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Ernst Mach

A numbcr of scientists indcpcndcndy rcdiserwered thcsc bands dur-ing thc 1890s but wcrc morc mystificd than not by them. An astron-omcr wondcrcd why thc cnrth’s shadow secmcd largcr than it should be during a lunar cclipse; two scientists werc pcrplexed by unantici-pated “intcrfcrcncc" fringes on X-ray picturcs.⁸ C. H. Wind madc strides toward clarification and for a while thought that hc had bccn the first to discovcr the bands. In 1899. howcvcr, hc accidcntally learned of Mach’s work and in generous fashion both admitted Machs pri-ority and gavc them their currcnt nonie, Mach bands.

This rencwed interest in the bands and in Mach’s old work soon camc to Mach’s attention. It so cncouraged him that hc returned to thc subjcct and in spite of physical disability published yet another articlc to cxpand and further clarify his vicws.¹⁰ In fact, howcvcr, thc fuli significancc of thesc intensity lines was still by no means fully grasped. Mach bands gradually bccamc recognizcd as phenomena that thc carc-ful obscrvcr would havc to watch out for so as not to be confuscd as to what was “objcctivcly” therc. The conncction with ncurological in-hibition and c.\citation, howcver. continued to be ignored almost com-plctely.

Georg von Bćkesy (1899-), thc futurę Nobel Piizc winner, sug

gested in 1928 that therc might be “subjective" phenomena similar to Mach bands outsidc the visual system. And indeed, just such phenomena werc cvcntually discovcrcd in auditory reccption, and they too havc bcen related to ncurological inhibition.

In 1951, after a meeting with von Bekesy, Floyd Ratliff was encour-

DIACRAM 3.

Mach bands as graph dcviations betwccn obscrved and calculatcd color intensity.

(Conrtesy of HolJen-Day hic.)

agcd to inąuirc further into thc mathcmatical relationshin, k,

Mach bands and neurologio! inhibition. "The rcason f„_r J J^ngly bclatcd development of „ucresr ,s that only within thc last _quar,cr cen tury or so have the tcchm_qucs of dcc.rophysiology frnally Lome sut ficrcntly adsaneed to prov.de a sound cmpirica! foundation for such studics.

Professor Ratliff has rcccntly written Mach Bond, (San Francisco _ly6₅), a vcry informativc book on contcmporary incest,gations i„,ó thcsc odd phenomena. The book also indudes English translations of Mach s hard-to-gct art.clcs, as wcll as a lengthy account of Machs lifc philosopny, and other scicntific work.

Labyrinth Funclions and Sense of Moiion

Mach¹* carly "psychophysical" atlcn.pts to relate hcaring with car structure and sense of motion with human physiology werc not succcss-ful. He tried, for examplc, tu (ind out if middle car musclcs had audb tory as wcll as mechanical functions. Hc was disappointed.¹² In one CJtperiment hc cvcn poured atropino and carbonic acid into thc car of a patiem to paralyzc thc musclcs temporarily, but in his own words evcn this “Hamlet sccnc" failed to bring rcsults. I.ittle of Mach's work in this arca was cver published.

Mach dcvclopcd two succcssive theorics on motion as a feeling. He first becamc interested in thc subjcct “on thc occasion of a scrics of cxpcriments on licjuids which containcd suspended particlcs [1865?]. which one of my pupils performed at my instigation.”¹³ Machs appar-ent discovcry that the measurable charactcristics of thc particles, in-cluding perhaps their weight, werc at least partly dependent on their acccleratiun, led to his first rhcory, that thc whole human body con-tributed to thc sensation of moYerr.cnt.¹ *

Apparcntly, Mach had no suspicion at this timc that a particular bodily organ might be responsiblc. His “psychophyśical" tcndency to look for rncrc relational constancies instead of for particukir physical connections did not >crve him wcll at this timc. For about eight ycars his progress in this arca was slight.

Mach remembered thc beginning of his breakthrough wcll:

On rounding a railway curvc oikc, l accidcntly obserycd a striking ap* parent indination of thc houses and trees.¹⁵

For thc popular explanation by unconscious inferenee [Hclmholtzs thcoryl thc matter is extrcmely simplc. We regard thc railway carriage

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