HERMANN VON HELMHOLTZ-I.

Evening Star, Issue 16051, 1 March 1916, Page 8

HERMANN VON HELMHOLTZ-I.

~ [By James Collide.] - [Special Rights Secured by the 'Star.'] The great savant was born at Potedam on August 31, 1821, almost at the very heart'of tho Prussian bureaucracy. To that relentless organisation hia father, a distinguished instructor in philology, with the State-title of professor, at the gymnasium (high school or university college) of Potsdam, was for 37 years the devoted slave, who dared not speak above liis breath; and his illustrious son, with the very physiognomy of a Bismarck; was intrinsically a man of the same type. Like his equally illustrious fellow-countryman, Alexander Von Humboldt, who "learnt nothing before he was eight" years old, he was a delicate child for his first seven years, and was late in going to school. But even then his future greatness was foreseen, and keen-eyed relative predicted that his career would rival.that of Humboldt. It was even so, and still greater were his achievements. —His Training.— As we read, we are impressed with the thoroughness of "the instruction of *the German academic in all branches, its breadth and its depth. Nothing comparable with it could probably be found in any other country. His father's initiatory private tuition was admirable. The gymnasium was as efficient as an English or Scottish university. There Humboldt learnt, besides the ordinary subjects, French, English, and Italian, even Hebrew and elementary Arabic. And, like so many Germans, he acquired the ability to play classical music. But his preferred subjects wore chosen among the physical sciences—physics and optics, botany," anatomy, and zoology; he studied the passing of the rays of light through the telescope and optical problems. With all his accomplishments, Helmholtz's vocation was manifestly for science, and at 15 he told Ids father that lie intended to devote himself to that. This he could do only if he were educated to be an army surgeon. The Government took him in hand, and placed him in the Royal Institute of Medicine, where • army surgeons were trained. The education given them there had the same character of thorouehness as at the gymnasium. There Helmholtz attended 48 lectures in the week, which included such outside subjects as logic, physics, history, Latin, ar.d French, while he privately read Kant and the second part of 'Faust,' by way of recreation, we presume. In addition to it all, Helmholtz took lessons in swimming and fencing. —His First Discovery.— At 21 Helmholtz took his doctor's degree, and in connection with it he made his first discovery. In 1833 the great microscopist, Ehrenberg, discovered" the ganglion cells in animals, and now this brilliant youth proved that the nerves originate in these ceils-. This discoverv is recognised by all physiologists as the basis of nervous physiology. Helmholtz thus established the connection between nervefibres and nerve-cells, and at the same time the central characters of these cells. These are remarkable discoveries to have been made by so young a man. —Conservation of Force.— Appointed house surgeon at the Charite Hospital in Berlin, and afterwards to the Hussars at Potsdam, Helmholtz continued his scientific labors and his intercourse with his great teacher, Johannes Mueller, and his perhonal friends, Du Bois Reymond, Briiecke, and Ludwig.' The great topic that chiefly occupied him was° the Conservation of Energy. He first broke ground on the subject in his student days, and now, in 1847, he sent to Reymond a sketch of the introduction to'a treatise on that theme. Du Bcis declared that it was "an historical document of great scientific import for all time." On July 21 he read his memoir at a meeting of the Berlin Physical Society. It re°veakd him as a master of mathematical physics. It was not received with unmixed ..approval. Indeed, the older men almost unanimously rejected the ideas expounded in it. Tho younger physicists and physiologists enthusiastically welcomed it, and the gifted mathematician, J. J. Jacobi, supported them. Helmholtz believed that he was the first to set forth a universal law of experimental science. He was unaware that he had been anticipated by Julius Mayer, Colding, and Joule, which last had experimentally proved it in connection with heat. Nature as a whole, .he held, possessed a store of energy that cannot be increased or diminished; " the quantity of energy in inorganic nature is as eternal and unalterable as the quantity of matter." This universal principle Helmholtz called the law of the Conservation of Force, and in so naming it he was followed by Herbert Spencer. But Thomson and Tait, who defended the priority of Joule, and used the term Conservation of Energy, while Tyndall vindicated the rights °of Mayer, and Helmholtz afterwards admitted the partial priority of Mayer, distinguished between force and energy, a distinction which the Germans, with Helmholtz at their head, accepted. By the sixties the law was evervwhere adopted, and since the seventies "it has been axiomatic. Now the concept is itself disputed. That brilliant free-lance, Dr Le Bon, has, he imagines, proved that energy does not necessarily persist, and later physicists are now seeking to prove that matter is not indestructible. —Physical Measurements __ Appointed professor of physiology at Koenigsberg, Helmholtz was "but beginning the ascent of the ladder whose | highest rungs he was one day to reach. His adventurous spirit soon carried him far in another direction of research. His honored master, Mueller, only six years before, had declared that we should never bo able to ascertain the rate of the propagation of impulses in animal and human nerves. Why? Because we had no proper means of experimenting over, such enormous distances as were requisite in determining the _ velocity of light. The data in the activity of the nerves and the time taken"" by the passage of a sensation, or afferent current; travelling. from the remote ends of the sensory cutaneous nerves to the brain, and the efferent current passing from the brain to the muscles—all such data were lacking or were " too infinitesimal." Helmholtz was not to be discouraged. He experimented on frogs, r..nd found that the rate of excitation through nerve io muscle is more than ton times less than the velocity of sound in air. It was a triumph, or the first of a series of triumphs, where his great naeter had predicted failure. . At ■ the beginning of 1850 he sent to Du Bois Reymoncl a memoir on the rate of transmission in nerve. Again Du Bois wag his only sympathiser. "'Your work," ho wrote to his friend, "is understood and recognised in Berlin by myself alone." Mueller would have nothing to do with the research. Nor would Humboldt. Fven Dove and Magnus, his friends, were unfavorable. Thus the physicists were at first against liim, and the philosophers were strongly opposed. Tho academicians of. Paris did not receive the idea well. This state of things did not last very long. Both Humboldt and Mueller were iipeedily converted. Helmholtz continued his experiments on frogs, to which he added bis' experiments "on himself and others. Ho estimated the rate of propagation in the sensory and motor nerves of man at from 50 to 60 metres per second more than twice the rate of transmission in frogs. His work on time measurements opened up new and boundless vistas and fields o"f investigation " for physiologists. The researches and experiments of Fechner, Wundt, Munsterberg, and their students,, which, have since played so great a part, were based-on Helmholtz's inquiries. i —The Ophthalmoscope.— j The end of the year thus gloriously begun was crownrd by a casual but important invention, which he called a discovery. The ophthalmoscope revealed a new world to the students of the eye and practitioners in that department. It is a combination of glasses that makes it possible to illuminate the dark background of the eye through the pupil. A view of all the elements of the retina can thus be obtained at once. The blood vessels and all their branching arteries and .veins are displayed. The minute.investigation of the internal structures of the eye became practicable. Even were at first very shy of using th?

possibly dangerous instrument, but it soon came into general U6e, and it has ever since been the chief stand-by of the ophthalmist. The invention was, as he confessed,, the turning-point of his fame, and he was now left free by his colleagues and the au-. thorities to take his own course. —Physiological Optics.— It was natural that, with such an instrument in his hands, Helmholtz should turn to such a theme as the theory of compound colors. Ho first examined, and he belied (perhaps it is generally believed) that he refuted, Sir David Brewster's new analysis of solar light. In a memoir he laid the foundations of the whole modern physiological theory of color, and he contributed a mass of new points of view, methods, and results to the science of physiological optics. From these, by a long series of conclusive experiments,* he developed his entire theory of knowledge. "Sensations of light and color," he contended, " are only symbols for relations of reality." They give us no real information about the external phenomena. That such an investigator- should discover a hitherto unknown alteration in the human eye when performing the act of " accommodation" is no more than we expect. He it was, too, who discovered that the so-called invisible rays of the spectrum can be detected by the human eye, and it was he who named them the ultra-violet rays. Taken in connection with the invention of the ophthalmoscope, these views worked revolution in the optics of the eye. No one, said Du Bois Reymond, has ever united the fullest mathematical and physiological knowledge of optics with such a mastery of the anatomical conditions as Helmholtz. He first explained'the natare of lustre, and showed that the sensation from each eye arrives separately at consciousness. He set forth and inteipreted the laws he had discovered in physiological optics. He brought forward his theory of sense-perception in man as being purely empirical, though he was strangely in error when he assumed that this is the doctrine of Kant. He also launched out against Hegel's metaphysical philosophy of Nature, which had for its chief advocate Hegel's leading disciple, Rosenkrantz, then a at Koenigsberg. To Helmholtz sensations were mere signals to consciousness of changes in the outer world, but not images of those changes. —At Bonn.— In 1855 Helmholtz wae appointed' by the Prussian Government to be professor of physiology and anatomy at Bonn, there were two rival professors,- and in 1856 (will it be believed?) Helmholtz was reported to the Ministry on account of the inadequacy of his lectures on anatomy. It was, of course, an invention. The new professor had scared the old school by introducing a good deal of chemistry and physiology into his teaching of; anatomy. He made a great advance by publishing in 1856 part 1 of ids 'Physiological Optics.' There (to mention only one point) he elaborated the conclusion he had much earlier arrived at, that the structure of the human eye is hopelessly imperfect. In later years he pronounced still more' decidedly. Did an optician, he said, send' me such a defective instrument,. I would return it to him and ask back my monev. Meanwhile he proceeded from optics to acoustics, with the view of establishing that the other sensations, especially those of hearing, were as purely subjective as those of sight. He aimed at constructing a whole new theory of harmony. He endeavored to show the connection of musical' sounds with partial differential equations. So he told his chief German correspondents. His chief British correspon- [ deat, Ik>rd Kelvin, he informed <Jf hj^

observations on the combination of tones. He thus began the researches that were to lead to one of his most striking discoveries. Here he took the same step as he had taken in optics. As the perception of an object is built up from the two distinct images on the retinas of both eyes, a compound tone consists of a dominant prime tone and certain overtones. This was the result arrived at in 1857. Helmholtz now ran his two chief horses abreast, and made a rapid succession of discoveries in both acoustics and optics. He told Du Bois that he had accumulated materials for the reform of physiological acoustics. He continued to elaborate bis theory of vowel tones. He or his wife would sing the ground tone into a piano. Then the third and fifth tones were heard plainly at the same time, while the second, fourth, and) seventh were weaker. These overtones give rise to what is called timbre; he ascertained their physiology, and he succeeded in detecting them and in making others hear thorn.