TY - JOUR T1 - <strong>Hermann von Helmholtz (1821–94)</strong> JF - Journal of Neurology, Neurosurgery &amp; Psychiatry JO - J Neurol Neurosurg Psychiatry SP - 766 LP - 766 DO - 10.1136/jnnp.65.5.766 VL - 65 IS - 5 AU - L F HAAS Y1 - 1998/11/01 UR - http://jnnp.bmj.com/content/65/5/766.abstract N2 - In the June 1998 issue of the Journal, this vignette was inadvertently published with the wrong stamp. It is reproduced here with the correct stamp.The physician Hermann von Helmholtz, born in Potsdam, was, on his mother’s side, a descendent of William Penn, founder of Pennsylvania. His contributions to science—which included physiology, optics, electrodynamics, and meteorology— were numerous.His doctoral thesis, begun in 1842, was on the connection between nerve fibres and nerve cells and he graduated from the Medical School in 1843. His demonstration in isolated preparations that muscles are the main source of animal heat, led him to his best known discovery, the law of conservation of energy and his paper in 1847Über die Erhaltung der Kraft … ER -