# Hermann von Helmholtz

Hermann von Helmholtz

Hermann Ludwig Ferdinand Helmholtz , from 1883 by Helmholtz , (born August 31, 1821 in Potsdam , † September 8, 1894 in Charlottenburg near Berlin ) was a German physiologist and physicist . As a universal scholar , he made important contributions to optics , acoustics , electrodynamics , thermodynamics and hydrodynamics . He was one of the most influential naturalists of his time and was alluding toOtto von Bismarck also referred to as the " Reich Chancellor of Physics ".

## Life

Hermann Helmholtz one year after the publication of his article on the conservation of force (1848)
Memorial plaque on the former Physikalisch-Technische Reichsanstalt, in Berlin-Charlottenburg
Interview of the Helmholtz biographer David Cahan in the resonator - Podcast

Hermann Helmholtz was the son of August Ferdinand Julius Helmholtz and Caroline Penne (1797-1854). Throughout his life he had a close relationship with his younger brother Otto , who became an engineer.

He attended the " Große Stadtschule " grammar school in Potsdam, where his father worked as director and from whom he had already been taught philosophy , old and new languages.

### Studies and activities in Berlin and Potsdam

Even seventeen-year-old Helmholtz was very interested in physics. The natural sciences , especially physics, were, however, regarded as subjects of the artless arts. Therefore, from 1838 Helmholtz studied medicine at the medical-surgical Friedrich Wilhelm Institute in Berlin, where he was a student of the physiologist Johannes Müller , among other things . Helmholtz was in 1842 with a thesis in microscopic anatomy doctorate . He was an above-average graduate, but initially there was little evidence of an academic career. He initially worked for a year as a junior physician at the Charité .

From 1843, Helmholtz served in Potsdam , since studying at the institute he had chosen included the obligation to do eight years of military service. In 1846 he became a military doctor in the royal regiment. In 1848 he was prematurely discharged from military service on the recommendation of Alexander von Humboldt and taught anatomy at the Berlin Art Academy.

### Professorships for physiology in Berlin, Königsberg, Bonn and Heidelberg

In 1848 Helmholtz accepted a professorship for physiology in Berlin, succeeding Ernst Wilhelm von Brücke . He was focused on his work and cared less about the political processes ( 1848 Revolution ) - unlike his colleague Emil Heinrich Du Bois-Reymond, for example . On August 26, 1849, he married Olga von Velten (1827-1859).

Anna Helmholtz (1869)
Hermann Helmholtz portrayed
by Ludwig Knaus in 1881

In 1849 he was appointed professor of physiology and pathology in Königsberg . However, his wife, suffering from tuberculosis, could not stand the harsh climate in East Prussia . With the mediation of Alexander von Humboldt, Helmholtz moved to Bonn in 1855 to accept the vacant chair for physiology. There he lived in the Villa Vinea Domini . In 1858 Helmholtz accepted a well-paid professorship in Heidelberg, where he was the first holder of a physiology chair at the University of Heidelberg until 1870. Wilhelm Wundt was his assistant there from 1858 to 1863 . In 1858 Hermann von Helmholtz was elected a corresponding member and in 1870 a foreign member of the Bavarian Academy of Sciences .

In December 1859 his wife Olga died, leaving him with two young children. On May 16, 1861, Helmholtz married his second wife, Anna von Mohl (1834–1899). Both marriages resulted in a total of five children (three sons and two daughters). A son from his first marriage was the railway designer Richard von Helmholtz (1852–1934). A daughter from the second marriage was Ellen von Siemens-Helmholtz (1864-1941), the wife of the industrialist Arnold von Siemens (her father-in-law was Werner von Siemens ).

Helmholtz belonged to various other academies and learned societies at home and abroad, including the Royal Society of Edinburgh (since 1864), the Royal Swedish Academy of Sciences (since 1866) and the Royal Physiographical Society in Lund and the American Academy of Arts and Sciences (both since 1868), the American Philosophical Society (since 1873), and the National Academy of Sciences (since 1883).

### Professorship for physics in Berlin

In 1870, the professor of physics at the Friedrich-Wilhelms-Universität Berlin , Heinrich Gustav Magnus, died . Helmholtz was offered this professorship. Since he had dealt more with physics than physiology in recent years, he accepted the offer. Even then, Helmholtz was considered one of the greatest, most versatile thinkers and researchers in Germany. With great effort, he was adopted by the educated population of Heidelberg.

In 1870 Helmholtz was appointed a member of the Prussian Academy of Sciences . He also became a member of the Royal Swedish Academy of Music (1870) and the Royal Society of Sciences in Uppsala (1872).

In 1877/1878 he was the rector of the university. From 1879 to 1883 the young Heinrich Hertz worked for Helmholtz in Berlin. In 1883 Helmholtz was raised to the nobility. From 1882 he was, alongside Wilhelm Foerster and Werner von Siemens , one of the initiators for the later establishment of the Physikalisch-Technische Reichsanstalt . The many innovations in electrical engineering, the measurement of electricity quantities, required uniform standardization. In 1888 Hermann von Helmholtz became the first president of the Physikalisch-Technische Reichsanstalt in Charlottenburg.

Many strokes of fate darkened the life of Helmholtz in the last phase: the death of his son Robert (1889) and the death of his friend Werner von Siemens (1892). In 1894 his student Heinrich Hertz and his colleague August Kundt died .

On September 8, 1894, Helmholtz died of a second stroke. He found his final resting place in Dept. AT-52 at the Wannsee cemetery, Lindenstrasse . The design of the tomb was made by the sculptor Adolf von Hildebrand . His grave has been dedicated to the city of Berlin as an honor grave since 1967 .

### family

Helmholtz was married twice. In 1849, Hermann von Helmholtz and the doctor's daughter Olga von Velten (1827-1859) married in Berlin-Dahlem . The couple had two children:

• Richard (1852-1934)
• Katharina (1850–1878) ⚭ 1872 with Freiherr Wilhelm von Branca (* September 9, 1844; † March 12, 1928)

After the death of his first wife, he married Anna von Mohl (1834–1899), a daughter of the political scientist Robert von Mohl († 1875), in Heidelberg in 1861 . The couple had two sons and a daughter:

• Robert (1862-1889)
• Ellen (1864–1941) ⚭ 1884 with Arnold von Siemens (1853–1918)
• Friedrich Julius (1868-1901).

## research

Helmholtz was an extraordinarily versatile scientist who was also interested in the interrelationships between physics, physiology, psychology and aesthetics. The following structure is therefore only to be understood as a guide.

For example, at the beginning of his scientific work, Helmholtz came through physiological studies of fermentation , putrefaction and the heat production of living beings (which he attributed mainly to muscle work) to the formulation of the law of conservation of energy , i.e. an elementary law of physics. In Heidelberg, from 1858, Helmholtz dealt with the medical fundamentals of optical and acoustic physiology - and at the same time with questions of theoretical physics ( hydrodynamics and electrodynamics ) and with mathematical questions (geometry).

### physiology

German special postage stamp 1994 with Helmholtz portrait, human eye and color triangle

As early as 1842, Helmholtz demonstrated the origin of nerve fibers from ganglion cells in his doctoral thesis . In 1846, during his time as a military doctor, Helmholtz set up a laboratory in Potsdam and wrote an experimental work on metabolic consumption during muscle actions .

From 1849 Helmholtz, as professor of physiology and pathology in Königsberg, devoted himself intensively to the sensory organs of the eye and ear. Here he developed the ophthalmoscope for viewing the fundus of the eye from cemented together "glasses and cover glasses for microscopic purposes " . Helmholtz also developed an apparatus for measuring the nerve conduction velocity in frogs, the myograph .

“I have found that a measurable time elapses while the stimulus that a momentary electrical current exerts on a frog's hip plexus propagates to the point where the thigh nerve enters the calf muscle. For large frogs whose nerves were 50 to 60 millimeters long, and which I had kept at 2 to 6 degrees Celsius, while the temperature of the observation room was between 11 and 15 degrees, this period was 0.0014 to 0.0020 of a second. "

- Hermann Helmholtz : in January 1850
Memorial plaque at the Beethoven-Gymnasium Bonn for Helmholtz's professorship for anatomy and physiology in Bonn (1855-1858)

Helmholtz helped Thomas Young 's additive theory of color vision to breakthrough in 1852 , showing that three basic colors are sufficient to produce all others. He suggested that there must therefore be three types of photoreceptor cells in the eye ( three-color theory ). In 1851 he invented the ophthalmometer for determining the radii of curvature of the cornea and in 1857 the telestereoscope .

He developed a mathematical theory to explain timbre through overtones , the resonance theory of hearing and based on it, the theory of tone sensations as the physiological basis for the theory of music (1863).

In epistemological discussions, Helmholtz dealt with problems of counting and measuring as well as the general validity of the principle of the smallest effect . On the basis of his optical and acoustic investigations, he modified the classical concept of perception , rejected the existence of fixed forms of perception , in contrast to Kant , and therefore considered it possible to make non-Euclidean geometries clear. The four-phase model of the creative process is based on observations made by Helmholtz.

In the last volume of his work Handbuch der Physiologische Optik , published 1856–1867 , he presented the role that the unconscious conclusion plays in perception.

### physics

Hermann von Helmholtz
( heliogravure from 1894)

From October 1845 Helmholtz came into contact with the physics professor Heinrich Gustav Magnus . At that time, the physicists group under Magnus included Ernst Wilhelm Brücke (medic), Emil Du Bois-Reymond (medic), Werner von Siemens (lieutenant in the artillery), and Johann Georg Halske (mechanic). In 1845 the group founded the Physikalische Gesellschaft zu Berlin and a magazine entitled “Advances in Physics”.

In his treatise On the Conservation of Force (1847) he formulated the law of conservation of energy in more detail than Julius Robert von Mayer had done in 1842, and thus contributed significantly to the recognition of this initially very controversial principle. He fended off allegations of plagiarism by many of his contemporaries by saying that he was unfamiliar with Mayer's work, which had appeared five years earlier. By applying the law of conservation of energy to living beings, Helmholtz contradicted the vitalists , who assumed a vital force as the basic force of life.

With the compilation of the vortex theorems (1858 and 1868) on the behavior and movement of vortices in frictionless fluids , Helmholtz provided important principles of hydrodynamics . In investigations into electrodynamics , Helmholtz sought a compromise between the theories of Franz Ernst Neumann and James Clerk Maxwell . Mathematically elaborated studies of natural phenomena such as cyclones , thunderstorms or glaciers made Helmholtz the founder of scientific meteorology .

The three essays on the “Thermodynamics of Chemical Processes” (1882/1883) are among the most outstanding later achievements of Helmholtz. Here Helmholtz applied the main principles of thermodynamics to electrochemistry . He introduced the concept of free energy , which can be used to predict whether a chemical reaction according to the laws of thermodynamics ( Gibbs-Helmholtz equation ) is possible.

Helmholtz statue in front of the Humboldt University in Berlin on a base made of Marx green marble

### Helmholtz coil

Main article: Helmholtz coil

The Helmholtz coil is a frequently used, simple geometry for generating an almost homogeneous magnetic field that is accessible from all sides . The arrangement consists of two coaxially at a distance equal to that of their radius opposite ring coils with the same number of turns.

If current flows through the individual coils in the same direction, a large area with constant field strength is obtained. If the coils are traversed in opposite directions, a largely constant field gradient is obtained in the inner area.

### Helmholtz resonator

Main article: Helmholtz resonator

An acoustic resonator used for sound analysis (a vibratory system that begins to vibrate when excited at the natural frequency ) consists of an air-filled hollow sphere with an opening. The Helmholtz resonator is used in many ways today, e.g. B. in resonance charging in car engines to increase performance and reduce consumption.

### Helmholtz differential equation

Main article: Helmholtz differential equation

The general partial differential equation is called the Helmholtz equation

${\ displaystyle \ Delta \ varphi + k ^ {2} \ varphi = 0}$

designated. is the Laplace operator . ${\ displaystyle \ Delta}$

In electrodynamics, the Helmholtz equation results from the wave equation for the vector potential in Lorenz calibration in Fourier space :

${\ displaystyle \ Delta {\ vec {A}} + \ omega ^ {2} \ mu \ epsilon {\ vec {A}} = \ Delta {\ vec {A}} + {\ frac {\ omega ^ {2 }} {c ^ {2}}} {\ vec {A}} = 0}$

### Overlay principle according to Helmholtz

If there are only linear resistances and independent sources (current sources and / or voltage sources) in a network, the following relationship applies:

“The effect (current or voltage) at any point in the network, which is caused by all sources, is equal to the sum of the effects of each individual source, if at the same time the remaining sources are replaced by their ideal internal resistances. Ideal voltage sources are therefore to be short-circuited, ideal current sources are to be replaced by an open circuit. "

The Helmholtz superposition principle only applies to currents and voltages, not to power.

## Helmholtz as namesake

Honorary grave in the Wannsee cemetery, Lindenstrasse

The following are named after Hermann von Helmholtz:

In 1969 the proposal was made to name the physical unit for the electrical double-layer moment Helmholtz .

In 1939, the Nazi Association of German Technology, with the consent of Reich Post Minister Wilhelm Ohnesorge and Reich Minister of Transport Julius Dorpmüller, proposed to Adolf Hitler to use the term Helmholtz instead of Hertz for the unit of frequency , while retaining the abbreviation Hz . The background was the Jewish descent of Heinrich Hertz , whose teacher was Helmholtz. The proposal was not carried out.

The designation of musical tone symbols with commas in front of or apostrophes after the letters (e.g. a dashed  a or a ' for the concert pitch ) is also called the Helmholtz spelling.

## exhibition

The Adolf Würth Center for the History of Psychology in Würzburg showed between December 2012 and May 2015 an exhibition on Hermann von Helmholtz - a pioneer in psychology .

## Fonts

• About maintaining strength. Reimer, Berlin 1847. ( digitized and full text in the German text archive )
• About the interaction of the forces of nature and the related latest research in physics: a popular scientific lecture, held on February 7th, 1854. Graefe & Unzer, Königsberg 1854. (at the HU Berlin: full text )
• On the accommodation of the eye. In: Graefes Archive for Ophthalmology. Volume 1, 1854-1855, pp. 1-74.
• Theory of air vibrations in tubes with open ends. In: Journal for pure and applied mathematics. 57, No. 1, 1860, pp. 1-72. ( Digitized and full text in the German text archive )
• The doctrine of the sensations of sound as a physiological basis for the theory of music . Friedrich Vieweg & Sohn, Braunschweig 1863 ( online ), reprint: Minerva-Verlag, Frankfurt am Main 1981, ISBN 3-8102-0715-2 . Second edition: Friedrich Vieweg & Sohn, Braunschweig 1865, Textarchiv - Internet Archive . Excerpts from the 1896 edition .
• On the Academic Freedom of the German Universities - Speech given at the beginning of the rectorate at the Friedrich-Wilhelms-Universität zu Berlin on October 15, 1877. August Hirschwald, Berlin 1878. (at the HU Berlin: full text )
• The mechanics of the ossicles and the eardrum. In: Pflüger's archive of the entire physiology. Volume 1, 1868, pp. 1–60, Textarchiv - Internet Archive (also from Max Cohen and Son, Bonn 1869)
• Epistemology writings. Commented by Moritz Schlick and Paul Hertz , ed. from the corner of Bonk . Springer, Vienna / New York 1998, ISBN 3-211-82770-6 .
• Dynamics of continuously spread masses . Edited by Otto Krigar-Menzel. Verlag JA Barth, Leipzig 1902, Textarchiv - Internet Archive .
• About maintaining strength. (1847) / About vortex movements. (1858), ed. by A. Wangerin, 2nd edition. (Reprint of the edition Leipzig, Engelmann, Thun: German, Frankfurt am Main 1996, ISBN 3-8171-3001-5 )
• Two hydrodynamic papers by H. v. Helmholtz. I. About vortex movements (1858) II. About discontinuous fluid movements (1868) Edited by A. Wangerin. Verlag Wilhelm Engelman, Leipzig 1896, Textarchiv - Internet Archive
• On the history of the principle of the smallest action. Meeting reports of the Royal Prussian Academy of Sciences in Berlin 14, 1887 (at the HU Berlin: full text )
• Treatises on philosophy and geometry , ed. And included. by Sabine S. Gehlhaar. Junghans, Cuxhaven 1987, ISBN 3-926848-00-6 .
• Lectures on the theory of heat . Edited by Franz Richarz. Verlag JA Barth, Leipzig 1903, Textarchiv - Internet Archive
• Description of an ophthalmoscope for examining the retina in the living eye. Unchangeable Reprint d. Ed. Leipzig, JA Barth, 1910, Leipzig 1968.
• Physiological optics . Vol. 3. (JPC Southall, Trans.) Optical Society of America, Rochester NY 1925/1909.
• Thinking in science . Unchangeable reprograph. Nachdr. Wissenschaftliche Buchgesellschaft, Darmstadt 1968.
• The facts in perception / counting and measuring viewed epistemologically . Unchangeable photomechan. Nachdr. Wissenschaftl. Book Society, Darmstadt 1959.
• Lectures and speeches by Hermann von Helmholtz . First volume. Fourth edition. Verlag Friedrich Vieweg & Sohn, Braunschweig 1896, Textarchiv - Internet Archive .
• Lectures and speeches . Volume 2. 4th edition. Vieweg, Braunschweig 1896.
• Manual of Physiological Optics . L. Voss, Leipzig 1867.
• Lectures on the electromagnetic theory of light. Hamburg, Leipzig 1897.
• Philosophical and popular science writings. Edited by Michael Heidelberger, Helmut Pulte and Gregor Schiemann. 3 volumes. Felix Meiner Verlag, Hamburg 2017, ISBN 978-3-7873-2896-3 .

## literature

• NN: Hermann von Helmholtz. Dedicated by one of his students on the occasion of his 70th birthday. , in: The gazebo. Illustrated family magazine. Year 1891, pp. 593-595. With a portrait as a wood engraving, after a photograph by Fritz Leyde & Co., Berlin.
• David Cahan (Ed.): Hermann von Helmholtz and the Foundations of Nineteenth-Century Science (= California studies in the history of science. Volume 12). University of California Press, Berkeley / Los Angeles / London 1994, ISBN 0-520-08334-2 .
• Wolfgang U. Eckart , Christoph Gradmann : Hermann Helmholtz and science in the 19th century. In: Spectrum of Science . December 1994, p. 100 ff. ( Online )
• Walther GerlachHelmholtz, Hermann Ludwig Ferdinand von. In: New German Biography (NDB). Volume 8, Duncker & Humblot, Berlin 1969, ISBN 3-428-00189-3 , pp. 498-501 ( digitized version ).
• Erwin Hiebert: The Helmholtz Legacy in Physiological Acoustics Springer, 2014.
• Herbert Hörz : About the epistemology of Helmholtz. In: Structure. Volume 13 (1957), H. 10, pp. 423-432. Digitized
• Herbert Hörz: Physiology and culture in the second half of the 19th century. Letters to Hermann von Helmholtz. Basilisken-Presse, Marburg 1994, ISBN 3-925347-30-5 . Digitized
• Herbert Hörz: Building bridges between two cultures. Helmholtz in correspondence with humanities scholars and artists. Basilisken-Presse, Marburg 1997, ISBN 3-925347-44-5 . Digitized
• Herbert Hörz: Natural Philosophy as a Heuristic? Correspondence between Hermann von Helmholtz and Lord Kelvin (William Thomson). Basilisken-Presse, Marburg 2000, ISBN 3-925347-56-9 . Digitized
• Leo Koenigsberger : Hermann von Helmholtz. 3 volumes. Olms, Braunschweig 1902. (Reprint: Olms-Weidmann, Hildesheim 2003, ISBN 3-487-11902-1 )
• Königsberger: Hermann von Helmholtz . Second volume. Verlag F. Vieweg and Son, Braunschweig 1903, Textarchiv - Internet Archive
• Lorenz Krüger (Ed.): Universal genius Helmholtz. Looking back after 100 years. Academy, Berlin 1994, ISBN 3-05-002667-7 .
• Theodor Leiber: From the mechanistic world view to the self-organization of life: Helmholtz 'and Boltzmann's research programs and their significance for physics, chemistry, biology and philosophy (= Alber series of theses. Volume 6). Alber, Freiburg im Breisgau and others 2000, ISBN 3-495-47979-1 .
• Adolph PaalzowHelmholtz, Hermann von . In: Allgemeine Deutsche Biographie (ADB). Volume 51, Duncker & Humblot, Leipzig 1906, pp. 461-472.
• Helmut Rechenberg : Hermann von Helmholtz. Pictures of his life and work. Wiley, Weinheim 1994, ISBN 3-527-29276-4 .
• Julius Reiner: Hermann von Helmholtz. Theodor Thomas publishing house, Leipzig 1905.
• Matthias Rieger: Helmholtz Musicus. The objectification of music in the 19th century through Helmholtz's theory of sound sensations. Scientific Book Society, Darmstadt 2006, ISBN 3-534-19200-1 . ( Abstract ).
• Karl E. Rothschuh : Hermann von Helmholtz. In: Hans Schadewaldt (Ed.): The famous doctors. [2. or German, much expanded edition based on René Dumesnil: Médecins célèbres, Paris] Cologne without year [between 1964 and 1973], pp. 280–282.
• Gregor Schiemann : Loss of certainty of truth. Hermann von Helmholtz's Mechanism in the Dawn of Modernity. A study on the transition from classical to modern natural philosophy. Scientific Book Society, Darmstadt 1997, ISBN 3-534-13265-3 .
• Johannes Steudel : Hermann von Helmholtz. In: Rudolf Creutz, Johannes Steudel (ed.): Introduction to the history of medicine in individual presentations. Iserlohn 1948, pp. 297-320.
• Armin Stock, Jost Lemmerich : Hermann von Helmholtz: A trailblazer in scientific psychology. Adolf Würth Center for the History of Psychology at the University of Würzburg, Würzburg 2014, ISBN 978-3-00-044640-5 .
• Dieter Ullmann: Ohm-Seebeck-Helmholtz and the tone color problem. In: NTM series for the history of the natural sciences, technology and medicine . Volume 25, H. 1, 1988, pp. 65-68.
• Contributions to the psychology and physiology of the sense organs. Hermann von Helmholtz as a festive greeting on his seventieth birthday . Presented by Th. W. Engelmann, E. Javal, A. König, J. von Kries, Th. Lipps, I. Matthiessen, W. Preyer, W. Uthoff. Collected and edited by Arthur König. Verlag von Leopold Voss, Hamburg / Leipzig 1891, Textarchiv - Internet Archive
• Emil Warburg , Max Rubner , Moritz Schlick : Helmholtz as a physicist, physiologist and philosopher: three lectures held to celebrate his 100th birthday. Müller Hofbuchhandlung, Karlsruhe 1922.
• Franz Werner: Hermann von Helmholtz: Physiologist and physicist, regimental doctor and regent of science. 1821-1894. In: Rainer Brüning, Regina Keyler: Life pictures from Baden-Württemberg. Volume 24. Edited on behalf of the Commission for Historical Regional Studies in Baden-Württemberg. Kohlhammer, Stuttgart 2013, pp. 234–266.
• Franz Werner, The appointment of Hermann von Helmholtz to the University of Heidelberg , in: Wolfgang U. Eckart, Klaus Volkert (Hrsg.): Hermann von Helmholtz. Lectures at a Heidelberg symposium on the occasion of the hundredth anniversary of death. Centaurus, Pfaffenweiler 1996, pp. 63-96
• Franz Werner, Hermann Helmholtz 'Heidelberger Jahre (1858–1871) (special publications of the Heidelberg City Archives, Vol. 8, edited by Peter Blum). With 52 illustrations. Berlin, Heidelberg 1997
• Franz Werner, To the death of the physiologist and physicist Hermann von Helmholtz , in: Journal for the history of the Upper Rhine. 146 = NF 107 (1998). Pp. 544-551
• Franz Werner, Hermann von Helmholtz (1821-1894) - Fulfilled research life , in: Helmholtz-Gymnasium Heidelberg & Friends of the Helmholtz-Gymnasium (Hg.), 175 years 1835-2010 Helmholtzgymnasium. Heidelberg 2010, pp. 44-69

Commons : Hermann von Helmholtz  - collection of images, videos and audio files
Wikisource: Hermann von Helmholtz  - Sources and full texts

## Individual evidence

1. Barbara I. Tshisuaka: Helmholtz, Hermann Ludwig Ferdinand von , in: Werner E. Gerabek , Bernhard D. Haage, Gundolf Keil , Wolfgang Wegner (eds.): Enzyklopädie Medizingeschichte. De Gruyter, Berlin / New York 2005, ISBN 3-11-015714-4 , p. 566
2. Michael Ruoff: Hermann von Helmholtz . UTB, 2008, p. 87.
3. Axel W. Bauer : Causes or Motives? The dilemma of medical research between scientific and hermeneutic methods. In: Würzburg medical history reports. Volume 17, 1998, pp. 53-63; here: pp. 54–56 ( Rudolf Virchow and Hermann Helmholtz as representatives of the scientific method in 19th century medicine ).
4. Member entry by Hermann von Helmholtz (with picture) at the Bavarian Academy of Sciences , accessed on February 5, 2016.
5. Ellen von Siemens-Helmholtz: Life data of the German National Library
6. Member History: Hermann LF von Helmholtz. American Philosophical Society, accessed September 27, 2018 .
7. Hermann von Helmholtz . In: Theodor Westrin (ed.): Nordisk familjebok konversationslexikon och realencyklopedi . 2nd Edition. tape 11 : Harrisburg – Hypereides . Nordisk familjeboks förlag, Stockholm 1909, Sp. 349 (Swedish, runeberg.org ).
8. Michael Ruoff: Hermann von Helmholtz . UTB, 2008, p. 88.
9. Carl Hans Sasse: History of ophthalmology in a short summary with several illustrations and a history table (= library of the ophthalmologist. Issue 18). Ferdinand Enke, Stuttgart 1947, p. 45.
10. Henning Schmidgen: The Helmholtz curves. On the trail of lost time. Merve Verlag, Berlin 2009.
11. ^ Franziska Roeder, A microscope for time , master's thesis at the Humboldt University in Berlin, 2011.
12. Preliminary report on the propagation speed of nerve stimulation. Archive for Anatomy, Physiology and Scientific Medicin. In: Monthly Report of the Royal Academy of Sciences, pp. 71–73; here: p. 71.
13. Hermann von Helmholtz: About the theory of the composite colors. In: Archives for Anatomy, Physiology and Scientific Medicine. (1852), pp. 461-482.
14. About integrals of the hydrodynamic equations, which correspond to the vortex movements. Celles J 55, 25 (1858) cited and edited in Mechanics of Deformable Media / by Arnold Sommerfeld ; edit by Erwin Fues ... and others - Reprint d. 6th edition. - Thun: Harri Deutsch, 1992. (Lectures on theoretical physics; Volume 2, Ed. 6) ISBN 3-87144-375-1 .
15. Lotte Burkhardt: Directory of eponymic plant names - extended edition. Part I and II. Botanic Garden and Botanical Museum Berlin , Freie Universität Berlin , Berlin 2018, ISBN 978-3-946292-26-5 doi: 10.3372 / epolist2018 .
16. Information from the faculty on the year
17. Helmut Heiber (ed.): The normal madness under the swastika. Trivial and peculiar things from the files of the Third Reich. 2nd Edition. Herbig, Munich 2001, p. 264.
18. Hermann von Helmholtz (1821-1894) - A trailblazer in psychology . ( uni-wuerzburg.de [accessed on September 11, 2018]).