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but go on eating all the grassthey get and much of the cornuntil at last they die, withoutpain.” But Evans believed he hadmicroscopic evidence of a blood-borne pathogen responsible forthe disease.

WIth no facilities for stainingpathogens — an art still in itsinfancy — a temperature of 28oCin the shade and hordes of flies,work with the microscope musthave been exasperating.

However, Evans recalled, “Iwas very anxious to show theliving active microbe to othermedical men, particularly DrCunningham, the surgeon-general in India, and Dr TimothyLewis, the special assistant to theSanitary Commissioner with thegovernment of India, who haddiscovered blood parasites,officially reported and publishedin his illustrated monograph.”

Timothy Lewis, who discovereda trypanosome in the rat in 1879,believed that neither theTrypanosoma lewisi, nor anyother trypanosome, including theone described by Evans waspathogenic. Griffith Evans in hisofficial report did everything topersuade him. He transferred

blood containing parasites fromhorses with the disease, tohorses without symptoms of thedisease whose blood did notcontain parasites. He transferredblood by ingestion and bysubcutaneous injection. And thenhe demonstrated the appearanceof the parasite in the blood of thepreviously healthy horsestogether with the fever and theother signs of the illness. He alsotransferred the parasite to a bitchand through her to her puppy.

At this stage, he was posted toKachar in Assam and he left thepuppy with Lewis andCunningham in the hope that theywould continue his observations.Both were rigidly opposed to thegerm theory.

Evans returned to Britain andretired from the Army in 1895. Hetook a post at the University ofWales at Bangor, renewableannually, until his final retirementin 1910. The honours came late: adistinguished service pension in1913, the Mary Kingsley medal in1917 and the Steel MemorialMedal in 1918. But attention isgrowing to the fact that he wasfully one of the pioneers ofunderstanding infection.

Blood issues: A trypanosome parasite in the blood. Such observations were made byGriffith Evans in the nineteenth century which he linked to disease, but he missed outon early acclaim for his ideas. (Picture: Science Photo Library.)

Q & A

Michael Land Michael Land is Professor ofNeurobiology at Sussex University.He has studied the eyes and visionof a wide variety of animals, andhas written a book, Animal Eyes,with Dan-Eric Nilsson. Morerecently his work has mainly beenconcerned with the relationsbetween human eye movementsand the control of actions.

What got you started inscience? It had to be a lot to dowith the teachers I had at school.The physics and biology teachingwas terrific and the chemistryindifferent. I think this combinationpre-adapted me for looking atthings like the workings of strangeeyes, and away from the molecularbiology that was then excitingothers. At Cambridge I developedan almost Victorian passion forinvertebrates, largely because ofthe superb lectures of Carl Pantin,who managed to combine thetaxonomy, physiology and ecologyof each group in an inspired way.The colossal scale of evolutionbegan to dawn on me too — andthe realization that the vertebratesare only a small corner of the bigpicture.

During the first year of my PhDat University College London I hada stroke of luck. I looked into oneof the 60 eyes of a scallop — theanimal I was working on forreasons unrelated to vision — andsaw an upside down image ofmyself. It dawned on me thatsomething was wrong: the imagewas too bright and, as I waslooking at it through the lens, itshould have been near infinity andnot actually in the eye. The answerturned out to be that this is almostthe only example in nature of aneye that uses a concave mirrorrather than a lens to form animage. My first real ‘aha’ moment.I’ve had three or four since, butthat was the first and the sweetest.

What papers have mostinfluenced you? Different papershave affected me at differentstages in my career. The nice thing

about the comparative work oneyes was that I got to experiencethe beauty of some of the papersfrom the late 19th and early 20thcentury, especially those ofGrenacher and Hesse. The qualityand subtlety of the colouredlithographs in those papers isbreathtaking. They must have costa fortune to produce. Later, as Igot more interested in behaviour, areview by Horst Mittelstaedt‘Control systems of orientation ininsects’ (1962, Annu. Rev. Entom.7, 177-198) introduced a clearframework for thinking about therole of feedback and other systemsideas in the organization ofbehaviour.

My current work on eyemovements was certainly inspiredby one picture in the book byAlfred Yarbus (1967, EyeMovements and Vision. New York;Plenum). The picture is of apainting ‘The Unexpected Visitor’,representing the return of a man toa family, with the eye movementsof a viewer superimposed. Theclever thing Yarbus did was to askhis viewer different questionsabout the picture — for example,“estimate how long the visitor hadbeen away from the family” — andfor each question he got a quitedifferent pattern of eyemovements, each clearly related tothat particular question. This wasthe first clear demonstration thateye movements are not justreflexive movements to prominentfeatures in the surroundings, butare related to the viewer’sthoughts. This seems obvious now,but it wasn’t then.

Why did you switch frominvertebrate eyes to human eyemovements? It wasn’t that muchof a change. I’d worked on eye

movements of spiders, flies andmantis shrimps before, so I wasreally only extending my range ofanimals. Besides, it was nice towork on an animal you couldactually talk to. More seriously,although eye movementrecordings had been made foralmost a century, up until about1990 there was very little work onthe eye movement strategies usedby people doing ordinary things —walking, driving, preparing food,playing games and so on. Therereally wasn’t a Natural History ofeye movements. About that time,wearable eye trackers becameavailable, and there was anobvious niche to fill.

It was interesting coming to thefield from zoology, because eyemovement research had mainlybeen the province ofpsychologists and physiologists,both of whom like theirexperimental conditions to betightly controlled. Experimentalpsychologists in particular aretrained to be fiercely Popperian,removing all confounding variablesand setting up refutablehypotheses. Uncontrolledobservation isn’t an option. Theethological tradition that I camefrom could be experimental, butinvolved minimal disturbance ofeither behaviour or environment.As Niko Tinbergen pointed out, lifethrows up its own experimentalsituations. The trick is to spot theregularities in what at first appearsto be the chaotic continuum ofnatural behaviour. Things have gotbetter recently: psychologists nowapprovingly use the expression‘ecologically valid’ for studies thathave something to do with real life.But for some in funding bodies,‘curiosity driven’ is still anexpression of disapproval. I think itis worth recalling that Darwinspent many years of curiousobservation before coming up withhis big hypothesis.

What is the best advice you’vebeen given? When I was workingat Plymouth on reflectingstructures with the great marinebiologist Eric Denton, we got anice result one day. He said thatwhen you have a good result youshould have a good dinner. Thatway, when you fail to repeat it next

day, at least you’ve had a gooddinner. I also remember J.Z.Young’s dictum — never writeanything you can only publishonce.

Do you have views on thefunding of science? I have alwaysdone ‘small’ science. Bugs andhumans are both cheap, comparedwith cats and monkeys; and I liketo do my own work, or elsecollaborate. So I’m cheap to run. Ithas always struck me as ridiculousthat the process of getting £25Kfor some kit and a little assistanceis as difficult as getting £250K ormore. I have argued that researchcouncils should ring-fence pots ofmoney for different sizes of grant,but I have the feeling that it is seenas just too much trouble toadminister small grants. Being‘good value for money’ in terms ofpapers per pound does not makeyou popular with universitieseither. They just want the overheadthat comes from you becoming alarge employer. As I approachwhat I hope will be an activeretirement the opportunities forfinding the small amounts ofmoney I will need diminish further.Universities had that sort of pettycash once, now they don’t. Itwould be good if someone wouldaddress the needs of wrinklies whowon’t go quietly.

What are the future directionsof your field? I think it notimpossible that within a decade orso we may have a reasonable ideaof what a thought looks like interms of neural activity. No onetechnique can provide this butadvances in scanning technology,single and multi-cellneurophysiology and other moreexotic electrophysiologicaltechniques may crack it. Eyemovements recording can help byproviding observablemanifestations of thoughtprocesses. Modelling may helptoo, but I’ve not been impressedso far. Sherrington imagined thenervous system as an ‘enchantedloom’. It would be good to see hisdream come true.

Department of Biology andEnvironmental Science, University ofSussex, Brighton BN1 9QG, UK.E-mail: m.f.land@sussex.ac.uk

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The author wearing a tool of his trade.