum, which made significant contributions to theincipient field of geology. In 1672, Steno returned to Copenhagen, where hegave anatomical demonstrations for a while. In 1674, he returned to Florence.In the last decade of his life Steno completely abandoned science and devoted himself exclusively to missionary work, residing in various towns of northern Germany until his death. As a cleric he is remembered primarily for his conversion from Lutheranism in 1667 to become a priest (1675), and later vicarapostolic (1677). An international group of geologists erected a bust over his tomb in 1883.

As a scientist, Steno is remembered for his discoveries in geology, particularly for his observations of fossils, geologic strata, and crystallization; and in human anatomy, for his studies of the heart, muscles, brain and glands.Steno showed that a pineal gland like that found in man is also found in other animals, and used this observation plus other arguments to refute Descartes' claim that the pineal gland is the seat of the soul and uniquely human. Hemade a distinction between the glands and the lymph nodes, which are not partof the glandular system anatomically. He also confirmed Malpighi's theorieson the incubation of the ovum in humans, and described the essential structure of the heart. He demonstrated that the long-held notion that tears arise inthe brain was wrong, and in 1661, discovered (in sheep) the excretory duct of the parotid gland (one of two identical salivary glands), which is now known as the duct of Steno. In the same year he investigated the glands of the eye, and in 1664 he made observations on muscles and glands that contributed torecognition of the muscular nature of the heart. In 1667, Steno treated thephysiology of muscles from a purely mechanical and mathematical point of view. His work with a microscope led him to describe the muscles as parallelepiped bundles of fascicles, subdivided into minute fibrils, with the tendon a tetragonal prism. He described contraction as a total response of a muscle to all of the tensile forces developed in each unit. His Paris discourse of 1669 argued that it is idle to speculate about the functions of the brain without knowing more about its structure.

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