MÜLLER, Johannes (1801–1858), one of the most distinguished physiologists of Germany, was born at Coblentz on 14th July 1801. He became a privat-docent in the university of Bonn in 1824. In 1826 he was appointed extraordinary professor of physiology in the same university, and he became the ordinary professor in 1830. In 1833 he was removed to the university of Berlin, where he filled the chair of anatomy and physiology with great distinction until his death on 28th April 1858. Müller made numerous researches in various departments of physiology, and in particular he extended knowledge as to the mechanism of voice and speech and of hearing, and as to the chemical and physical properties of lymph, chyle, and blood. It was, however, less as an original investigator than as a deep and far-seeing thinker that Müller made his mark on physiological science. From about 1740, when Haller flourished, numerous contributions to physiological science had been made by Whytt, Cullen, John Hunter, Spallanzani, Prochaska, Bichat, Charles Bell, Berzelius, Magendie, and others, but in 1830, when Müller may be said to have begun his labours, it was necessary to reduce these facts to order, to educe general principles, and to direct physiologists into new lines of research indicated by the brilliant discoveries made in physics and in chemistry since the beginning of the century. This Müller did, and he may therefore be regarded as the founder of modern physiology. The appearance of his Elements of Physiology between 1837 and 1840 (translated into English by Dr William Baly, and published in London in 1842) was the beginning of a new period. In this work Müller shows remarkable power both in marshalling facts and in philosophical reasoning. As a rule he not merely states and criticizes the labours of others but also contributes the results of his own observations. Whilst he is cautious in the acceptance of theories, he always places them before the reader in an original and suggestive light. The most important portion of the work is that dealing with nervous action and with the mechanism of the senses. Here he states the fruitful principle, not before recognized, that the kind of sensation following irritation of a sensory nerve does not depend on the mode of irritation but upon the nature of the sense-organ. Thus light, pressure, or mechanical irritation acting on the retina and optic nerve invariably produce luminous impressions. This is sometimes termed the law of specific nervous energy. As a teacher Müller exercised a powerful influence, and the great majority of the distinguished physiologists, such as Helmholtz, Du Bois Reymond, Ludwig, Volkmann, and Vierordt, who have made Germany famous in physiological science during the past thirty years, owe much to the germinating ideas of their great teacher.

Besides editing for many years a periodical entitled Archiv f. Anatomie, Physiologie, u. wissenschaftl. Mcdicin, to which he also contributed papers, he published the text-book on physiology above alluded to, and various important memoirs. For a list of these see Poggendorff, Biog.-Litter. Handwörterbuch, vol. ii.

Two men of the same name, Johannes Müller, have been celebrated in science: (1) John Müller (1699-1784), a professor of artillery and fortification at Woolwich, who wrote a mathematical treatise published in 1737; (2) Johannes Müller (born 1806), a writer on pharmacy and physiological chemistry, who published many memoirs from 1840 to 1850.