HELMHOLTZ, HERMANN LUDWIG FERDINAND VON (1821-94)

This remarkably versatile scientist, who made many pioneering contributions to physiological psychology, was bom in Potsdam, Germany, and was educated at the Friedrich-Wilhelm Institute for Medicine and Surgery in Berlin. After completing his studies, Helmholtz served as an army surgeon for seven years (1842-49). His medical dissertation, written at the age of twenty-one, adumbrated the neural theory by showing that ganglionic nerve cells are individually connected to separate nerve fibers. This work helped to gain him admittance to the inner circle of scientists at the University of Berlin, which included H. G. Magnus, the physicist, and Johannes Muller, the greatest physiologist of the time.In 1845 Helmholtz and three other outstanding scientists, Ludwig, Briicke, and Du Bois-Reymond, formed a pact to fight the doctrine of vitalism, which recognizes other than organic forces as the basis of life. His own support of the mechanistic view took the form of a paper “Uber die Erhaltung der Kraft,” which attempted to show that the workings of the body are subject to the law of “conservation of energy.”From 1849 to 1856, Helmholtz served as professor of pathology and physiology at Konigsberg. In an early series of experiments he used a device he called a myograph to measure the speed of nerve conduction in a frog. The same technique was then applied to human subjects by varying the point of stimulation (the toes, the thigh, etc), and measuring the time differentials in obtaining a response. From these experiments—which were actually the first studies of reaction time—he calculated the transmission rate for sensory impulses at between 50 and 100 meters per second, with wide differences between subjects and within the same subject at different times.These experiments had far-reaching effects. They upset the opinions of the experts, some of whom believed the impulses traveled at many times the speed of light, claiming that “we shall probably never obtain the power of measuring the velocity of nerve action, for we have not the opportunity of comparing its propagation through immense space, as we have in the case of light” (Miiller, 1843). More significantly Helmholtz’s experiments showed that events within the organism, which most people believed to be immeasurable and directed by the soul, could actually be investigated in the laboratory. Boring (1950) makes this comment in his History of Experimental Psychology: “In Helmholtz’s experiment lay the preparation for all later work of experimental psychology on the chronometry of mental acts and reaction time. The most important effect of the experiment and all the research that followed upon it was, however, that it brought the soul to time, as it were, measured what had been ineffable, actually captured the essential agent of mind in the toils ofscience.” See REACTION TIME, NERVE CONDUCTION.While at Konigsberg, Helmholtz also began to apply himself to the scientific study of vision, inventing the ophthalmoscope and ophthalmograph to aidhim in investigating the internal mechanisms of the eye. He continued hiswork at the University of Heidelberg, where, as professor of physiology, he published the first edition of his Hand- buch der Physiologische Optik (1867), which is still a fundamental text. This work reviewed all previous studies on optics, brought together recent findings and principles, and presented the results of original experimental investigations on the external muscles and the internal focusing mechanism of the eye.In the Optik, Helmholtz also introduced a theory of color vision which extended the earlier findings of Thomas Young. In addition, he sought to explain perception by applying the concept of “unconscious inference.” In essence, this concept meant that we do not directly perceive external objects, but only nervous excitation; however, when certain patterns of excitation are repeatedly associated, we automatically and “irresistibly” infer that they constitute actual objects. See COLOR VISION THEORIES.During the years at Heidelberg, Helmholtz also turned his attention to the study of hearing, publishing his classic volume Die Lehre von den Tonempfindungen in 1963. This work wastranslated into English under the title Sensations of Tones in 1875, and is still consulted by students of music, physiology, and psychology. It proposes the resonance, or “place,” theoryof audition, explains the nature of timbre, beats, discord, harmony, and many other acoustical phenomena. Helmholtz was also greatly interested in the history of music, and traced the dynamics of harmony from Greek times to the more completely integrated relationships of the 19th century. See HEARING, HEARING (THEORIES).In 1871 Helmholtz became professor of physics at the University of Berlin, and was appointed president of the university in 1877. He remained there for the rest of his life, workingprimarily in the areas of hydrodynamics, meteorological physics, and theories of electricity and electrodynamics. His contributions to these fields are considered as creative and brilliant as his work on nerve conduction, optics, audition, and music.Helmholtz richly deserves the appraisal of Lindskog (1966), who characterizes him as “One of the last great universalists of science, (who) was able not only to unify the practices and teaching of medicine, physiology, anatomy, and physics, but to relate these sciences significantly to the fine arts.”