Hermann von Helmholtz

German physiologist

• Born: August 31, 1821
• Birthplace: Potsdam, Prussia (now in Germany)
• Died: September 8, 1894
• Place of death: Charlottenburg, Berlin, Germany

Helmholtz contributed to the fields of energetics, physiological acoustics and optics, mathematics, hydrodynamics, and electrodynamics. His most important work was in establishing the principle of conservation of energy and in his experimental and theoretical studies of hearing and vision.

Early Life

Hermann Ludwig Ferdinand von Helmholtz (HEHLM-hohltz) was the eldest of four children of Ferdinand and Caroline Penne Helmholtz. His mother was a descendant of William Penn. His father studied philology and philosophy at the University of Berlin and was a teacher at the Potsdam gymnasium. He was a typical product of German Romanticism and Idealistic philosophy, with strong interests in music and art. These interests were passed on to his son, especially music, and became important aspects of his life and later work in physiological acoustics and optics.

Helmholtz was a sickly child, not entering the gymnasium until the age of nine, but he advanced rapidly and was encouraged by his father to memorize the works of Johann Wolfgang von Goethe, Friedrich Schiller, and the Greek poet Homer. His interest soon turned to physics. In 1837, he received a scholarship to study medicine at the Friedrich Wilhelm Institute in Berlin, with the provision that he would serve for eight years as an army surgeon after completing his degree.

While in Berlin, Helmholtz supplemented his medical studies with many science courses at the University of Berlin and studied mathematics on his own. In 1841, he began research under the great physiologist Johannes Peter Müller, who followed the German tradition of vitalism in explaining the unique characteristics of living organisms. Helmholtz joined the circle of Müller’s students, including Emil Du Bois-Reymond, Ernst Wilhelm von Brücke, and Carl Friedrich Wilhelm Ludwig, and they later became known as the Helmholtz school of physiology for their rejection of the nonphysical vital forces in favor of purely physical and chemical explanations of life processes.

Helmholtz completed his medical degree in 1842, with a dissertation showing that nerve fibers are connected to ganglion cells. After some further research on fermentation that seemed to support vitalism, he was appointed as army surgeon to the regiment at Potsdam. From that time on, he wrote at least one major paper every year except 1849, publishing more than two hundred articles and books before he died. In 1849, he was granted an early release from his military duty to accept an appointment as associate professor of physiology at Königsberg. Just before leaving Potsdam, he married Olga von Velten, the daughter of a physician, by whom he had two children.

Life’s Work

Helmholtz began to make major contributions to science even during his five-year tour of duty in the army, when he had little free time or access to laboratory facilities. Pursuing the ideas of the chemistJustus von Liebig, he made a quantitative study with homemade apparatus of the effects produced by muscle contraction and showed that it is accompanied by chemical changes and heat production. With this experimental evidence for transformation of energy (or force, as he called it), he undertook to establish the general principle that energy remains constant in all processes, whether animate or inanimate.

Arguing from the impossibility of perpetual motion with surprising mathematical sophistication, he demonstrated the principle of conservation of energy in its most general form and used it to refute vitalism. In 1847, “Über die Erhaltung der Kraft” (“On the Conservation of Force,” 1853) was presented to the Physical Society in Berlin. The importance of this discovery led to fierce controversy over scientific priorities, but Helmholtz willingly shared the credit. Julius Robert von Mayer’s prior announcement of this principle in 1842 was unknown to Helmholtz, whose work was much more detailed and comprehensive. James Prescott Joule is also given credit for this discovery for providing the first experimental verification.

After moving to his first academic post at Königsberg in 1849, Helmholtz began to try to measure the speed of nerve impulses, which Müller had considered too fast to be measured. This work led to the invention of the myograph for measuring short intervals from marks on a revolving drum. In 1851, he succeeded in measuring the speed along a frog’s nerve by stimulating it at increasing distances from the muscle and found it to be surprisingly slow at about 30 meters per second. About the same time, he invented the ophthalmoscope, which brought him world fame in the field of medicine. This invention made it possible for the first time to view the inside of the living human eye, opening up the field of ophthalmology.

In 1855, Helmholtz became a professor of anatomy and physiology at Bonn. Continuing his work on sensory physiology, he published the first of three volumes of his massive Handbuch der physiologischen Optik (1856; Treatise on Physiological Optics , 1924). He also wrote several papers on acoustics. His interest in acoustics led to his first paper on theoretical physics in 1858, creating the mathematical foundations of hydrodynamics by finding vortex solutions. At this time he accepted a position as professor of physiology at Heidelberg.

After moving to Heidelberg in 1858, Helmholtz established the new Physiological Institute. At Bonn, his wife’s health had started to deteriorate, and she died in 1859. During this stressful period, he achieved his greatest success in acoustical research, formulating his resonance theory of hearing, which explains the detection of differing pitches through variations of progressively smaller resonators in the spiral cochlea of the inner ear. He also published analyses of vibrations in open-ended pipes and of the motion of violin strings. In 1861, he wed Anna von Mohl, by whom he had three more children. In 1862, he completed the first edition of his highly influential treatise Die Lehre von den Tonempfindungen als physiologische Grundlage für die Theorie der Musik (1863; On the Sensations of Tone as a Physiological Basis for the Theory of Music , 1875).

During this time, Helmholtz also continued his optical research, amending Thomas Young’s theory of color vision to distinguish between spectral primaries and physiological primaries of greater saturation. The resulting Young-Helmholtz theory could then explain all color perception by proper mixtures of three physiological primaries and could be used to explain red color blindness as well. He incorporated these results in the second volume of Treatise on Physiological Optics and began work on the third volume, in which binocular vision and depth judgments were treated. This included a defense of empiricism against the nativist view that some aspects of perception are innate, leading to original work in non-Euclidean geometry. After the third volume was published in 1867, he believed that the field of physiology had grown beyond the scope of any one person, and he turned his attention almost exclusively to physics.

In 1871, Helmholtz accepted the prestigious chair of physics at Berlin after Gustav Robert Kirchhoff had turned it down. A new Physical Institute was established and he became the director, with his living quarters in the institute. He began his research in Berlin with a series of papers on electrodynamics, which brought James Clerk Maxwell’s electromagnetic field theory to the attention of continental physicists. In Germany, the interaction between electric charges was explained by Wilhelm Eduard Weber’s law of instantaneous action at a distance rather than action mediated by a field in an intervening ether. Helmholtz developed a more general action-at-a-distance theory but included Maxwell’s field theory as a limiting case, allowing for wave propagation at the speed of light. This work inspired his former student Heinrich Rudolph Hertz to do experiments leading to the discovery of radio waves in 1887.

Returning to his early interest in energetics, Helmholtz began to investigate energy processes in galvanic cells and in electrochemical reactions. This led him to the idea that electricity consists of discrete charges, or atoms of electricity, and that chemical forces are electrical in nature. Research in thermochemistry resulted in the concept of free energy that determines the direction of chemical reactions. An analysis of solar energy led to an estimate of 25 million years as the amount of time since the formation of the planets; this estimate was far too conservative, however, because of the ignorance of nuclear processes. During the late 1880’s, he formulated a theory for cloud formation and storm mechanics. One of his last great efforts was an unsuccessful attempt to derive all of mechanics, thermodynamics, and electrodynamics from Sir William Rowan Hamilton’s principle of least action.

Helmholtz was elected Reactor of the University of Berlin for one year in 1877. He was granted hereditary nobility by Emperor William I in 1882. Helmholtz became the first president of the new Physical-Technical Institute in 1888, freeing him from teaching so he could spend more time in research. For several years, he had suffered from migraines and fits of depression, which only long vacations seemed to cure. In 1893, he traveled to the United States as a delegate of the German government to the Electrical Congress at Chicago. On his return voyage, he fell down the ship’s stairs and injured his head. A year later, he suffered a cerebral hemorrhage, and, after two months of semiconsciousness, he died.

Significance

Hermann von Helmholtz was one of the leaders among German scientists who rebelled against the scientific romanticism of the first half of the nineteenth century. He successfully replaced vitalism with a rigorous physicochemical empiricism, but he also shared the goal of his predecessors in his desire to find unifying principles in nature. He succeeded in this goal with his elaboration of the principle of the conservation of energy. He demonstrated the interconnections among physiology, chemistry, medicine, and physics; he fell short, however, in his efforts to extend the principle of least action. Especially important were his three-color theory of vision, his resonance theory of hearing, and his invention of the ophthalmoscope.

Helmholtz also contributed to the transition of German universities from teaching academies to research institutions. The great laboratories he established at Heidelberg in physiology and at Berlin in physics placed Germany in the forefront of scientific research. Some of the most famous scientists at the end of the century had been his students, including Hertz, who discovered radio waves and the photoelectric effect; Max Planck, who introduced quantum theory; and the Americans Henry Augustus Rowland and Albert Abraham Michelson.

As a master and leader in biology, physics, and mathematics, he surpassed all others in the imposing theoretical and experimental treatises he produced, especially in sensory physiology. As perhaps the greatest scientist of the nineteenth century, he was the last scholar whose work embraced virtually all the sciences together with philosophy, mathematics, and the fine arts.

Bibliography

Boring, Edwin B. Sensation and Perception in the History of Experimental Psychology. East Norwalk, Conn.: Appleton-Century-Crofts, 1942. This volume, dedicated to Helmholtz, is a comprehensive history of sensory physiology and psychology. Describes the work of Helmholtz in physiological optics and acoustics, its historical background, and later developments from his ideas.

Cahan, David, ed. Hermann von Helmholtz and the Foundations of Nineteenth-Century Science. Berkeley: University of California Press, 1993. This 666-page book is a compilation of essays analyzing Helmholtz’s published and unpublished writings and describing his numerous contributions to science and philosophy. The essays are organized into three broad categories, discussing his work as a physiologist, a physicist, and a philosopher.

Elkana, Yehuda. The Discovery of the Conservation of Energy. Cambridge, Mass.: Harvard University Press, 1974. A history of the energy concept, including the physiological background and a chapter on the famous 1847 paper by Helmholtz on conservation of energy. Contains a bibliography and an appendix.

Helmholtz, Hermann von. On the Sensations of Tone as a Physiological Basis for the Theory of Music. Translated by Alexander Ellis. Mineola, N.Y.: Dover, 1954. An English translation of the fourth (and last) German edition (1877) of the great treatise on physiological acoustics. Includes a six-page introduction on the life of Helmholtz by Henry Margenau and a five-page bibliography of his major works with titles given in English translation.

‗‗‗‗‗‗‗. Science and Culture: Popular and Philosophical Essays. Edited by David Cahan. Chicago: University of Chicago Press, 1995. A collection of fifteen lectures that Helmholtz delivered between the 1850’s and the 1890’s. The topics of the lectures include the physiological causes of harmony in music, the conservation of force, the origins of the planetary system, and the theory of vision. Cahan’s introduction places the lectures in historical and scientific context.

Jungnickel, Christa, and Russell McCormmach. The Torch of Mathematics, 1800-1870. Vol. 1 in Intellectual Mastery of Nature: Theoretical Physics from Ohm to Einstein. Chicago: University of Chicago Press, 1986. The first volume of this two-volume work on German science describes some of Helmholtz’s physiological research. The second volume, The Now Mighty Theoretical Physics, 1870-1925, discusses his work in physics, especially in electrodynamics and energetics.

Königsberger, Leo. Hermann von Helmholtz. Translated by Frances Welby. Mineola, N.Y.: Dover, 1965. An abridged translation of the complete biography of Helmholtz in German published in 1906. The best source of information concerning his life and work, including discussions of his major publications.

Warren, Richard, and Roslyn Warren. Helmholtz on Perception: Its Physiology and Development. New York: John Wiley & Sons, 1968. Contains the English translations of six selections from lectures and articles by Helmholtz on sensory physiology. Includes a thirteen-page sketch of his life and work, a six-page evaluation of his work on sensory perceptions, and a five-page bibliography.