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 teachers was 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 shark and recognizing that the shark's teeth resembled certain unidentified fossils found from Tuscany (he concluded that the fossils were actually fossilized teeth). Steno went on to...