Fig. 1 Treated (top) and untreated (bottom) sections of a waterlogged white pineboard (200 to 300 years old) raised from Lake George. The treated section was soakedfor 1 week in 50-percent polyethylene glycol, then air-dried. The untreated section wasair-dried.

-checking was markedly reduced bytreatment, regardless of the duration(4 hours to 7 days). The soaking periodthat will give the desired reduction inshrinkage and checking of the specimendepends on the size of the wood piecesand on the extent of wood decay.The effect of polyethylene glycol

treatment on face checking is clearlyshown in Fig. 1. The top part shows asection of a white pine board that was

soaked for 1 week in 50 percent poly-ethylene glycol and then air dried. Nonoticeable checking occurred duringdrying. The picture at the bottom showsthe severe checking of an adjacent sec-tion that was air-dried from the water-logged condition without treatment.

This study was limited to treatingwood with polyethylene glycol having a

molecular weight of 1000. Wood treatedwith polyethylene glycol-1000 becomesdamp under high moisture conditions(above 80 percent relative humidity)and tends to "bleed" or "sweat" at 90percent relative humidity (3), Polyethy-lene glycol of a molecular weight great-

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er than 1000 may have a slight advan-tage for treatment of wood because itis somewhat less hygroscopic than thatwe used. For wood decayed to the ex-tent that it is difficult to handle with-out crumbling, polyethylene glycol of ahigher molecular weight may also havethe advantage of imparting greater ri-gidity to the wood. The reduced solubil-ity of polyethylene glycol with a highermolecular weight can easily be over-come by a moderate increase in tem-perature.

Processing of the actual bateaux was

started in the field in the summer of1961. The bateaux were kept under wetsawdust during the winter of 1960-61.A wooden tank big enough to containthe largest section of a bateau was con-structed and lined with a sheet of poly-ethylene. Polyethylene glycol-1000 ina 50-percent aqueous solution was usedfor treatment. Half sections and plankswere soaked for 3 days and then re-moved for drying. In over 3 months'drying time a minimum of hair-like sur-

face cracks developed. The wood re-

mained slightly damp to the touch, buthas become firmer and is less suscep-tible to damage than it was when it wasremoved from the water. No shrinkingor change of shape is apparent.The treatment thus proved to be very

valuable. Before treatment, these ba-teaux had to be handled with utmostcare and constantly supported through-out their. length and breadth. Slightpressure caused compression and sub-sequent collapse of cells. After treat-ment, however, it is now possible tohandle these craft and reconstruct theirlines.

RAY M. SEBORGForest Products Laboratory, U.S.Forest Service, Madison 5, Wisconsin

ROBERT BRUCE INVERARITYAdirondack Museum,Blue Mountain Lake, New York

References and Notes

1. A. M. Rosenquist, "The stabilization of woodfound in the Viking ship of Oseberg," Con-servation 4, 13 (1959); R. M. Organ, "Car-bowax and other materials in the trpatmentof waterlogged Paleolithic wood." ibid. 4,96 (1959); H. J. Plenderleith, The Conserva-tion of Antiquities and Works of Art (OxfordUniv. Press, London, 1957); B. B. Christen-sen, Om Konservening of Mosefundne Trae-genstande (National Museum, Copenhagen,1952); A. Stromberg, "Konservering av vat-tendrlnkt tra," F6veningen Sverlges Slofartmuseum I Stockholm arsbok (1957-58), pp.47-60. Muller-Beck, Hansjirgen, A. Hass,"A method for wood preservation usingArigal C," Conservation 5, 150 (1960), Frenchsummary; S. Augusti, "The conservationtreatment of some excavated wooden objects"("Traitement de conservation de quelques ob-jects de foville en bois"), translation No. 435,Research Information Service, Division ofPergamon International Cooperation (1961),pp. 1-5.

2. Laboratory experiments were conducted withmaterial supplied by Dow Chemical Com-pany to the Forest Products Laboratory whilefull-scale conservation was conducted witha contribution of Carbowax 1000, a poly-ethylene glycol product of the Union CarbideCorporation.

3. A. J. Stamm, Forest Prods. J. 6, 201 (1956);9, 375 (1959).

15 December 1961

Acquisition and Extinction of theClassically Conditioned EyelidResponse in the Albino Rabbit

Abstract. Comparisons of the perform-ance curve of a classical conditioninggroup with the curves of control groupsprovided unequivocal evidence that elici-tation of eyelid responses to the condi-tioned stimulus was acquired by associa-tions formed between the conditionedstimulus and the unconditioned stimulus.

The eyelid reflex elicited by stimula-tion of the cornea is a prompt, stableresponse which does not appear toshow qualitative variations in differentmammals (1). Nevertheless, the litera-

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ture on eyelid conditioning containsfew references to infrahuman species(2) and none on the rabbit. Yet thealbino rabbit, because of its docility,large eyelid, and low spontaneous blinkrate appears to be particularly suited forclassical studies of eyelid conditioning.

The conditioning apparatus we em-ployed has been described in detail(3), but it was modified for the presentstudy to accommodate rabbits. In theexperimental sessions the rabbit wasrestrained within a Plexiglas box 9inches long, 4 inches wide, and 8 incheshigh. Gross head movements were re-duced by placing the rabbit's headthrough an adjustable stock comprisingthe front of the box and by placingrestraining straps above the snout andacross the head. Positioned 9 inches infront of the rabbit was a 6-inch speak-er and a rod supporting an air jet andspring-return potentiometer. A silkthread was attached to a rod mechani-cally coupled at 90 degrees to the shaftof the potentiometer; and a Velcro tabconnected to the other end of the silkthread was attached to the rabbit's rightupper eyelid by meshing with a per-manently set Velcro countertab gluedto the upper lid. The signal from thepotentiometer, generated by movementof the eyelid, was amplified and thenrecorded by an inkwriting penmotor.Electronic timers controlled the dura-tion of the conditioned stimulus (600msec) and unconditioned stimulus (100msec), and the interval between thesestimuli (500 msec). The conditionedstimulus (CS) was an 800-cy/sec toneof 72 db SPL, and the unconditionedstimulus (UCS) was an 80-mm puffof compressed nitrogen delivered to thedorsal region of the right cornea. Toinsure continual exposure of the cornea,the rabbit's right lower eyelid was tapedopen.

Forty albino rabbits, 85 to 90 daysof age, were assigned to one of fourgroups for 8 days of acquisition train-ing and 3 days of experimental extinc-tion. In acquisition, one control groupreceived the CS alone (group CS-A),another received the UCS alone (groupUCS-A), and a third control group(group R) received random presenta-tions of the CS alone (CS-R) and theUCS alone (UCS-R). The fourth group(group CS-UCS) was the classical con-ditioning group and received pairedpresentations of the CS and UCS at aCS-UCS interval of 500 msec. GroupsCS-UCS, CS-A, and UCS-A consistedof 12, 10, and 10 rabbits, respectively,18 MAY 1962

and received 82 acquisition trials perday at randomized intertrial intervalsof 15, 20, and 25 seconds (mean 20seconds). Group R consisted of eightrabbits and received 82 CS alone and82 UCS alone trials. The randompresentation of CS alone and UCSalone trials was restricted within twotrial blocks, and the intertrial intervalswere randomized at 5, 10, and 15 sec-onds (mean I'DOeconds). In extinction,all groups received 82 CS alone trialsper day at randomized intertrial inter-vals of 15, 20, and 25 seconds (average20 seconds).

In acquisition all eyelid closures of at'least 1-mm deflection from the base-line were recorded from 0 to 525 msecafter initiation of the trial. In extinc-tion the interval was extended to 600msec. Figure I presents the results ofplotting percentage of responses forgroup CS-UCS in acquisition and ex-tinction. Multiple t-test comparisons ofmean percentage of responses amongthe control groups revealed no signifi-cant differences in acquisition or ex-tinction; and their performance curvesare presented collectively in Fig. I byhash lines indicating the upper bound-ary of percentage of responses. Thepercentage of acquisition responsesamong the control conditions did notincrease over days, and never exceededa 4.5 percent level of responding ex-hibited by the UCS-R condition onday 3. In contrast, group CS-UCSdemonstrated a steady increase in per-

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centage of conditioned responses andattained a level of 71 percent on day8. Although the function is S-shaped,there is little evidence that asymptoticperformance had been attained. A t-testcomparison of mean percentage condi-tioned responses of group CS-UCS on

day 1 and day 8 was highly significant(P < .001); and an analysis of trendrevealed a significant linear (P < .01)and cubic component (P < .05). Thesignificant linear trend indicates thatthe percentage of conditioned responsesincreased over days, and the significantcubic trend indicates that the S-shapedfunction was reliable. In extinction, themean percentage of conditioned re-

sponses in group CS-UCS went from36 percent on block 1 to 9 percent onblock 6; whereas, among the controlgroups, the mean percentage of re-

sponses never exceeded 0.5 percent on

any block of trials.The major purpose of our study was

to investigate the possibility of classi-cally conditioning the eyelid response inthe rabbit. The performance curves inFig. 1 indicate that the course of ac-

quisition and extinction of responses ingroup CS-UCS cannot be attributed tochanges in spontaneous blink frequen-cy resulting from UCS presentations(group UCS-A), pseudoconditioning orsensitization (condition CS-R of groupR), or alpha (reflex) responses elicitedto the CS (group CS-A). Consequently,unequivocal evidence has been pro-vided to indicate that elicitation of eye-

.-.-o CS-UCS(CS-AI CS - A

UCS -R

U)CS-R

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10

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1 2 3 4 5BLOCKS

6OF

7TRIALS

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Fig. 1. Mean percentage of responses plotted in 82 trial blocks41 trial blocks during extinction.

1 2 3 4 5 6

during acquisition and

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lid responses to the CS by group CS-UCS had been acquired by associationsformed between the CS and UCS (4).

NEIL SCHNEIDERMANISRAEL FUENTES

I. GORMEZANODepartment of Psychology,Indiana University, Bloomington

References and Notes

1. H. Strughold, Am. J. Physiol. 94, 235 (1930).2. E. R. Hilgard and D. G. Marquis, J. Comp.

Psychol. 19, 29 (1935); , Psychol. Mono-graphs 47, No. 212, 186 (1936); B. Hughes andH. J. Schlosberg, J. Exptl. Psychol. 23, 641(1938).

3. J. W. Moore and I. Gormezano, J. Exptl.Psychol., in press.

4. The study was supported by NSF grant G-16030.

24 November 1961

Countercurrent Streaming inLiquid Surfaces and Its Relevanceto Protoplasmic Movements

Abstract. Movements of surface filmscounter to the interior stream are broughtabout by film pressure generated by sur-face tension gradients. In a similar process,the formation of new interfaces duringprotoplasmic syntheses could sustain gra-dients of interfacial tension with resultingprotoplasmic movements.

Biologists are familiar with move-ments of contiguous protoplasmic con-stituents in opposite directions (1).Some simple but fascinating hydro-dynamic systems that produce similareffects and may have a general bearingon protoplasmic movements are pre-sented in this report.

If a propulsive mechanism is as-sumed at some region along the longi-tudinal axis of a closed, fluid-filledsystem, a flow pattern like that depictedin Fig. 1(a) follows from the continuityequation. Similar flow patterns, "foun-tain streaming," have been observed inamebas (2). Such patterns of flow canalso occur in essentially open systems.The surface forces that are responsiblecan produce an amazing diversity ofphenomena but have received little re-cent notice in connection with biolog-ical problems.Working models are produced by al-

lowing a stream of water from a nozzleto flow down an inclined plane into avessel. As long as the stream flowswithout obstruction and runs off thebottom edge of the plane, the flow re-mains essentially unidirectional (Fig.1, b). However, when fluid accumulatesin a pool at the edge, or when thestream emerges directly into the water

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in the vessel, separation of flow andbackflow of the peripheral surfaces oc-curs. A countercurrent circulation withsharp boundaries of flow separation isinitiated (Fig. 1, c). Peripheral surfacefilm is transferred centrally by con-vergence at the upper boundaries ofthe vortices. Central surface film eitherreenters the peripheral streams at theregion of emergence over the static bodyof water, or returns aftef traveling outover the water. A large portion of thesurface can become involved in thecirculation.

These surface movements are readilyvisualized with powdered charcoal. Par-ticles at the surface are seen to flow inopposite directions along adjacent paths,as indicated in rough schematic out-line in Fig. 1 (c, d, e, f, g). If an outerloop (or a network) is created at theperiphery, surface film travels out intothe loop and rejoins the main circu-lation upstream (Fig. 1, f). But theloop stream itself travels in the op-posite direction and joins- the main-stream downstream. When particulatematter moving downstream in the in-terior is viewed through the counter-moving surface film, also carryingparticulate matter, particles moving inopposite directions seem to be threadingtheir way between one another. Thesame impression is gained on micro-scopic examination of countermovingparticulate matter in protoplasm, wheredepth of focus permits simultaneousviewing of particles both at and be-tween interfaces.

If aplates,limited

stream is confined between twothe vortical circulations areto the menisci but are greatly

accentuated. Even at relatively highflow rates, countermoving peripheralsurface film travels from distant regionsto the nozzle. Surface particles trans-fer to the interior at points where themeniscal film is broken. Sometimes theybecome trapped between the counter-flowing surface films, where they spinlike tops.

These effects occur over a wide rangeof flow rates and also take place onhorizontal surfaces. A leisurely counter-current streaming has been set up ina narrow, almost horizontal, stream 15inches long; convergence of peripheralsurface film into the mainstream tendsto occur in regions where an apprecia-ble velocity gradient is created by nar-

rowing of the stream, or obstructionscause the peripheral flow to deviatecentrally.

These phenomena do not depend onthe presence of particulate matter orgas-liquid interfaces. Vortical surfacecirculations occur to some degree evenin double glass-distilled water, on thesurface of which camphor will "dance"actively; bits of dust reveal the exist-ence of the circulations. Patterns ofmovement in water are influenced byrate of flow, extent of the wetted area,obstructions (Fig. 1, A), and other fac-tors. The lower the surface tension andslower the flow, the greater the dis-tance over which countercurrent stream-ing occurs.

It seems clear that the forces re-

sponsible for counter movement of sur-face film in these systems are trans-mitted longitudinally within the film.Since this cannot take place in the sur-face of pure water (3), the phenomenon

a

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Fig. 1. Models of countercurrent streaming. In b, c, d, e, f, and g the dashed baseline represents the edge of the inclined plane and (in c, d, e, f, and g) the waterlevel in the vessel. The pattern of e occurs either at a greater flow rate or smaller sur-face tension gradient than that of d. A speck of detergent, by lowering the surfacetension and increasing the surface tension gradient, converts the circulation of e tothat of d.

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