An eminent German scientist, born at Potsdam, Brandenburg; was first an army doctor, and in 1849 became professor of Physiology in Königsberg, and subsequently in Bonn and Heidelberg; in 1871 he became professor of Physics in Berlin; was ennobled, and in 1887 nominated head of the Charlottenburg Institute; to physiology he made contributions of great value on the various sense-organs, and to physics on the conservation of energy; but his most original work was done in connection with acoustics in its relation to optics; his published works include "Theory of Sound Sensations'" and "Sensations of Tone as a Physiological Basis for the Theory of Music" (1821-1894).