Johannes Muller (1801–1858) is frequently referred to as the father of experimental physiology. While it might be argued that the title belongs more properly to Sir Charles Bell, the fact remains that during the first half of the nineteenth century Muller was the dominant figure in the rapidly developing science of physiology. Through his own researches, particularly on reflex action and on human and animal vision, through his massive Handbuch der Physiologic des Menschen (1834–1840; a translation, Elements of Physiology, appeared 1840–1843), which became the standard reference work for physiologists throughout Europe, and through his pupils he made a lasting impression on the biological sciences; and the doctrine for which he became most famous, the law of specific energies of nerves, continues in modified form to present a challenge.
Müller, the son of a shoemaker, was born in Koblenz. In 1819 he matriculated at the University of Bonn, where he received his medical degree in 1822. After a year of further study in Berlin he was habilitated at Bonn in 1823. Until 1830 he was Privatdozent in anatomy and physiology, at which time he was granted a professorship. In 1833 he was called to the chair of anatomy and physiology at the University of Berlin, which he occupied until his death in 1858. During his career he became prominent in international scientific circles, was an active leader in university affairs (being elected Dehan in 1835 and Universitätsrektor in 1838), and during the political upheaval of 1848 he was head of the “fliegende Korps der Universitätsangehörigen.” Among his many pupils the best known are Ernst Brücke, Carl Ludwig, and Emil Du Bois-Reymond, the last of whom succeeded Muller in the Berlin chair. Even better known is Hermann von Helmholtz, who although not a pupil, was closely associated with Müller as a junior colleague and whose epoch-making contributions to sensory physiology are essentially extensions of Müller’s pioneering studies. It is a tribute to Müller’s greatness as a teacher that none of his pupils remained strictly faithful to their master’s doctrine. In the empiricist–nativist controversy, for instance, Müller was on the nativist side of the argument, and Helmholtz became the spokesman for the empiricists; Müller’s avowedly vitalist position was vigorously rejected by the younger generation of physiologists.
Müller’s stature as a scientist is most evident in the Handbuch, in which he summarized and evaluated the physiological knowledge of his day, reported much of his own research, and defined problems for further investigation. Although his bestknown contributions are in sensory physiology and what would now be called the experimental psychology of sensation and perception, he was interested in every aspect of human and animal physiology and even in the broader philosophical implications of natural science.
The famous law of specific energies was first formulated in the 1826 volume on the comparative physiology of vision, and it was amplified in Book 5 of the Handbuch. Briefly stated, it asserts that the basis of differentiation among sensory qualities is to be found not in the physical processes of the external world or in the receptors but in the condition of the sensory nerves. Our knowledge of the external world is thus an interpretation placed upon centrally aroused and immediately apprehended sensations. This is obviously not a totally new doctrine. The early British empiricist philosophers, notably George Berkeley, had made a similar distinction between sensation and interpretation, but without grounding it in anything more than a speculative physiology. A more direct anticipation is to be found in the independent discoveries by Charles Bell and François Magendie of the structural and functional differences between sensory and motor nerves, the sensory nerves being responsible for sensation and the motor nerves for muscular action. Müller extended the principle by according to each nerve its own unique sensory quality: color to the optic nerve, sound to the acoustic nerve, etc.; and a further refinement is to be found in Helmholtz’ hypothesis that an even more specific differentiation exists among the constituent fibers of a given nerve. One of the physiological implications of his principle, which Müller recognized but did not fully explore, is that the ultimate correlates of sensory quality are to be sought not in the nerves themselves but in the specialized structures of the cerebral cortex. Müller’s principle thus points towards a more generalized theory of cortical localization.
The Handbuch is a treatise on philosophy and psychology as well as on physiology. For Müller, both physiology and psychology are to be subsumed under a broader philosophy of nature. His philosophical views show the influence of the German metaphysical idealists, but he might be more properly classed as an Aristotelian in his conception of nature, and his approach to science was very close to that of Goethe. Purpose, he believed, is an observable fact of nature, without which the world of natural phenomena is unintelligible. Purpose is revealed in the forms of natural objects and events but emerges as conscious mind only with the differentiation of the specialized structures of the central nervous system, the brain being the special organ of consciousness. Causation in nature may be mechanical, chemical, or organic, the third of these involving a special life force (Lebenskraft) that is not reducible to the first two. A science which limits itself to the first two thus provides an incomplete account of nature. In Müller’s philosophy of nature, as in Goethe’s, the realm of natural law includes not only the mechanical processes of the physical world but also the phenomena of purposive striving, ideation, and reasoning. Miiller was a staunch exponent of the experimental method in science, but also like Goethe, he insisted that the data of unconstricted observation (unbefangene Beobachtung) are fully as legitimate as are those of the laboratory. In this respect he might be considered one of the forerunners of the phenomenological movement in experimental psychology.
Robert B. Macleod
[Directly related are the entriesNervous System, especially the article on Structure and Function OF the Brain; Senses. Other relevant material is found inPsychology, article on Physiological Psychology; and in the biographies of Bell; Helmholtz; Lashley. The section of the biography of Freudthat deals with the historical background of his thought is also relevant.]
1826 Zur vergleichenden Physiologic des Gesichtssinnes des Menschen und der Tiere, nebst einem Versuchüber die Bewegungen der Augen und über den menschlichen Blick. Leipzig: Cnobloch.
(1826) 1927 Über die phantastischen Gesichtserscheinungen. Leipzig: Barth.
(1834–1840) 1840–1843 Elements of Physiology. 2 vols. 2d ed. London: Taylor & Walton. → First published asHandbuch der Physiologic des Menschen.
BORING, EDWIN G. (1929) 1950 A History of Experimental Psychology. 2d ed. New York: Appleton.
Boring, Edwin G. 1942 Sensation and Perception in the History of Experimental Psychology. New York: Appleton.
Driesch, Hans (1905) 1922 Geschichte des Vitalismus. 2d ed., rev. & enl. Leipzig: Earth. → An expansion of the main parts ofDer Vitalismus als Geschichte und als Lehre, which was translated into English as The History and Theory of Vitalism and published in 1914 by Macmillan.
Haberling, Wilhelm 1924 Johannes Müller: Das Leben des rheinischen Naturforschers. Leipzig: Akademische Verlagsgesellschaft.
Roller, Gottfried 1958 Das Leben des Biologen Johannes Müllers, 1801–1858. Stuttgart: Wissenschaftliche Verlagsgesellschaft. mÜller, Martin 1927 Über die philosophischen Anschauungen des Naturforschers Johannes Müller. Leipzig: Barth.
Post, Karl 1905 Johannes Müller’s philosophische Anschauungen. Halle: Niemeyer.
Johannes Müller: see Regiomontanus.