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Hermann Von Helmholtz

energy ear conducted eye

1821-1894
German scientist who conducted breakthrough research on the nervous system.

Hermann Helmholtz was one of the few scientists to master two disciplines: medicine and physics. He conducted breakthrough research on the nervous system, as well as the functions of the eye and ear. In physics, he is recognized (along with two other scientists) as the author of the concept of conservation of energy.

Helmholtz was born into a poor but scholarly family; his father was an instructor of philosophy and literature at a gymnasium in his hometown of Potsdam, Germany. At home, his father taught him Latin, Greek, French, Italian, Hebrew, and Arabic, as well as the philosophical ideas of Immanuel Kant and J. G. Fichte (who was a friend of the family). With this background, Helmholtz entered school with a wide scope of knowledge. Though he expressed an interest in the sciences, his father could not afford to send him to a university; instead, he was persuaded to study medicine, an area that would provide him with government aid. In return, Helmholtz was expected to use his medical skills for the good of the government—particularly in army hospitals.

Helmholtz entered the Friedrich Wilhelm Institute in Berlin in 1898, receiving his M.D. four years later. Upon graduation he was immediately assigned to military duty, practicing as a surgeon for the Prussian army. After several years of active duty he was discharged, free to pursue a career in academia. In 1848 he secured a position as lecturer at the Berlin Academy of Arts. Just a year later he was offered a professorship at the University of Konigsberg, teaching physiology. Over the next 22 years he moved to the universities at Bonn and Heidelberg, and it was during this time that he conducted his major works in the field of medicine.

Helmholtz began to study the human eye, a task that was all the more difficult for the lack of precise medical equipment. In order to better understand the function of the eye he invented the ophthalmoscope, a device used to observe the retina. Invented in 1851, the ophthalmoscope—in a slightly modified form—is still used by modern eye specialists. Helmholtz also designed a device used to measure the curvature of the eye called an ophthalmometer. Using these devices he advanced the theory of three-color vision first proposed by Thomas Young. This theory, now called the Young-Helmholtz theory, helps ophthalmologists to understand the nature of color blindness and other afflictions.

Intrigued by the inner workings of the sense organs, Helmholtz went on to study the human ear. Being an expert pianist, he was particularly concerned with the way the ear distinguished pitch and tone. He suggested that the inner ear is structured in such a way as to cause resonations at certain frequencies. This allowed the ear to discern similar tones, overtones, and timbres, such as an identical note played by two different instruments.

Hermann von Helmhotz (The Library of Congress. Reproduced by permission.)

In 1852 Helmholtz conducted what was probably his most important work as a physician: the measurement of the speed of a nerve impulse. It had been assumed that such a measurement could never be obtained by science, since the speed was far too great for instruments to catch. Some physicians even used this as proof that living organisms were powered by an innate "vital force" rather than energy. Helmholtz disproved this by stimulating a frog's nerve first near a muscle and then farther away; when the stimulus was farther from the muscle, it contracted just a little slower. After a few simple calculations Helmholtz announced the impulse velocity within the nervous system to be about one-tenth the speed of sound.

After completing much of the work on sensory physiology that had interested him, Helmholtz found himself bored with medicine. In 1868 he decided to return to his first love—physical science. However, it was not until 1870 that he was offered the physics chair at the University of Berlin and only after it had been turned down by Gustav Kirchhoff. By that time, Helmholtz had already completed his groundbreaking research on energetics.

The concept of conservation of energy was introduced by Julius Mayer in 1842, but Helmholtz was unaware of Mayer's work. Helmholtz conducted his own research on energy, basing his theories upon his previous experience with muscles. It could be observed that animal heat was generated by muscle action, as well as chemical reactions within a working muscle. Helmholtz believed that this energy was derived from food and that food got its energy from the Sun. He proposed that energy could not be created spontaneously, nor could it vanish—it was either used or released as heat. This explanation was much clearer and more detailed than the one offered by Mayer, and Helmholtz is often considered the true originator of the concept of conservation of energy.

Helmholtz had been a sickly child; even throughout his adult life he was plagued by migraine headaches and dizzy spells. In 1894, shortly after a lecture tour of the United States, he fainted and fell, suffering a concussion. He never completely recovered, dying of complications several months later.

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