Seeing with the skin

BENJAMIN W. WHITE,2 FRANK A. SAUNDERS, LAWRENCE SCADDEN, PAUL BACH-Y-RITA,AND CARTER C. COLLINSPACIFICMEDICAL CENTER

A system for converting an optical imageinto a tactile display has been evaluated tosee what promise it has as a visualsubstitution system. After surprisingly littletraining, Ss are able to recognize commonobjects and to describe theirarrangement inthree-dimensional space. Whengiven controlof the sensing and imaging device, atelevision camera, Ss quickly achieveexternal subjective localization of thepercepts. Limitations of the system thus farappear to be more a function of displayresolution than limitations of the skin as areceptor surface. The acquisition of skillwith the device has been remarkably similarfor blind and sighted Ss.

Twelve years have passed since thepublication of Geldard's (1957) provocativepaper in which the potentialities of the skinas a communication channel weredemonstrated. Since that time, Geldard andhis colleagues have refined their techniqueof presenting highly discriminablevibrotactile stimuli to various parts of thebody. In a recent report, Geldard (1968)describes the application of nine vibrators atwidely separated body sites, each onetriggered by one photocell in a linear arrayscanning typed and printed characters. It ishoped that this system will enable trained Ssto read at speeds comparable to those thatGeldard reported earlier, using a set of fivevibrators mounted on the chest and capableof delivering signals at three intensities andthree durations. After a few hours oftraining with this sytem, Ss were able toreceive material at a rate approximately

twice that of proficient Morse codeoperators.

Geldard's efforts have been orientedexclusively toward the use of the skin toreceive a set of known and clearlydiscriminable characters, whose optimalcoding has been determined bypsychophysical techniques. The possibilityof using the skin as a channel for pictorialmaterial has not been systematicallyexplored, though devices capable ofpresenting dynamic two-dimensional tactileimages exist (Linville & Bliss, 1968,Strakiewicz & Kulizewski, 1965). Thepotential utility of such devices as visualsubstitution systems for the blind isimmediately apparent. It is surprising that inthis day of advanced technology, the blindare still moving about in the world using acane, a guide dog, a sighted companion, oran outstretched hand.

In addition to its value as an aid for theblind, such a tactile image system providesan opportunity to explore a number ofsuchperceptual phenomena as size constancy orspace perception that heretofore have beenconsidered uniquely visual. Also, theproblems people encounter in gainingfacility with this novel system should throwlight on aspects of perceptualleaming thathave thus far been difficult to investigate.

For the past year, we have been workingwith a sensory substitution system thatconverts avisual imageinto a tactile one. It isthe purpose of this report to present some ofthe initial findings from this work and todiscuss their implications for perceptualtheory.

METHODSThe theoretical neurophysiological basis

(Bach-y-Rita, 1967) and the physicalconcept of the instrumentation (Collins,1967) for the vision substitution systemhave been discussed previously. Preliminaryresults in training blind Ss to use theapparatus have been briefly reported(Bach-y-Rita et al, 1969a; Bach-y-Rita etal,1969b;Scadden,1969;Saunders, 1969).

As shown in Fig. I, the "eye" of thesystem consists of a television camera. Thiscamera, which is mounted on a tripod, ismanipulated by the S, who can aim thezoom lens at any part of the room, in orderto localize and identify objects or persons.Stimuli can also be presented on a back-litscreen by slide or motion picture projection.The video image is electronicallytransformed and sent to a 20 by 20 matrixof solenoid vibrators mounted in the back ofa stationary dental chair. The 400stimulators, spaced 12 mrn apart withI-mm-diam tips, cover an areaapproximately 10 in. square. Each solenoidis designed to vibrate at 60 Hz when its locusis within an illuminated region of the camerafield. The on-offactivity of the vibrators canbe monitored visually on an oscilloscope as atwo-dimensional pictorial display.

The Ss for this series ofexperiments wereyoung adults, many of whom were from anearby college. Twenty-five congenitallyblind men and women have been tested inthe apparatus, in addition to five adults whowere blinded later in childhood. Over 50sighted Ss have also been examined. Not allof these Ss have been put through all theprocedures described below. Eight blind Sshave had over 40 h of training in the chair,while others have come in to serve as Ss for asingle experiment.

RESULTSSubjects are able to perceive certain

simple displays with this tactile system,ahnost as soon as they have been introducedto it. If a white circular target, capable ofactivating approximately three-quarters ofthe tactors, is placed before the camera, Sshave no difficulty in centering the image onthe tactor array by manipulating the carnera.If a vertical white stripe is moved from sideto side, the S is able to describe the motion

Fig. 1. Schematic representation of thetactile television system.

Perception & Psychophysics, 1970, Vol. 7 (1) Copyright 1970, Psychonomic Journals, Inc., Austin, Texas 23

Table 1Comparison of Tactile

and Visual Slant Judgments

Fig. 2. Representation of the visualdisplay which continuously monitors thestate of the 400 tactors.

Observations of Experienced Blind S8Seven congenitally blind Ss have each had

over 40 h of experience in the visionsubstitution system. These men and womenhave been studied intensively because theyproved adept with the apparatus and were

2.8 sec

Latency

8.4 sec

Accuracy

83%(n = 240)

97%(n = 240)

Slant JudgmentsThe same groups of blind and sighted Ss

were asked to make slant judgments basedagain upon slide-projected displays of acheckerboard that had been photographedat a 7Q.deg slant from frontal parallel. Thisslide was projected in one of fourorientations by simply rotating the slide inthe projector. On 40 such randomizedpresentations, the S was asked to judgewhether the checkerboard tilted away to thetop, bottom, left, or right. The results forthis task are shown in Table 1. The blind Ssusing the tactile display made significantlymore errors and took significantly longer tomake their judgments than the sighted Ssusing the visual display. Unlike thevertical-horizontal bar orientation task, theblind Ss all used scanning of the camera tomake the slant judgment. Since this scanninghad to be done by turning two wheels on thetripod, this probably accounts for much ofthe latency difference. The accuracy of theexperienced blind Ss is high on this task andthe accuracy of the sighted Ss is not perfect.This would indicate that the limitations onthe tactile system thus far probably are morea function of the resolution of the displaythan ofthe sensitivity of the back.

not from the tactile input, but from thevisual display seen on the oscilloscopemonitor. Figure 2 shows the kind of visualdisplay the sighted Sswere given.

The two groups showed remarkablysimilar performance. There was only oneincorrect judgment out of a total of 480.The blind Ss had a mean latency to correctresponse of 1.2 sec as compared to 1.1 secfor the sighted group Though both groupswere instructed in the control of the cameraand encouraged to move it before making ajudgment, neither group did so to any greatextent.

Blind OsTactile Display

Sighted OsVisual Display

mean response latency of 6 sec. Significantimprovement was found between each18-trial block. When the Ss were allowed topan the camera over the forms and givencorrection, they achieved 100% accuracy inthe third block of 18 trials with a latency of1 sec or less (Bach-y-Rita et al, 1969). Thediscrimination was even more rapidlyestablished when the figures were initiallypresented in pairs for the S to inspect aftertelling him, "The square is on the right andthe circle on the left." After as little as10 min of such training, some Ss couldachieve 100% accuracy in identifying thesethree simple forms. Particularly in earlystages of training, Ss panned the camera sothat the figure came into and passed out ofthe field, suggestingthat the discriminationis largely based upon contour changes in theleading edge of the figure.

Acuity JudgmentsSix blind Ss were asked to judge the

vertical-horizontal orientation ofslide-projected displays consisting offrom 4to 12 pairs of parallel black and white lines.The five displays were presented in randomorder for a total of 40 presentations, and theSs were allowed to scan them with thecamera before making a judgment. Five ofthese Ss were congenitally blind, and thesixth lost sight before the ageof4. They hadhad from 15 to 40 h of experience in thevision substitution system. The performanceof the blind Ss using the tactile input wascompared with the performance of sixsighted Ss who made the same judgments,

Form DiscriminationInitial experiments with form

discrimination showed that performancerapidly improved when Ss were allowed toscan the figures by moving the camera andwere given immediate correction after awrong response. When asked to identify acircle, square, or triangle, Ss' performanceremained near chance levels after 60 trialswhen no correction wasgivenand no cameramovement was allowed. With correction,accuracy reached 60% after 54 trials, with a

accurately or to imitate it with anappropriate hand gesture. Similarly, apropeller motion of the stripe can beaccurately followed or described. Ss can alsodiscriminate between a stationary vertical orhorizontal stripe. When given control of thewheels controlling camera position on thetripod, the horizontal-verticaldiscrimination becomes even easier sinceonly motion orthogonal to stripeorientation produces a detectable change inthe tactile display. If a diagonal stripe ispresented, Ss are able to report whether theupper end is on the left or the right. They arealso able to adjust the camera so that oneend of the line is centered. Ss are able toreport the orientation of a curved line (a6Q.deg arc with a 4-deg radius of curvature)with reasonable accuracy.

On none of these tasks was theperformance of the blind Ss significantlydifferent from that of the sighted Ss whowere, of course, blindfolded while beingtested.

24 Perception & Psychophysics, 1970, Vol. 7 (I)

able to provide valuable insights about itscapacities and limitations.

These Ss were given extended practice inthe identification of a collection of some 2S"things"-a coffee cup, a telephone, astuffed animal. They were encouraged toscan these objects by manipulating thecamera and to try to describe them. Initialscanning was prolonged, a new object oftenrequiring up to 15 min ofexploration beforecorrect identification. This latency droppedsteadily with repeated presentations untilthe Ss were often able to identify an objectwithin 10 sec on its fifth presentation. A"learning to learn" phenomenon wasevident, since new objects took less and lesstime to identify as the vocabulary of objectsincreased.

The experienced Ss, after they had gainedfacility in identifying a number of objects,were asked to describe arbitraryarrangements of objects placed upon a tabletop. The table was placed so that the cameralooked down at it from an angle ofapproximately 20 deg offhorizontal. The Sswere able both to identify the objects on thetable top and to describe their arrangementeven though their placement on occasionwas such that objects at the rear werepartially occluded by those in front.

Obviously judgments of this sort mustmake use of the sort of information that inclassical texts is called "cues for distance."Particularly useful in making judgmentsabout the position of the object in depth wasits vertical position on the display. Thehigher up it was, the farther back on thetable top. This is precisely the informationthat Roberts (1963) found so useful in hisprogram enabling a computer to construct athree-dimensional representation of anobject using only the two-dimensionalrepresentation of it as input.

The congenitally blind person has neverdirectly experienced the relationshipbetween the visual angle subtended by anobject and its distance from the observer.One of the experienced blind Ss was apsychologist who had explained thisrelationship to introductory psychologyclasses for several years. One day, while inthe chair, he experienced the change in sizeof a tactile image as an object was broughtcloser and closer to the camera, and thesudden perceptual realization of thissize-distance relationship came as a genuine"aha" experience. This evidence of sizeconstancy has been found in other Ssas well.Perhaps of greater interest have been theoccasions when Ss have given startled ducksof the head when the tactile image wassuddenly magnified by a sudden turn of thezoom lever on the camera.

One discrimination that some of the Ssfound most difficult to achieve was that ofinternal detail. For such Ss, the detection of

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facial features in photographs or folds infabric followed by many hours the ability torecognize objects on the basis of outsidecontour alone. There appear, however, to beprofound individual differences in thisrespect, and one S, on his first session in thechair, was able not only to detect an internalhole in an object, but to describe its shapeaccurately.

Further evidence of the existence ofpowerful three-dimensional organization oftactile information presented in this unusualmanner is seen in the response some Ss havemade spontaneously to a kinetic depthdisplay. A modified version of the Metzgerapparatus wasused, consisting of a turntableon which two vertical white rods weremounted. This was rotated slowly before thecamera and the Ss were asked to describewhat they "saw." Some sighted Ss, uponfirst tactile presentation of this movingdisplay, have spontaneously described it asmoving in depth. Severalblind Ss were givenexperience with a yoked pair of turntables.On one of these, an object wasplaced withinview of the camera, while the S turned theother freely, experiencing thetransformations that the object underwentwith the rotation. After an hour'sexperience with this equipment, they couldreport accurately the eccentric placement oftwo and three objects on the turntable, andcould also experience rotation in depth withthe Metzger display.

DISCUSSIONThis sytem was constructed in order to

find out whether or not people could makesufficient use of it to warrant its seriousconsideration as a visual substitution systemfor the blind. The most striking feature ofthe initial results with the system is that Ss,blind and sighted, are able, after onlyrelatively short training periods, to identifyfamiliar objects and to describe theirarrangement in depth. Such results are thebasis for cautious optimism about theultimate utility of a visual substitutionsystem. Evidently even a crude 4QO.tactorsystem is capable of providing sufficientinformation to permit construction ofwhatis usually called the visual world. The limitsthus far encountered are attributable to thepoverty of the display rather than tolimitations in the capacity of the tactileperceptual system.

It will be important in subsequent modelsof the system to employ a lighter sensor thanthe present cumbersome television camera, asensor that can be head-mounted so the Scan scan his environment in a morecongenial fashion. It will also be importantto explore new factor configurations.Questions of optimal spacing of tactors andthe resolution required in order to performvarious tasks will require extensive

investigation. Recent experiments indetection of small inner detail indicate thatturning off half the tactors in the arraymakes surprisingly little difference. Asecond version of the system, presentlyunder construction, will embody both alight head-mounted camera and a tactorarray built in a wheel chair, thus giving theuser a modest degree ofmobility and makingit possible to evaluate the system under amuch wider range of conditions than hasbeen possible thus far.

It is clear from these first tests with thevisual substitution system thatthree-dimensional organization of theinformation in the dynamic tactile array iseasily achieved. The demonstrations of thekinetic depth effect on the skin, and the

. instances of startle response to tactilelooming are clear examples of suchorganization in this modality .

In addition to the three-dimensionalinterpretation of motion in tactile displays,the results thus far point to the greatimportance of self-generated motions on thepart of the observer. When asked to iden tifystatic forms with camera fixed, Ss have avery difficult time; but when they are free toturn the camera to explore the figures, thediscrimination is quickly established. Withfixed camera, Ss report experiences in termsof feelings on their backs, but when theymove the camera over the displays, they givereports in terms of externally localizedobjects in front of them. The camera motionhere is analogous to eye movements in visionand this finding raises the interestingpossibility that external localization ofpercepts may depend critically upon suchmovements.

It is at least a plausible hypothesis that atranslation of the input that is preciselycorrelated with self-generated movement ofthe sensor is the necessary and sufficientcondition for the experienced phenomenato be attributed to a stable outside world.The converse of this hypothesis should alsohold-that a lack of correspondencebetween a translation of the input array andself-generated sensor movements shouldresult in experiences that are attributedeither to nonrigid conditions in the externalworld, or to phenomena that have theirperceived origin within the observer. Itwould be of some interest to examineprotocols from stabilized retinal-imageexperiments. Such a stabilization eliminatesall correlation between eye movement andtranslations of the optic array. The findingthat stabilized images fade has usually beeninterpreted to mean that fine eyemovements are necessary in order togenerate stable visual forms. It is possiblethat the stabilized retinal-image results maybe due to the fact that the percepts arisingunder such conditions of stimulation are

2S

localized within the observer rather than inthe outside world. As von Bekesy (1967)points out, we are adept at tuning out suchinternal information as the taste ofour ownsaliva or the sound of the blood in our ears.Perhaps we are equally adept at tuning outvisual phenomena that are uncorrelated witheye movements. Certainly afterimages areapt to disappear abruptly and then reappearseveral times before they fade for good, andthe motes in our eyes are seen only underspecial circumstances.

Whether or not this hypothesis about thebasis for external localization of percepts isvalid, the fact remains that Ss with this visualsubstitution system were seriouslyhandicapped when they could not move thecamera. At first we erroneously assumedthat little or no significant formdiscrimination was possible with fixedcamera, but later experiments disproved thiswhen experienced blind Ss were able tomake quick and accurate judgments of grillorientation without moving the camera.Static judgments of orientation of thecheckerboard patterns were rare, however.The experienced blind Ss found it relativelyeasy to determine the plane of the tilt, ajudgment similar to the bar-orientation task,but had considerable difficulty telling whichedge of the display was near or far. For this,they all employed many scanningmovements of the camera. This suggests thatthere may be some aspects of tactileinformation pickup that depend heavilyupon changes in the tactile array, and in thisrespect operate differently from vision.

The tactor matrix in this system wasarranged in four quadrants, as shown inFig. 3. With such an arrangement, the spacebetween the center columns of tactors was

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Fig. 3. The 20 x 20 tactor array.at least twice as wide as the spacing of theother columns. Interestingly enough, thiswide silent area wasnot evident to any of theSs. If a narrow vertical stripe was movedhorizontally from one side of the field to theother, its path was perceived perfectlysmooth with no jump in the middle, eventhough the tactile image had travelled twiceas far in the same time when it crossed thecenter of the tactor matrix. The fissure inthe tactor array is not comparable to theblind spot in the eyes since in the latter casethis is a gap in the sensor so that informationis not received in this region, while in thetactor-array case there is no gap in thecamera field, just an irregularity in thespacing of the tactors. Both, however, seemto be invisible. It would be of some interestto see how far apart the two halves of thetactor matrix could be placed on the bodybefore a S would report a gap.

Thus far there have been no salientdifferences between the blind and thesighted Ss in their acquisition of skill on thisvisual substitution system. As wasmentioned previously, the relationshipbetween visual angle subtended by an objectand distance from the S is one that the blindhave not experienced directly and thus haveto be introduced to as a "cue" for distance.Some blind Ss have never been taught theshapes of the letters of the alphabet, so inorder to teach the discrimination of suchforms they have to be given an opportunityto handle cutout letters. But on the whole,the similarities between the performance ofthe two groups are far more striking than thedifferences.

The visual substitution system offers aunique vehicle for the study of perceptuallearning. If one accepts a Hebbian position

on the manner in which visual formdiscrimination is established, one would beinclined to expect that proficiency with thistactile system would be tediously acquired,especially for congenitally blind Ss who havehad no previous opportunity to create thecell assemblies and phase sequences thatHebb postulates as the basis for visual formdiscrimination. Another more recent line ofevidence on the neurophysiological basis ofcertain visual discriminations in loweranimals suggests that they may bedependent upon highly specialized andsurprisingly peripheral feature detectors inthe visual system (Hubel & Wiesel, 1962;Lettvin et al, 1959). If such detectors arealso to be found in the human eye, it mightbe predicted that detection of such featuresfrom tactile inputs would be difficult, if notimpossible, since such detectors in allprobability would not be found in the skin.

The Gibsonian (1966) view of perceptuallearning would probably predict that, to theextent a tactile array contained the sametemporal and spatial adjacencies to be foundin the optic array, learning to respond to"the higher order invariances" in tactilestimulation should present no overwhelmingdifficulty. Also, Gibson would expectperformance with the system to improvemarkedly when the observer was free toprobe the environment to pick upinformation. Gibson has repeatedly stressedthe importance of such exploratory activityin perception.

The results to date with the visualsubstitution system support the conclusionthat facility is quite rapidly attained andthat some Ss are able to make highlysophisticated discriminations with it almostas soon as they are put in the chair. Onecompletely naive 5, for example, wasable toreport accurately the shape of a hollowtetrahedron, complete with shape of thespace that formed an internal detail. Thelearning seen thus far is certainly not of theprolonged sort postulated by Hebb in initialvisual form discrimination. Nor have therebeen marked differences between thecongenitally blind and sighted Ss, whichmight also be expected by empiricists likeHebb or Taylor (1962). Also, the results donot lend support to a theory of visual formperception that postulates highly specializedfeature detectors at the retinal level, thoughthe drastically impoverished display in thepresent tactual system makes anyconclusions in this regard only tentative.

In the past, many efforts at providinginformation to the blind have been basedupon hopelessly old-fashioned ideas aboutthe way the perceptual system works. Inpsychological prehistory there used to be adistinction between sensation andperception. The former had to do withstimulation of end organs that sent their

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messages to the brain where they weresynthesized and correlated through longexperience until a percept emerged. Manyefforts at creating sensory aids are still hungup on this antique notion and set out toprovide a set of maximally discriminablesensations. With this approach, one almostimmediately encounters the problem ofoverload-a sharp limitation in the rate atwhich the person can cope with theincoming information. It is the differencebetween landing an aircraft on the basis of anumber of dials and pointers that providereadings on such things as airspeed, pitch,yaw, and roll, and landing a plane with acontact analog display. It is the differencebetween Skinner and John Holt. It is thedifference between Titchener and Koffka.Visual perception thrives when it is floodedwith information, when there is a wholepage of prose before the eye, or a wholeimage of the environment; it falters whenthe input is diminished, when it is forced toread one word at a time, or when it mustlook at the world through a mailing tube. Itwould be rash to predict that the skin will beable to see all the things the eye can behold,but we would never have been able to saythat it waspossible to determine the identityand layout in three dimensions of a group offamiliar objects if this system had beendesigned to deliver 400 maximallydiscriminable sensations to the skin. Theperceptual systems of living organisms arethe most remarkable information-reductionmachines known. They are not seriouslyembarrassed in situations where anenormous proportion of the input must befiltered out or ignored, but they areinvariably handicapped when the input is

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drastically curtailed or artificially encoded.Some of the controversy about the necessityof preprocessing sensory information stemsfrom disappointment in the rates at whichhuman beingscan cope with discrete sensoryevents. It is possible that such evidence ofoverload reflects more an inappropriatedisplay. than a limitation of the perceiver.Certainly the limitations of this system areas yet more attributable to the poverty ofthe display than to taxing theinformation-handling capacities of theepidermis.

REFERENCESBACH-y-RIT A, P. Sensory plasticity: Applications

to a vision substitution system. ActaNeurologica Scandinavica, 1967,43,417-426.

BACH-y-RITA, P., & COLLINS, C. C. Sensoryplasticity and tactile image projection(abstract). Investigations in Ophthalmology,1967,6,669.

BACH-y-RITA, P., COLLINS, C. C., WHITE, B.W., SAUNDERS, F., SCADDEN, L., &BLOMBERG, R. A tactile vision substitutionsystem. American Journal ofOptometry, 1969,46,109-111.

BACH-y-RITA, P., COLLINS, C.C., SAUNDERS,F., WHITE, B. W., & SCADDEN, L. Visionsubstitution by tactile image projection. Nature,1969,221,963-964.

BEKESY, G. von. Sensory inhibition. Princeton,N.J.: Princeton University Press, 1967.

COLLINS, C. C. Tactile image projection(abstract). National Symposium on InformationDisplay, 1967,8,290.

GELDARD, F. A. Adventures in tactile literacy.American Psychologist, 1957, 12, 115-124.

GELDARD, F. A. Body English. PsychologyToday, 1968,2,42-47.

GIBSON, J. J. The sensesconsidered as perceptualsystems. Boston: Houghton Mifflin Co., 1966.

HEBB, D. O. Organization ofbehavior. New York:Wiley, 1949.

HUBEL, D. H.. & WIESEL, T. N. Receptive fields,binocular interaction, and functional

architecture in the cat'svisualcortex. IoumalofPhysiology, 1962,160, 106-154.

LETlVIN, J. Y., MATURANA, H. R.,McCULLOCK, W. S., & PIlTS, W. H. What thefrog's eye tells the frog's brain. Proceedings ofthe Institute of Radio Engineers, 1959, 47,194(H95 1.

LINVILLE, J. G., & BLISS, J. C. A directtranslation reading aid for the blind.Proceedings of the Institute of Electrical &Electronics Engineers, 1966,54,40-51.

ROBERTS, L. G. Machine perception ofthree-dimensional solids. Technical ReportNo. 315, 1963, Lincoln Laboratory, M.LT.,Cambridge, Massachusetts.

SAUNDERS, F. Tactile television: Characteristicsofvisuo-spatial information. Proceedings of theA.F.B. Tactile Display Conference, Palo Alto,Calif., April 1969.

SCADDEN, L. The reception of visual imagesthrough the skin. New Scientist, 1969, 41,677-678.

STARKIEWlCZ, W., & KULIZEWSKI, T. Progressreport on the electroftalm mobility aid.Proceedings of the Rotterdam MobilityResearch Conference. New York: AmericanFoundation for the Blind, 1965.

TAYLOR, J. G. The behavioral basis ofperception. New Haven, Conn.: Yale UniversityPress, 1962.

NOTES1. Supported by DHEW, Social and

Rehabilitation Service Grant No. RD-2444-S;USPHS Research Career AwardNo.5 K3 NB-14,094 to P. Bach-y-Rita; RosenbergFoundation grant; USPHS General ResearchSupport Grant No.5 SOl FR 05566; T. B. WalkerFoundation; and Trust in Memory of Beatrice andJames J. Ingels. We wish to thank Mrs. Betty Hartfor valuable editorial assistance.

2. Address: Smith-Kettlewell Institute ofVisualSciences, Pacific Medical Center, San Francisco,California.

(Accepted for publication May 5, 1969.)

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