Hermann von Helmholtz

German physiologist and theoretical physicist (1821–1894)

Born in Potsdam, Germany, Helmholtz studied medicine at the Friedrich Wilhelm Institute in Berlin and obtained his MD in 1842. He returned to Potsdam to become an army surgeon, but returned to civilian life in 1848 and was appointed assistant at the Anatomical Museum in Berlin. He then held a succession of chairs at Königsberg (1849–55), Bonn (1855–58), Heidelberg (1858–71), and Berlin (1871–77) and later became director of the Physico-Technical Institute at Berlin Charlottenburg.

Helmholtz made major contributions to two areas of science: physiology and physics. In physiology he invented (1851) the ophthalmoscope for inspecting the interior of the eye and the ophthalmometer for measuring the eye's curvature. He investigated accommodation, color vision, and color blindness. His book Handbuch der physiologische Optik (Handbook of Physiological Optics) was published in 1867. Helmholtz also worked on hearing, showing how the cochlea in the inner ear resonates for different frequencies and analyzes complex sounds into harmonic components. In 1863 he published Die Lehre von den Tönemfindungen als physiologische Grundlage für die Theorie der Musik (The Sensation of Tone as a Physiological Basis for the Theory of Music). Another achievement was his measurement of the speed of nerve impulses (1850).

One of Helmholtz's interests had been muscle action and animal heat and this, inspired by his distaste for vitalism, led him to his best-known discovery – the law of conservation of energy. This was developed independently of the work of James Joule and Julius von Mayer and published as Über die Erhaltung der Kraft (1847; On the Conservation of Force). He showed that the total energy of a collection of interacting particles is constant, and later applied this idea to other systems.

Helmholtz also worked in thermodynamics, where he introduced the concept of free energy (energy available to perform work). In electrodynamics he attempted to produce a general unified theory. Heinrich Hertz, who discovered radio waves in 1888, was Helmholtz's pupil.

(b Potsdam, 31 Aug 1821; d Berlin, 8 Sept 1894). German scientist. After studying in Berlin he taught in Berlin, Königsberg, Bonn and Heidelberg. He contributed more to the musical aspect of acoustics than has any other individual. He analysed and explained the significance of overtones, explained combination tones and discovered summation tones; through his work on the ear he founded the present theory of hearing. He also worked on phase, wave patterns, beats and their role in consonance and dissonance, and temperament systems. Helmholtz devised a type of resonator for his experiments, built harmoniums and improved previous acoustical instruments. His classical work on acoustics (1863) was translated by A. J. Ellis as On the Sensations of Tone (1875). For Helmholtz's notation of pitches see Pitch notation.

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The German physicist and physiologist Hermann Ludwig Ferdinand von Helmholtz (1821-1894) made the first mathematical analysis of the principle of the conservation of energy and invented the ophthalmoscope. He also investigated the physics of tone and color perception.

Born on Aug. 31, 1821, in Potsdam, Hermann von Helmholtz was the eldest of six children of August Helmholtz, a teacher of philosophy and classics in the local gymnasium, and Caroline Penne Helmholtz, a descendant of the family which took prominent part in the founding of Pennsylvania. At the age of 17 he entered the Friedrich Wilhelm Institute as a scholarship student of medicine. Happily for science, Helmholtz had the genius to absorb medical and physiological training with the mind of a physicist. A great help in this respect was a teacher of his at the institute, Johannes Müller, the foremost German physiologist at that time, who insisted on carrying as far as possible the physical and chemical explanation in all problems of physiology. For Helmholtz this also meant the utmost use of mathematics, which he learned on his own to a very advanced degree by studying in his free time such mathematical classics as the works of Euler, Bernoulli, D'Alembert, and Lagrange. His doctoral dissertation (1842) described and analyzed the connections between nerve fibers and nerve cells, a discovery which he made by skillful use of the microscope and which forms the histological basis of the physiology and pathology of the nervous system.

Helmholtz's scholarship status implied the obligation to serve for 8 years as army doctor. His first post (1842-1843) was that of a house surgeon at the Charité Hospital in Berlin, followed by a stint of 5 years as assistant surgeon to the Royal Hussars at Potsdam. Despite time-consuming duties, Helmholtz found ways of developing his scientific interests. While at the Charité, he published a demonstration of the strictly chemical nature of fermentation and noted that a vitalistic account would be equivalent to assuming a perpetual-motion process. His papers on metabolism during muscular activity (1845) and on physiological and animal heat (1846, 1847) clearly indicated the great goal toward which his creative mind inevitably tended. In February 1847 he sent the first draft of the introduction of "The Conservation of Force" to Emil Du Bois-Reymond, who immediately declared that it was "an historical document of great scientific import for all time." The 26-year-old Helmholtz read the paper on July 23 before the Physical Society of Berlin. He was not the first to enunciate the idea that physical force (energy) was conserved in its various transformations, but his originality consisted in giving the principle a generalized mathematical form, which readily yielded expressions for kinetic and potential energy in mechanics, thermodynamics, electricity, and magnetism.

Academic World

The impact of the lecture and the availability of a teaching post in anatomy at the Academy of Arts in Berlin made it possible for Helmholtz to transfer to the academic world. In 1849 he accepted the invitation to serve as professor of physiology at the University of Königsberg, where he married Olga von Velten the same year. Among his first papers at Königsberg was "On the Method of Measuring Very Small Intervals of Time and Their Application to Physiological Purposes" (1851). The purpose was the determination of the rate of transmission of sense impressions along the nerves. The value he found shortly afterward was approximately 30 meters per second, in good agreement with subsequent determinations. The next year Helmholtz wrote of a marvelous new device to investigate the eye, the ophthalmoscope, which made its inventor world famous almost overnight.

In 1855 Helmholtz went to Bonn as professor of physiology and anatomy. During the following 3 years he started his incisive analysis of the mathematical relationships underlying tone perception and the esthetical judgment about various tonalities. At the same time he began publishing in a mature form his previous studies of the physiology of vision. The first volume of his famous Handbook of Physiological Optics appeared in 1856. The massive volume was a systematic application of physics to the phenomenon of vision. "On the Integrals of the Hydrodynamic Equations Which Express Vortex Motions" (1858) represented not only a brilliant solution of seemingly insoluble equations, but it also became the foundation for late-19th-century physicists who tried to devise a so-called vortex model of the ether.

Helmholtz spent the next 13 years at the University of Heidelberg. During his first year there his wife died. In 1861 Helmholtz married Anna von Mohl, who became mother of three children. He spent 13 years at Heidelberg, officially a physiologist but in reality a physicist.

The second part of Helmholtz's Handbook of Physiological Optics was published in 1862. The next year saw the publication of another systematic application of physics in physiology, Theory of the Sensations of Tone as Physiological Basis of the Theory of Music. In 1867 followed the third, and final, volume of the Handbook. Helmholtz's last 3 years at Heidelberg were marked by portentous investigations in theoretical physics. His interest was now in fluid mechanics, the foundations of geometry and electricity. Characteristically enough, when the chair of physics became vacant in Bonn, the university tried to get Helmholtz back as professor of physics. Helmholtz declined the opportunity, but in his reply he made no secret of his lifelong ambition: "Physics was really from the outset the science which principally attracted my interests. I was mainly led to medicine and thereby to physiology by the force of external circumstances. What I have accomplished in physiology rests mainly upon a physical foundation."

Life in Berlin

The same letter also gives a clue to the inspiration that animated Helmholtz during the last two major assignments of his life. The first of these was the professorship of physics at the University of Berlin (1871-1888). Following the Franco-Prussian war of 1870-1871, Berlin emerged as the capital of the First Reich, and as a professor of physics at the University of Berlin Helmholtz could be most influential in promoting the cause of scientific instruction in German schools and universities. There was much to be done if, in a predominantly humanistic and classical educational system, science courses were to gain a rightful place. It was the professorship of physics at the University of Berlin which he finally found most promising to reward him "for taking the new work of a new post" upon himself. His request was immediately granted that a chair in physics be complemented by an Institute of Physics reserved exclusively for advanced research. Shortly after his arrival in Berlin, Helmholtz gave evidence of the high level in physical research which he had in mind. His memoir read in 1872 before the Berlin Academy of Sciences, "On the Theory of Electrodynamics," represented a remarkable effort to provide a generalized form of electrodynamics, of which even James Clerk Maxwell's theory was but a particular case. In 1873 he was invited to lecture in the United States, but he felt that acceptance would hinder his researches at his institute, which had begun to attract the most promising young physicists in Germany. The foremost among them was Heinrich Hertz, who developed under Helmholtz's guidance the interest to test experimentally a chief consequence of Maxwell's theory, the propagation of electromagnetic oscillations in space. A high point in Helmholtz's own reflections on the problems of electricity was his Faraday lecture in 1881, in which he emphasized the essentially atomic structure of electricity, a contention fully confirmed a few years later by J. J. Thomson's work with cathode rays.

During this period Helmholtz began to achieve the status of a chief adviser to the state in scientific matters. He played a prominent part in the establishment of the Imperial Physico-Technical Institute (Physikalisch-Technische Reichsanstalt), of which he became the first director in 1888. Although a chief aim of the new institute was to carry out high-precision measurements, Helmholtz wanted the new institute to serve pure science as well as technology. During his last years acclaim and honors poured in from every side. His seventieth birthday became an occasion for nationwide celebrations. He died on Sept. 8, 1894, after months of struggle with paralysis. In no small measure, through his inspiration physics in Germany rose to unparalleled heights by the end of the 19th century, a position which remained unchallenged for another generation.

Further Reading

Leo Koenigsberger's classic three-volume biography is available in English in a one-volume abridgment by Frances A. Welby as Hermann von Helmholtz (1906). It covers equally well the personal and scientific aspects of Helmholtz's career and discusses his influence on science in the second half of the 19th century. A specialized study of Helmholtz is Richard M. Warren and Roslyn P. Warren, Helmholtz on Perception, Its Physiology and Development (1968). A detailed biographical account of Helmholtz's life is in Bessie Zaban Jones, ed., The Golden Age of Science: Thirty Portraits of the Giants of 19th-Century Science by Their Scientific Contemporaries (1966). Good discussions of Helmholtz are also in Henry Ernst Sigerist, The Great Doctors: A Biographical History of Medicine (1933), and Ralph Hermon Major, A History of Medicine (vol. 2, 1954).

For more information on Hermann Ludwig Ferdinand von Helmholtz, visit Britannica.com.

Helmholtz, Hermann (1821-94), German physiologist, physicist, and genius, one of the towering figures of 19th-century empirical science, including optics and human vision. In 1850, on the recommendation of Alexander von Humboldt, he became professor of physiology and pathology at Königsberg University, where he discovered a means of measuring the speed of nerve impulses and invented the ophthalmoscope. After holding posts in Bonn (1855) and Heidelberg (1858), and publishing his monumental Handbook of Physiological Optics (2 vols., 1856, 1867), he became professor of physics in Berlin (1871). There, in addition to research in many other fields, he investigated colour vision. In 1878 he became director of the Physikalische Institut, then first president (1888-94) of the new Physikalisch-Technische Reichsanstalt. Helmholtz's theories about human vision - whether or not properly understood - were a significant influence on the art photographers of the pictorialist era, from Emerson to Kühn.

— Jens Jaeger

Bibliography

• Cahan, D. (ed.), Hermann von Helmholtz and the Foundations of Nineteenth-Century Science (1994)

Helmholtz, Hermann von (1821-94) German scientist and philosopher. Helmholtz graduated from the Medical Institute in Berlin in 1843, and subsequently held appointments at Königsberg, Bonn, Heidelberg and Berlin. His physicalist leanings led him to disparage ‘vital forces’, then common in medicine, and to formulate the principle of conservation of energy. Work on hydrodynamics led to fundamental discoveries in topology, and he also studied the physiology of auditory perception. In physics, after an initial defence of the a priori status of Euclidean geometry, Helmholtz repudiated his Kantian heritage and followed the lead of Riemann and Lobachevsky. Helmholtz was the most influential German scientist of the Victorian period, and a leading figure in the conception of science as the search for fundamental laws.

(1821–94). German physiologist and physicist, born at Potsdam. He was the son of Ferdinand Helmholtz, a teacher of philology and philosophy in the gymnasium. His mother's maiden name was Penne; she was descended from the Quaker founder of Philadelphia, William Penn. Hermann Helmholtz became the founder of the science of perceptual physiology. He carried out a vast number of observational experiments, often with himself as observer, as well as physiological experiments for explanations. He also formulated psychological concepts which have lasting significance. His immense range — he was one of the greatest physicists of the 19th century — even includes ideas on aesthetics and art. He was also a director of research, and with his Popular Lectures a lucid presenter of science: by following a suggestion of his, his student Heinrich Hertz (1857–94) discovered how to confirm James Clerk Maxwell's theoretical prediction of radio waves. Helmholtz was professor of physiology at Königsberg (1849), Bonn (1855), and Heidelberg (1858). Then in 1871 he became professor of physics at Berlin, and from 1888 to 1894 was president of the Physikalisch-Technische Reichsanstalt, which he designed as 'an institute for the experimental promotion of exact science and the technique of precision'. It is, however, for his earlier work on the nervous system and especially on vision and hearing, and as the founder of the experimental study of perception, that he concerns us here.

His first great achievement, in 1850, was to measure the rate of conduction of signals in nerves. It had been thought that sensory signals arrive at the brain immediately. Indeed, the founder of modern physiology, Johannes Müller (1801–58) considered it to be beyond experimental possibility to measure the neural conduction rate, because nerves are so short, in comparison with the astronomical distances over which the velocity of light had been estimated, that no instrument could measure the very short time differences. But Helmholtz's friend Emil Du Bois-Reymond (1816–96), the originator of electrophysiology, suggested that there might be a molecular basis for neural conduction, so it could be a great deal slower than the velocity of light. Further, a new instrument, the chronograph, was invented in 1849, making it possible to record short durations and rapid changes with an electrically operated pen on a revolving drum. Helmholtz used this with frog preparations, and then on humans. The method with humans was to find the difference between reaction times to a stimulus at, say, the ankle and the calf of the leg. Since the muscle action time (which he also succeeded in measuring) would be the same in either case, a longer reaction time from the ankle must be due to conduction time in the nerve of the leg. Helmholtz found it to be comparable to the speed of sound, rather than of light. His father commented in a letter to him: 'the results at first appeared to me surprising, since I regard the idea and its bodily expression not as successive, but as simultaneous, a single living act, that only becomes bodily and mental on reflection; and I could as little reconcile myself to your view, as I could admit that a star that had disappeared in Abraham's time should still be visible.' This was, however, a misunderstanding which was for some time shared by the older physiologists, for as Helmholtz immediately pointed out to his father: 'the interaction of mental and physical processes is initiated in the brain, and consciousness, intellectual activity, has nothing to do with the transmission of the message from the skin, from the retina, or from the ear, to the brain. In relation to intelligence this transmission within the body is as external as the propagation of sound from the place at which it takes origin, to the ear.' The measurements did however lead Helmholtz to appreciate that the brain is quite slow, for reaction times are much longer than they should be from the speed of signals in peripheral nerves, and so he came to appreciate that a great deal of routeing and switching of signals must be going on during perception, and for decisions for muscle movement. This led to analogies between brain function and telephone exchange switching, and then computers.

Helmholtz was philosophically a thoroughgoing empiricist, believing that sensory signals only have significance as the result of associations built up by learning. We are essentially separate from the world of objects, and isolated from external physical events, except for neural signals which, somewhat like language, must be learned and read according to various assumptions, which may or may not be appropriate. This is the basis of Helmholtz's interest in perceptual and especially visual illusions. More generally, it is the basis also of his notion, at that time disturbing, that perceptions are 'unconscious inferences'. This challenged the prevailing view that responsibility, and just blame and praise, depend on consciously held reasons and motivations. Sigmund Freud's slightly later notion of an active unconscious mind is a rather different idea, though equally shocking to the Victorians. For Helmholtz it was simply that most of what goes on in the nervous system is not represented in consciousness. Physiological and psychological experiments are important, and often surprising in their findings, because we cannot experience or discover by introspection how we see or think, or even know on what data our perceptions and beliefs are based. Thus Helmholtz wrote of visual illusions, in his last paper on perception (1894):

• Knowledge gained through daily experience, with all its accidents, does not usually have the range and completeness which it is possible to obtain with experiments. ... We usually refer to incorrect inductive inferences concerning the meaning of our perceptions as illusions of the senses. For the most part they are the result of incomplete inductive inferences. Their occurrence is largely related to the fact that we tend to favour certain ways of using our sense organs — those ways which provide us with the most reliable and most consistent judgements about the forms, spatial relations, and properties of the objects we observe. ... Unusual perceptions, concerning whose meaning we have no trained knowledge, occur with unusual positions and movements of our sense organs, and incorrect interpretations of these perceptions may result. We can, in fact, lay down the general rule that with abnormal positions and movements of the eyes, the intuitions which occur are those of the objects which would naturally have to exist in order to produce the same perceptions under the conditions of normal vision.

Then, after pointing out that ordinary plane mirrors produce illusions of this kind, though we are seldom actually misled, he adds: 'most observers know how to change an unusual kind of observation into one that is common and normal, thus causing the illusion to be recognized and to disappear.' Thus after-images impressed on the retina by a flash of light are seen as external objects, even though we may realize they are illusory, as we move our eyes and find part of the visual world moving with them. The illusion persists but we are not fooled by it.

Helmholtz was remarkable in combining shrewd psychological accounts with extraordinarily powerful physical insights, as in his work on the conservation of energy. His experimental and inventive skills were also remarkable. They led to the ophthalmoscope (1851) for examining the retina; the ophthalmometer for measuring the curvature of the optical surface of the eye; and the Young–Helmholtz trichromatic theory of colour vision, which is the basis of current theories. In hearing, he introduced the resonance theory of pitch discrimination. That he achieved his results before there were stable sources of light, or electronic instruments for producing and measuring sound waves, humbles the present-day investigator.

Helmholtz's Treatise on Physiological Optics (3 vols., 1856–67; trans. 1924–5, reprinted 1962, 2000) is the foundation of the science of visual perception and well worth reading today by the serious student. His On the Sensations of Tone (1863; 4th edn. 1877, trans. 1954) was his main work on perception in hearing, and his Popular Lectures (1881; 1962) range from painting through perception to physics and the basis of geometry.

(Published 1987)

— Richard L. Gregory

Bibliography
• Kahl, R. (ed.) (1971). Selected Writings of Hermann von Helmholtz.
• Koenigsberger, L. (1906). Hermann von Helmholtz. The fullest and best biography, with a good account of the development of most of his ideas.
• McKendrick, J. G. (1899). Hermann von Helmholtz. More concerned with his work in physics than on perception or the mind.
• Wade, N. (2000). Helmholtz's Treatise on Physiological Optics (5th edn.). Trans. J. Southall.
• Warren, R. M., and Warren, R. P. (1968). Helmholtz on Perception: Its Physiology and Development. A selection of Helmholtz's writings on perception, with a short life and excellent comments on his work and ideas.

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