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Ernst Mach

as vertic.il and unconsciously infcr thc inclination of ihe trccs. Of coursc thc oppositc condusion that we rcgard thc trccs as vcrtical and infcr thc inclination of thc carriagc, unfortunatcly, is cqually elear on this theory. . . . [Rcjccting Hclmholtzs theoryJ I inferred that thc dircction of thc total rcsultant physical accclcration of thc body rcacts physiołogically _as thc Ycrcical.¹®

In other words, be thought that thc dircction of accelcration deter-mincd not only what we feel is vertical but also what we sec and other-wise sense is vcrtical.

But as so often happens in science, thc original brainstorm that stimulatcd his thinking and experimcntation toward significant dis-coveries was itsclf unsound. In this casc, Josef Breucr and Alois Krcidl were later to show that the optical distortion of thc vcrtical depended on an involuntary reflcx wheel-like movcmcnt of thc cyes. In other words, ncithcr thc explanation of Hclmholtz nor that of Mach turned out to be adcquate. Mach, howevcr, in the blissful enthusiasm of his own idea, decidcd to put it to an experimcntal test (1873) and from this much that was unexpectcd devclopcd.

Ernst Mach constructcd (or his laboratory mechanic Franz I łajek constructed it for him) a whirling chair madc of wood within a double wooden frame. It vaguely rescmblcd today’s Link trainers and astro-naut centrifugcs.¹⁷ When the scated obscrvcr was spun on the sec-ondary axis of rotation his impression of visual verdcality seemed to changc in a way to support Maclfs theory, but when hc was rotated on the primary axis Mach began to noticc a different phenomenon. A paper box was placed ovcr his head and when thc speed of rotation was either inereased or decreascd he fclt a sense of motion. When the speed was constant, howcver, hc ccascd to feel any motion at all, no morc than hc would havc had he been at rest. Mach was intrigucd. He had discovcred a sense of motion, a “sixth sense,” though of coursc this sense and dizziness had naturally been notieed by other people beforc. Not stopping with describing its characteristics, he then inquircd about its ‘parallel" physical countcrpart or cause.

The question now arosc what particular organ might function in such a way as to arousc a fccling of motion only when there was bodily accelcration or dccclcration. According to Mach, hc cxpcricnced “a pcrfcct illumination."¹⁸ ‘‘My juvcnile expericnccs of vertigo oc* currcd to mc. I remembered Flourcn's experimcnts relntive to the sec-tion of thc semicircular canals of thc labyrinths of doves and rabbits,

whcre thc observcr had obscrvcd phcnomcna simibr v ■    ,

whicl. hc prcfcrrcd to intcrprct, from his bias to [ Helmho J-T’ ^

Furthcrmorc, Mach vagucly rcmcmbcrcd that F L G| ,

1870. had asscrtcd that whilc it was unccr.ain whc.hcr thc scmLodar _Canals arc aud,.,vc organ, or not it was a. Icast elear that they w ncccssary for bod.lv cqutl.br.um, They werc, so ,0 speak, “the sense „rgans of cqu.hbr.um of thc head and indircctly of thc wholc body ”

Mach now a,temp,cd to study the struc.urc of the scmicrcubr canals thcmsclvcs, but herc hc ran into a seriom problem Mach was not an cxpctt ,n anatemy or human physiology, and furthcrmorc hc was an ant.v.visccdonist. But without skillful surgery how was hc going to understand thc cxact charactcristics of a tiny organ locatcd dccp with.n our hcads? Surcly animal viviscction was an indispcnsable tool for sc.cntific insest.gation. But Mach would not budec He drnict both its ncccssity and desirability.²⁰

Prcsumably, Mach learned the rcquisite structural Information on thc labyrinth from books written in large part by authors who themsclses had engaged in viviscction and learned many things from it. But in any casc, hc soon arrivcd at what he thought was thc answer. It was inertia hclping to press semicircular canal liquid against reccptors in the ampullac which causcd thc fecling of motion. When therc was no accelcration or deederation, inertia ccascd to force thc liquid and therc was no fecling of movcment at all.

In spite of thc plausibility of Mach’s explanation, howeser, it aroused a good tlcal of criticism, cspecially from scicntists who fasored vivi-scction, or at least who saw no satisfactory altcrnativc to it.

On thc other hnnd. Mach*s priority of discovcry turncd out to be only a matter of days. Mach’s paper was rcccivcd on Novcmbcr 6, 1873. by thc Austrian Acadcmy of Science, Josef Brcuer‘s paper on November M» ^,87h ^by ⁽bc Austrian Imperial Society of Doctors, and that of Pro-fessor Crum Brown of Edinburgh on January iq, 1874.⁹¹ AU threc men worked indepcndcntly, with Brcucr cspecially using a dirterent tvpc of approach. Mach was interested in thc "psychophysical“ relation between a fecling and a bodily organ whilc Brcucr emphasized com-parative anatemy, and carefully examincd organ structurc. It is p<\$-siblc that this cxpcrimcntal work hclpcd persuadc Mach finally to abandon Fcchncr’s particular understanding of “psychophysical parallclism**

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