Danish anatomist and theologian who was a prodigy of his time. He went to grammar school at age three and lectured in Greek and Latin at age eleven. He became fascinated with anatomy and studied with Fabricius at Padua, where he wrote a manual on anatomy. His fame arose from his massive learning and reputation as a teacher. He first described the olfactory nerves and the suprarenal glands and published a textbook called De studio medico for his sons in 1628.