Early days of the tuning fork
Neurologists have for many years used the tuning fork both as a crude test for hearing, by means of the classic tests of HA Rinne (1819–1868)1-3 and Weber-Liel (1832–1891), and for vibration sense. In Pavia, Italy, G Cardano, astrologer, physician, and mathematician, in 1550 suggested that sound could be transmitted through the bony skull as well as through the air and a few years later, H Capivacci, a physician in Padua, used this phenomenon as a means of differentiating between middle ear and nerve deafness.4 The technique was then used by a German physician G C Schelhammer in 1684 who used a simple table fork. But, the study of ear diseases was in its infancy and little progress was made for two centuries.
The tuning fork was invented in 1711 by a John Shore, trumpeter and lutanist to both Henry Purcell and George Frederick Handel in London. The tuning fork found a place as a musical instrument employed in the concert halls, churches, and chamber music ensembles throughout Europe. It started as a small steel instrument consisting of a stem with two stout flat prongs, which on being made to vibrate produced a musical note of constant pitch, thus serving as a standard for tuning musical instruments and in acoustic investigations. In 1799 Young observed5: “The fundamental note was found to be one sixth of a tone higher than the respective octave of a tuningfork marked C”
E F F Chladni, a physicist in Wittenberg in about 1800, first systematically studied the mode of vibration of the tuning fork with its nodal points. Using sets of tuning forks, he made a musical instrument that failed to achieve popularity. J H Scheibler in Germany in 1834 produced a set of 54 tuning forks with a range of 220 Hz to 440 Hz, at 4 Hz intervals. In Paris, J Lissajous created a tuning fork with a resonance box, intended to represent the international standard of the note with 435 vibrations per second, but this too was not generally accepted.4 K R Koenig, a Parisian physicist, devised a clever clockwork mechanism which produced a continuous vibration and sound in the tuning fork. Hermann von Helmholtz in 1863 also used sets of electromagnetically powered tuning forks to elicit the sensations of tone. Until the electronic valve, the tuning fork was the only instrument that produced sinusoidal vibrations of standard duration.
Huizing6 7 has reviewed the early papers on tuning fork tests of deafness. He relates that in 1855 Rinne compared hearing by air and bone conduction, and used the tuning fork for the diagnosis of deafness. However, before Rinne, Polansky in 1842 gave a detailed but forgotten description of the test and of its application in deafness. Schmalz in 1849 had made similar observations. Curiously, Rinne’s report was also lost until Lucae (1880), Emerson (1884), and Schwabach (1885) confirmed the value of his work, since when it has retained the name of Rinne but not of Polansky.
The concept of proprioceptive function, developed by Landry, Bell, Bastian, Ferrier, and others in the 19th century, advanced at the turn of the 20th century, and was further advanced by Sherrington8 and later Haldane9: “The receptor organs are those parts of the living organism which are specially sensitive to the changes going on around them. Some of them are affected by the changes going on inside the body in muscles and joints and in the organ of balance (proprioceptors), others by the changes taking place in the world outside (exteroceptors).”
Kühne showed the presence of proprioceptive receptors in muscles (“Kühne’s spindles”) in 1862–3.
In Gowers’ textbook of 188810 we find tactile, thermal, and pain sensory tests but he omits the sense of vibration. It was not until the beginning of the 20th century that tuning forks were applied to bony prominences and muscles to elicit “vibration sense” which was recognised as a crude method of testing neural pathways similar to those used in proprioception. Vibration was but repeated touch.11
The use of the tuning fork to clinically test vibration sense is generally credited to Heinrich Rumpf, professor and director of the poliklinik in the University of Marburg, who published his findings12 in 1889*. A controversy surrounded its significance. Tomson, Treitel, Rydel, and Seiffer argued that it was a discrete sensation, sometimes impaired when touch and pressure sensation were preserved, in tabes and polyneuritis. Egger13 in Dejerine’s clinic, and Schwaner, thought that the receptors lay in the periosteum but the sensation (pallaesthesiae) was conducted by bone. However, vibration sense was not generally accepted as a valid clinical test for another 10 years.14
The idea of bony sensibility— ignoring the sense of vibration when a fork was applied to soft tissues— dominated neurological concepts for many years. In the presence of posterior column and peripheral nerve lesions physicians discovered vibration sense to be impaired, although it is evident that vibration perception is a physician’s tool stimulating rapidly adapting mechanoreceptors conveyed both in posterior columns and corticospinal pathways in the cord. Transmission of several proprioceptive modalities, not limited to the posterior columns, ascend and are integrated and perceived at a higher level. There is no known corresponding physiological function.
The empirical use of vibration sense tests has, however, not been superseded. In modern times physicians employ many refinements for measuring vibration thresholds that include the
Rydel-Seiffer graduated tuning fork,15biothesiometer, vibrameter, and the Optacon tactile tester, which provide quick and fairly reliable assessments.
↵* I am indebted to Dr Nikolaus Arts of Nijmegen, The Netherlands, for this source and information.