and isotonic contractile behaviour of the heart and it is this work that he is best known for. Frank's work on this topic preceded that of Ernest Starling, but both are usually credited with providing the foundations of what is termed the Frank–Starling law of the heart. This law states that "Within physiological limits, the force of contraction is directly proportional to the initial length of the muscle fiber". Frank also undertook important work into the physiological basis of the arterial pulse waveform and may have coined the term essential hypertension in 1911. His work on the Windkessel extended the original ideas of Stephen Hales and provided a sound mathematical framework for this approach. Frank also published on waves in the arterial system but his attempts to produce a theory that incorporated waves and the Windkessel are not considered to have been successful. Frank also did work on the oscillatory characteristics of the auditory apparatus of the ear and the thermodynamics of muscle. He also worked extensively on developing accurate methods to measure blood pressure and other physiological phenomena (e.g. Frank's capsule (Frank-Kapsel), optical Spiegelsphygmograph). Selected Published Work Zur Dynamik des Herzmuskels, Z Biol 32 (1895) 370 Die Grundform des arteriellen Pulses, Z Biol 37 (1899) 483-526 (a translation is given by Sagawa K, Lie RK, Schaefer J. J Mol Cell Cardiol 1990; 22: 253-277) Kritik der elastischen Manometer, 1903 Die Registrierung des Pulses durch einen Spiegelsphygmographen, Münchn Med Wschr 42 (1903) 1809–1810 Die Elastizitat der Blutgefasse. Zeitschrift fur Biologie, 1920; 71: 255-272. Die Theorie der Pulswellen. Zeitschrift fur Biologie, 1926; 85: 91-130. Schatzung des Schlagvolumens des menschlichen Herzens auf Grund der Wellen und Windkesseltheorie. Zeitschrift fur Biologie 1930; 90: 405-409. Publications about Otto Frank Otto Frank (Physiologe) Wikipedia (in German) Wilhelm Katner: Frank, Otto. In: Histor. Komm. b. d. Bayer. Akad. d. Wiss. (Hrsg.), Neue Deutsche Biographie, 5. Bd., Berlin 1961, S. 335–336 I. Fischer (Hrsg.): Biographisches Lexikon der hervorragenden Ärzte der letzten fünfzig Jahre. Berlin 1932, Bd. 1, S. 438 Kürschners Dtsch. Gelehrtenkalender 6 (1940/41) 378 A. P. Fishman, D. W. Richards (eds.): Circulation of the blood. New York 1964, pp. 110–113 A. Hahn: Nekrolog. Jahrb. d. bayer. Akad d. Wiss. 1944–1948, S. 202–205 K. E. Rothschuh: Geschichte der Physiologie. Berlin 1953, S. 184–186 K. Wezler: Otto Frank. Z Biol 1950; 103: 92–122 W. Blasius, J. Boylan, K. Kramer (Hrsg.): Begründer der experimentellen Physiologie. Munich 1971 H.G. Zimmer: