Magnetic Tape Recording in the Teaching of Histopathology

Brit. 3. med. Educ., 1968~2, 283-292

Magnetic Tape Recording in the Teaching of Histopathology" STEWART FLETCHER and ALAN A. WATSON University of Edinburgh and University of Glasgow

The application of tape recordings which we are going to describe is one of the most straightforward. It is simply to provide a commentary to guide the listener in his examination of histopathological specimens, both naked eye and with the microscope. We show how our need for the recorded commentaries arose, what their advantages are, and how they may be composed and recorded.

The use of tape recordings in medical education is described in the proceedings of two conferences, (Graves and Graves, 1963 and 1967) and in the monograph of Graves and Graves (1965). The system of tape recording is internationally standardized so that tapes can be recorded and played back by widely separated users. Several bodies have taken advantage of the ease with which they can be exchanged, notably the Medical Recording Service of the College of General Practitioners whose tape lending library is available to doctors for private or group listening. The tape recordings available include talks or lecrures, often by distinguished contributors, and many are accompanied by sets of 35 mm transparencies which the listener can project when requested by the recording. In a more refined method (Harden, 1968; Harden and Wayne, 1968; Harden, Wayne, and Donald, 1968)~ the changing of the transparencies is itself tape- commanded and depends upon the use of a dual- track recording system. One track carries the commentary and the other an accurately cued signal which is used to operate the changing mechanism of a 35 mm casette-loading projector. The synchronized tape-transparency system has been used successfully in medical teaching and many students and teachers prefer it to 8 mm or even 16 mm sound cine film for certain topics. Close study of the projected image of the 35 mm transparency is aided by crisp focus, excellent detail, and absolute steadiness. Sound reproduction,

+Based on a paper and demonstration presented to the Pathological Society Meeting, London, January 5, 1968.

too, is much better than with cinC and is un- disturbed by projector noise. The system of synchronized tape and transparency is an excellent teaching aid, especially for demonstrating rare specimens or expertly-chosen examples which the student could not normally identify confidently without individual tuition - for example, cell types in haematology or in diagnostic cytology. However, in training histopathologists we believe that there i s no substitute for careful microscopic examination of stained tissue sections. Unfortunate- ly, repeated demonstrations of the same topic to small groups of students or postgraduates make heavy demands on staff. On the other hand, histological study aided only by books requires a fatiguing and distracting alternation between the microscope and a text not specially created for the sections under examination. A tape-recorded commentary can overcome those difficulties and has proved to be an agreeable way of learning, with several advantages beyond its use as a mere substitute for a teacher. Unlike commentaries for synchronized 35 mm transparencies which merely describe fked views, those for histological instruction must guide the student with certainty from one feature of the section to the next. T o do so effectively requires certain verbal and other devices, which will be discussed.

The Need for Tape Recordings in Teaching Histopathology

Our interest in the method grew up because one of us (A.A.W.) had to give repeated tuition in gynae- cological histopathology to final year students and recent postgraduates whose other duties forced their attendance in small numbers at irregular and inconvenient times. We therefore decided to make tape recorded commentaries on the histopathological sections and use them primarily as substitutes for a teacher. Each tape lasted between 20 and 25 minutes and dealt with a single topic - for example, the phases of the normal endometrium. The number

284 Stewart Fletcher and Alan A. Watson

of slides which could be studied microscopically in this way was from four to six. The commentary began by announcing the topic and after a brief introduction guided the student’s examination of each slide in turn, beginning with the naked eye appearances. Thereafter directions were given for orienting the slide correctly on the microscope stage and the listener was led through an orderly microscopical examination using successively the scanning, low and high power objectives. Adequate warnings of impending lens changes were given and a pause was always introduced to allow them to be carried out, the lens refocused and the feature found before the commentary began once more.

To avoid monotony two voices were used, one to announce, give general directions and introduce occasional brief summaries, and the other (the presenter) to deliver the commentary on the sections. The recording techniques necessary to do so are described later. Our aim was to produce and deliver the commentary in a manner sym- pathetic to the average student so that he could follow the directions without falling behind. However, the method does allow the listener to work at his own rate, for, if the pace is found to be too fast, the recorder can be stopped, and if a passage proves too difficult it can be rewound and repeated. For replaying to students, a middle-grade domestic tape recorder was used either with the loudspeaker or headphones. Headphones avoid dis- turbing others, exclude distracting room noises and in our opinion make the method more compelling. With a good commentary it was possible for up to four students to listen to the same recording over the loudspeaker without serious inconvenience from individual requests for stoppage or repetition. Each student was provided with an identical set of slides numbered to correspond with the tape and with a good quality miscroscope. A mechanical stage is essential to the method and a binocular head, preferably with wide-angle eye pieces, is desirable. A suitably shaded bench lamp and a piece of white paper to serve as a background are also useful for the naked-eye examination. For revision purposes, to assist note-taking, and to allow par- ticular passages on the tape to be found readily, copies of the script can also be provided.

When first introduced the adequacy of the medium was gauged by discreet observation of the students’ behaviour. During the commentary we noted any signs of confusion, agitation, or clum- siness in lens changing or other manipulations and marked out typed scripts accordingly to see how they could be improved. At the end of the lesson the students were asked about any special difficulties and their comments were noted. Student responses to the earliest commentaries were en-

couraging and we decided that the method was worthy of development and improvement.

In practice it was easy to gauge the success of a commentary subjectively. If it is good the student is relaxed, his movements unhurried, and he finds no call to stop the machine. Often he will remark that ‘the time seems to pass quickly’. A bad script results in a harassed, hurried attitude with clumsy changes of lenses, rapid inaccurate focusing, ob- vious confusion, and frequent stops and repetitions. From our early experience we established certain techniques of script writing which we have found helpful in ensuring the correct tempo and clarity of the programmes.

Techniques of Script Writing The producer of a commentary for teaching histopathology has two main responsibilities. One is to help the student to find the different features of the section and the other is to describe their properties and significance. In script writing the purely descriptive passages are straightforward, but guiding the student infallibly from one feature to another can prove difficult especially in a large and complex section. Therefore, in describing the form which our scripts take, we pay special attention to the verbal and other methods used to help feature- finding.

Introduction The scripts always begin with an announcement of the topic, the numbers of the slides to be studied, and the name and department of the presenter. The presenter then begins his commentary with an introduction which explains the clinical, physiolo- gical, or pathological significance of the subject and gives any other necessary general information. The introduction does not call for an examination of the sections and the student simply listens to it while settling himself at the microscope. The introduction is one of the exceptions to a general rule that only demonstrable features of the sections should attract detailed comment. For that reason the introduction, and certain other passages where unillustrated background information is given, are kept as short as possible. Usually each slide is examined first with the naked eye and the intention of doing so must be announced before the identity of the slide is revealed. If the order is reversed and the slide is named first, the student almost always picks it up hastily and mounts it on the microscope. Our usual formula therefore is to say ‘with the naked eye, prepare to examine the first slide’ - followed by a pause. The arrangement of the two phrases in this passage reflects one of the properties of the spoken command: unlike a printed text it is impossible to tell what is coming next. Great care must therefore

Magnetic Tape Recording in the Teaching of Histopathology 285

be taken to tell the listener what to do in a precisely arranged order if errors in slide-handling are to be avoided. Good scripts, in addition, should warn the student what not to do, and point out the common misunderstandings and pitfalls. Potential difficulties often can be overcome by a skilful descriptive approach. The best scripts therefore, are likely to come from experienced teachers of histopathology, especially when they are written soon after demonstrating the topic to a large class. There the experience of correcting a wide range of misconceptions often suggests approaches which can lead to their elimination and yield scripts more in sympathy with student needs. In writing commentaries a good rule is to tell the student from time to time what general form an approaching examination is going to take, for a little prior knowledge of the purpose and direction of t h e study always helps him to follow it more expectantly and confidently.

The histological sections for examination are mounted centrally on 3 in. x I in. slides under a cover glass and each bears a label at one end with its title and number. The solitary label makes the slide asymmetric and when the slide is held with the label on, say, the right-hand side its vertical orientation is assured. The section thus acquires a top and bottom, and a left and right-hand edge which are indispensable as axes of reference in feature finding. In the naked-eye examination the student is acquainted with the orientation and main natural divisions of the specimen. It begins by describing briefly the shape, size, and staining characteristics of the section, mentions the presence of any indelible markings made to assist the examination, and identifies one or two easily recognizable features - for example, a mucosal or epidermal surface. Thereafter the various layers are identified in turn - for instance, submucosa, muscularis, and serosa - making use of their position and staining properties to distinguish them. Having established the normal arrangement of the tissues, abnormal findings, such as rumours, are pointed out by reference to their layer and staining properties.

The naked-eye examination should not be neglected: it is as important as the microscopic examination and prepares the listener for it: when carefully described most students are surprised at how much it can reveal.

Microscopic Examination On beginning the microscopic examination certain precautions are needed. With rare exceptions, the microscope inverts the image of the specimen on its stage. Therefore, if the section has been examined naked eye with its label on the tight-hand side it must be arranged on the stage of the microscope

D

with its label on the left-hand side. Perhaps the most foolproof verbal formula is to introduce the microscopic examination by saying ‘Now turn the slide so that its label is on the left-hand side. (Pause). Keeping it in that position secure it to the stage of the microscope (Pause). When you have done so, select the scanning objective and bring it into focus (Pause). Now check rhat the basophilic mucosal surface appears at the uppermosr margin of the section (Pause). If it does not, stop the recording until you have rearranged the slide’. (Pause).

Plenty of time should be given to gain familiarity with the appearances under the scanning objective as it makes subsequent feature-finding with the higher power much easier. All the main features should be outlined at this stage before each in turn is studied in greater detail.

Under the microscope, feature-finding can be greatly assisted by indelible ink marks on the coverslip. The technique of making them is described later. They take the form of dots to draw attention to adjacent structures, pairs or sets of lines to isolate segments of an edge or mucosal surface, and circles to surround areas of tissue. Fine lines are sometimes useful to link two or more circles in sequence and, provided they do not obscure the section too much, make feature-finding almost infallible. Different colours of indelible ink can be used where several spots are needed but too many are undesirable and the number can often be reduced by skilful placing and scripting. Thus a single spot placed between two structures serves to identify either when qualified by simple directional terms - left, right, above, below.

The microscopic examination should be unhurried. The student should be put at his ease by the tempo of the commentary and by the wording of the directions - for example, ‘Move slowly along the mucosal border from left to right’ encourages relaxation right at the start. Smoothly progressive slide movements can be ensured, and errors elimi- nated by taking advantage of the natural contiguity of structures. Sections are commonly made up of several layers. The most superficial, for instance the mucosa, can be examined from left to right: at its right-hand edge the underlying layer can be found readily and d e d slowly from right to left and so on till all the layers have been studied. When describing several features on the periphery of a section they should be pointed out in a regular circular sequence never in a series of hasty zig-zag movements across the diameter of the section.

Studying Details To study a feature in greater detail with the higher powers the presenter iirst guides the student to it under the scanning objective. Once found he directs

286 Srewart Fletcher and Alan A. Watson

‘Change now to the low power objective’ followed by a pause long enough to allow the condenser top lens to be swung out and the objective to be changed and re-focused - all on an instrument which may be unfamiliar to the user. After the low power description has been completed the high power examination is approached in a similar way. The most important general rule for the use of lenses is that the time spent using a lens should justify the time needed to select it and re-adjust the instrument. Rapid glimpses with one power before moving on to the next are very harassing to the student and can be avoided by careful planning. It is sometimes better to ‘use the low and high powers freely’. The student can then select whichever lens on his microscope suits him best and the writer’s task is made rather easier. Specific lens-changing directions are no longer required and the commentary becomes more applicable to microscopes whose lenses have different magnifications from those used in the preparation of the script. Indeed, it is always useful to quote (for instance, on the label of the tape box) the overall magnifications for which the commentary has been written. If wide-field oculars have been used, the exact eyepiece and objective combinations are best stated. Sometimes, it is possible to omit the low-power examination and go straight from the scanner to the high power. When doing so a little extra time should be allowed to find the feature again, for, sometimes, the objective fields are far from concentric.

The script-writer should be aware of the normal reactions of the listener to different aspects of the microscopical examination so that he can adopt the correct style and tempo in his recording. For example, during feature-finding the listener requires greatest concentration and may be prone to some diffidence and anxiety. Great care must therefore be taken to give orderly, clear instructions at a rather slow tempo relieved by adequate pauses. TO avoid distraction from the search, information not strictly relevant to it must be excluded ruth- lessly. However, on finding a feature with certainty the student becomes more relaxed. Therefore, immediately after leading him to a histological structure it is considerate to mention one or two of its readily observable characteristics : the success of his efforts confirmed, the listener can then continue completely at his ease.

Once found, the detailed description of a feature under the low and high power objectives gives little difficulty to the student: the presenter can now increase the tempo of his commentary and during the spells of easy histological examination he can weave into the script brief comments on the functional, clinical, embryological, or pathological significance of the tissues.

Because each specimen presents unique difficulties the account of script-writing describes our solutions only to the major problems shared by all. Every script must be written at the microscope while examining the sections, and, in checking the adequacy of each passage in the draft for clarity and effective use of the voice, a small office dictation machine is indispensable. T o make the effort of writing a script worthwhile the number of identical sections available should be adequate, which may mean allowing a margin of 50% for increased use and breakages. If large classes are to be taught by the method described later in ‘Teaching a Large Class’ it is important to examine each one separately to ensure that the features mentioned in the tape are present in each of them. When differences in a large batch of sections are unavoidable the script must be directed at the one where the features are least in number and poorest in quality. When providing large numbers of sections it is unwise to waste time on a search for the ideal block which shows all the features of a condition in one section. The topic can be taught better in stages, the first section showing the common basic appearances and those which follow selected only for the quality of individual rare features. Sections not available in quantity are best avoided since losses and breakages might very soon render a painstakingly prepared recording valueless. It is important also not to attempt to apply tape teaching to unsuitable specimens, especially those which defeat feature-finding - for example, blood, bone marrow or cervical smears, where the cells are so subtly different that they cannot be recognized from their description, and are so small that marking is scarcely practicable.

When the microscopic examination of each slide comes to an end the announcer reads a short summary of its appearances. Some students merely listen to the summary, others like to make a few notes, while others use the microscope freely to remind them of the main features of the section as they are mentioned. We give no advice on the student’s attitude to the summary and leave him to do as he pleases. When it is over, however, it is wise to request that ‘the microscope should be left with the scanning objective selected, ready for the next examination’.

At the end of the tape we either give a short general summary of the topic or sometimes gather together the summaries of the individual slides and so provide a good opportunity for note-taking. The commentary closes with an announcement which acknowledges the presenter and finally reminds the student to switch off the equipment, see that the scanning objective is selected, and replace the dust covers.


Advantages of Tape-recorded Commentaries

In learning a practical skill which employs the eyes and hands fully it is unquestionably easier and quicker to be told by someone how to do it than to turn constantly to a text. The voice enjoys the advantage over print of the property of modulation - ‘the correct and artistic use of pitch, pace, pause, phrasing, inflexion, tonal amount and quality’ (Marash, 1962). It is therefore better able to emphasize the important, to dispense with the trivial and to add, even to the dullest topic, such attractive qualities as discovery, satisfaction, and even excitement. What Lord Birkett (1961) has called ‘the art of attractive and persuasive speech on all occasions that call for its exercise’ has a bibliography of its own, but the little work by Marash (1962) and the more comprehensive treatment of Black and Moore (1955) may be recommended.

A histological examination, where the eyes are entirely occupied by the microscopic field and both hands are needed to control the instrument and specimen, is a good example of the kind of learning to which audible instruction is peculiarly suited. Indeed it has been used for years in the traditional practical class. There the lecturer begins with a short clinical introduction to the specimen, followed by a systematic description which the students try to follow under their microscopes. Provided the teacher is skilled, and there are sufficient demonstra- tors to deal with the students’ problems, it is a justifiably popular method, for it is flexible, in- formal, spontaneous, and secures answers to highly individual questions. Although our recorded commentaries were originally produced merely as substitutes for such teaching, they soon proved to have certain advantages of their own and to have wider applications than we at f is t expected.

I. Improved Accuracy and Clarity of Description Contrary to our experience in conventional classroom teaching, students taught by tape recordings had few or no questions to ask at the end of the commentary - almost certainly because the method both demands and allows a more careful preparation and a more accurate description of the sections. Its advantages are therefore greatest for teachers who become obscure or inarticulate in front of a class. It enables them to prepare, at leisure, highly polished scripts which can be read confidently before the microphone to yield recordings which are far better than their usual performance. Indeed, the work of preparing scripts can do much to help junior teachers in their classroom delivery, for it forces them to think carefully about the topics and

to make a planned, orderly, and clear approach to the study of the sections.

From the students’ point of view also, the teaching is likely to be better, for the close linkage of sound and vision makes it easy for him to expose bad description: the presenter must tell exactly what can be seen and not merely utter unverifiable quotations from faulty textbook accounts.

2. Standardization and Improvement of Wstological Examination The need for an accurate script allows the content of the commentaries to be considered and edited by a panel of teachers and agreed approaches to the topic adopted. Contradictions between teachers can be Iessened and free access to the tapes and scripts lets every ’member of staff know the exact nature of the histological teaching. The method not only teaches the facts of histology, but frequent listening to tapes with a standardized approach breeds orderly and systematic habits of naked-eye and microscopic examination. It is also valuable for establishing standard criteria and nomenclature among wide- spread collaborators in histological research - for example in national surveys which involve the grading of tumours or the staging of premalignancy by workers in different laboratories.

3. Ease of Revision and Editing Once made, the alterations needed to keep the recording up to date or remove imperfections revealed by use require little effort. After an amended script has been prepared, it can be recorded again without great difficulty. Often, however, less drastic treatment is called for and small passages can be revised by simply cutting them out of the tape. They are then re-written and recorded and the new length of tape is spliced into the original. The same technique may be used to correct m i s - takes during a recording session. The presenter simply reads the section again correctly, the faulty one is cut out later, and the continuity of the tape restored by splicing. Mistakes not noticed by the presenter during recording may be noted by the monitor, marked on a copy of the script and re- read at the end of the recording. They are then cut out and spliced into the master tape in place of the original.

4. Active Participation is Retained Although the commentary makes the learning pro- cess easier, the student is still actively engaged in the manipulation of the microscope and in the search for features. Active participation prevents his attention from wandering, as it may do with the entirely passive forms of audio-visual aid: it is a

288 Stewart Fletcher and Alan A. Watson

very compelling way of teaching and most students find the encouragement which it gives to their own efforts satisfying.

5. Setting up a Reference Library In time both the collection of tapes and the number of users increases, and for private study or revision by members of a large class it is advisable to set up the service in the pathological museum where it can be used freely at any time. A bench is made available bearing an indexed collection of tapes and slides and several listening units, each equipped with bench lamp, microscope, tape recorder, and earphones. When it is much used by undergraduates damage to the equipment may be expected. One of us (S.F.) has produced a video-tape for use with closed-circuit television which tells new users how to thread the tapes and use the recorder and microscope properly. The most serious damage would be complete or partial loss of the commentary. We therefore issue only copies of the master tape for student use and prevent their accidental erasure by blanking-off the ‘record’ key with a plastic guard. Most domestic tape recorders have foolproof tape transport systems and physical stretching or tearing of the tape by inept handling is very rare.

However, should damage to the recorders or tape collection still be feared a solution is to house them behind the counter of the students’ library in charge of the assistants. Each recorder is then connected by lines to a correspondingly-numbered listening unit at a table reserved for microscopy. One line carries the output from the recorder to the listening unit where it is connected to an earphone socket provided with a volume control. Another line is connected to a remote control foot switch which the student can use to start, stop, and rewind the tape. Remote control facilities are provided as standard on certain makes of machines. To use the service the student is given the set of slides at the counter and is then directed to a vacant numbered listening unit. Meanwhile the library assistant switches on the appropriate recorder and threads the tape on to it. Control thereafter is entirely from the student’s footswitch. By the use of vertical rack mounting, six machines together with a few shelves for the tape collection need take up little room and they allow six students to hear different tapes simultaneously.

If there is no suitable library accommodation, the equipment just described can be connected by lines between physically separate parts of the building. The onIy additional equipment needed is a telephone to allow students at the listening bench to request the commentaries from some con- tinually manned office or laboratory where the staff can look after the recorder and set up the tapes.

6. Setting up a Lending Library Since recordings are readily interchanged it is possible to run a postal library service for the bene- fit of postgraduate students of histopathology in laboratories far from the main teaching centres. It is esssential that an internationally standardized system of recording be employed and the problem of compatibility between recording and reproducing equipment is discussed later. A lending service such as that contemplated by the Education Committee of the Association of Clinical Pathologists (Pugh, 1968) could do much to propagate high standards of histopathological training among postgraduate students who have access to a tape recorder. Perhaps the greatest contribution which the method can make is to the training of medical students and postgraduates in under-developed countries where well-qualified teachers may be scarce. Tape recordings afford a unique opportunity for overseas students to hear an expert describe his own slide collection. The personal nature of the commentary and the authenticity of the specimens combine to give an understanding of histology which even the best photographs and textbooks cannot convey. For under-developed countries tapes and slides would probably be donated rather than lent and hence facilities for tape copying and slide preparation on a fairly large scale should be considered when setting up a lending library.

Professor K. R. Hill (1968) has suggested an ingenious way of solving language difficulties in overseas teaching. The tape is, sent out with thecomment- ary recorded in the usual way on the upper half-track as is described in the section ‘Compatibility of Equipment’. A copy of the script is provided also and is translated by the recipients into their own language and then recorded on the lower half track of the tape by the use of a recorder with independent dual channels. The resulting tape, if played back on a dual-channel machine, allows the listener to hear the whole or parts of the commentary in either language by simply operating the track selector switch.

Tapes can be sent by air-mail at the inexpensive ‘small-packet’ rate (Her Majesty’s Stationery Office, 1967), which allows the enclosure of both scripts and slides provided that the tapes are confined to ‘non-current’ material - that is, contain no news or correspondence. If ‘current material’ is recorded the tapes must be sent by the slightly dearer ‘Phonopost’ service which strictly excludes enclosures of any kind other than instructions for their reproduction.

7. Teaching a Large Class The original method, designed to teach individuals or small groups, is not suited to teaching large


classes by headphones or loudspeakers, because when the number of listeners is large so is their range of aptitude. Some would be bound to fall behind seriously, especially those with language difficulties, and the option of stopping and replaying the tape cannot be extended to the individual in the interests of the majority. Since it would be far too costly and time-consuming to provide a separate recorder and copy of the master tape for each student we propose an inexpensive way of providing a reasonable measure of optional

switch immediately to channel 2 to hear the pre- vious 30 seconds of the commentary. They remain on channel 2 until their next difficulty when they can switch to channel 3 for a repetition. Provided the scripts are well presented and short, two opportunities to repeat passages should be adequate for the slower students.

We are indebted to Dr A. A. Shivas who has suggested that, instead of staggered versions of the same commentary, the multichannel system could also be used to play tapes describing the same slides

Ch.l THREE CHANNEL WIRING THROUGHOUT CLASS - T T

t

Ch.3 I TAPE RECORDERS

Fig. I. Optional replay system for the class-room progressively delayed.

replay. Our system is shown in Fig. I. The whole class is made up of listening units which are wired in parallel to three separate channels I, 2, and 3. By means of a three-way selector switch A the student can listen to any channel via the volume control B through his head-phones which are plugged into socket C. Each channel carries the output from one of the three tape recorders, which all play identical copies of the master tape but are startcd at different times so that the commentaries reccived on channels 2 and 3 are, say, 30 seconds and 60 seconds behind that heard on channel I. SN- dents normally begin by listening to channel I and if they fall behind or misunderstand a passage they

using three charnels to carry the same commentary

but delivered at different tempos to suit the slow and fast students.

The provision of three channels in the classroom also has advantages for revision purposes : where the students are already familiar with the commentaries the facility for repetition is scarcely needed and the channels can be used for three different commentaries which may be freely selected.

Techniques: Microscopic and Recording Microscopic Techniques Microscopical preparations were made in the usual way. Marking the cover glasses accurately and

290 Stewart Fletcher and Alan A . Watson

indelibly can be difficult and we therefore describe a method found useful. It is a rather indirect approach which allows the dots to be placed accurately, avoids trial and error with indelible ink, and provides the clean glass surface needed for permanence. The feature is first centred under the appropriate objective and a dot is made beside it on the cover glass with a fibre-tipped pen carrying an easily removable ink of light colour - for example, red. Marking can sometimes be watched directly under the microscope, but if the clearance under the objective is too small or its power dis- turbingly high, it is easier to rack the nose-piece out of the way and do it with the naked eye. The feature can still be pin-pointed by a brilliant narrow beam of light obtained by increasing the intensity of the lamp, stopping down the field diaphragm, and focusing the condenser. A mark can then be made on the coverslip at the point where the fibre tip enters the circle of light and becomes brightly transilluminated. The position of the dot is next checked microscopically and, if necessary, altered. The slide is then removed from the stage of the microscope and another dot is made on its rear surface coincident with the first. The dot on the cover glass is now removed with moist tissue and the surface cleaned and polished. Using glass marking ink (Gurr’s Glass Marking Colour) an indelible dot is next made on the cover glass exactly over the one left on the rear of the slide. Its position is checked immediately and, if accurate, it is allowed to dry and the dot on the rear of the slide wiped off.

Techniques of Tape Recording .

a. Equipment Used The success of audio-visual methods depends not only upon fastidious preparation of the script but also on the technical quality of the sound and vision: no pains should be spared in making the best use of the available equipment, however simple it may be.

To make good sound recordings two acoustically separate rooms are needed, one to act as a studio and the other as a control room to house the recording apparatus. The studio must be quiet and free from radio and electrical interference. In and around hospitals we have found interference to be extreme: the equipment picks up strong signals from mobile radios in ambulances and taxis and also from the residents’ call system, and therefore most of our recordings have been made under domestic conditions.

The recording chain which we use consists of a Reslo VRT/L ribbon microphone mounted on a short stand on the presenter’s table, which is equipped with a shallow lectern for the script, a reading lamp, and a small coloured cue lamp which

allows the operator to warn the presenter that recording is imminent or in progress. The low impedance of the microphone (30 fl) allows it to be connected by long cables without appreciable losses or hum induction from the mains. The microphone cable runs to a physically and acoustically separate attic room where the recording machines and monitoring equipment are set up. The recording equipment consists of a four-channel microphone mixer made by one of us (S.F.) whose output is connected to the input of a Reflectograph Model A half-track recorder which has facilities for com- parison monitoring of the signal by loudspeaker both before and after recording. Communication with the study which serves as a studio is by lines which allow the operator to switch on the cue-light and talk to the presenter, either by loudspeaker before the recording, or through headphones during it. By reading the script the operator can often spot errors in the delivery which might escape the presenter and can draw his attention to them immediately.

The advantage of separating the recording equipment acoustically from the presenter are considerable. It allows monitoring over a loudspeaker without ‘howl-round’, isolates the mechanical noise of the machines from the microphone, and allows the presenter to perform alone, which he may well prefer.

When only two people are available to act as presenter and operator it is often easier to make all the announcements and summaries, which require a second voice, at the end of the main presentation. Later they can be transposed by splicing to their appropriate positions. The pauses too can be spliced into the commentary in the form of lengths of ‘silent’ tape - actually recorded in the empty studio as erased tape is often too silent and leads to an abrupt fall in background noise. In addition to the standard master tape, made at

7) in./sec. on the Reflectograph, we usually make another simultaneously at 15 in./sec. on a Brenell mark 5 half-track recorder and keep it until all editing of the master tape has been completed in case of accidental damage, loss, or erasure. When the master tape has been edited, stop foils and leader tapes are spliced onto its ends and the title, date, presenter, and corresponding slide numbers are marked on the matt surface of the leaders and on a label on the spool box. The master tape is then checked against the slide set, any imperfections noted, and improved passages spliced into the tape to replace than if necessary.

The master tape is used only for making copies and is stored in a dry place at an equable tempera- ture away from magnetic fields which may cause partial erasure: the powerful magnetic catches


fitted to the doors of many storage cabinets are the only likely hazard. For student use the master tape is copied by means of a direct lead from the output of the Reflectograph to the input of the Brenell operating at 3% in./sec. half-track. The slower speed used for the copies gives adequate reproduction and is the maximum found on many domestic machines. A variety of machines have been used for playback to students. The Uher 2000, which is a hybrid machine combining the features of a standard tape recorder with remote control and dictation facilities, is used in the Edinburgh department both for general use and playback to postgraduates. Its convenient controls make it useful for checking passages of scripts as they are written at the microscope.

b. Bibliography The topic of tape recording is covered by a wide range of texts. Of the innumerable elementary works the most comprehensive is that by Nijsen (1967), which is, however, confined to the equipment of one maker, A more theoretical approach to the recorder and the choice and matchhg of the related equipment is that of Guy (1961). Medical tape recording, audio-visual work in general and much good advice on presentation and script writing is provided by Graves and Graves (1965) who deliberately keep the technical side fairly simple. A book which describes the working and use of recorders and dwells on its educational applications is that of Tall (1958). AU the books mentioned also cover tape editing methods and, in addition, that by Nisbett (1962) deals with the whole range of techniques and equipment used in sound broad- casting and can be recommended for those seeking information on a fairly elaborate installation. Detailed information on the mechanical and elec- tronic aspect of the tape recorder can be obtained in the work of Haynes (1957).

c. Compatibility of Equipment To permit interchange of tapes it is important to use tape recording equipment which conforms to internationally acceptable standards - for example, British Standard Specification 1568 (British Stan- dards Institution, 1g6o), International Electrotech- nical Commission publication No. 94 (British Standards Institution, 1962). Standard tape speeds are IS, 74, 34, and 18 in. per second. According to whether the recording is made by a magnetic head which extends entirely over the width of the tape or only over a fraction of it, the ‘track configuration’ is called full-, half-, or quarter-track. The lower the speed and the narrower the track the poorer the quality of reproduction, but the greater the economy in tape, for the single remaining half-track, or the three remaining quarter-tracks, can be used for,

other recordings. Accordingly professional studios use full-track machines which can operate at either 15 or 7) h./sec. Semi-professional and high-grade domestic machines use half-track recording heads and allow the use of two or three of the speeds IS, 74, and 32 in./sec. Quarter-track recorders which operate at the same or slower speeds are highly popular on the cheaper domestic market but their track configuration is not recognized by B.S. 1568 (British Standards Institution, 1960).

A narrow-track recording head - for example, quarter-track - can reproduce, with some loss of quality, recordings made by any machine with a wider track - such as half-track. The opposite, however, is not true, for a half-track reproduction head will cover two recorded quarter-tracks and play them back together, one of them in reverse, so that the result is unintelligible. With those facts in mind, we therefore make certain recommendations which do not violate B.S. 1568 and give the best quality of sound consistent with reasonable costs, interchangeability, and the inevitable use of quarter- track domestic machines for replay.

Master Tapes. There is no advantage in using half-track recording, since the material on the second track will be interrupted by editing the first. Professional standards should be adopted and it is noteworthy that despite the trend to lower speeds and narrower tracks two manufacturers (Ferro- graph and Vortexion) have recently introduced full- track versions of semi-professional equipment operating at 15, 74, and 3% in./sec. For the kind of work described 7) in./sec. full track is the ideal combination for master tapes, although half track recordings are satisfactory. For the master recording, standard-play recording tape should be used in preference to the thinner long play because it is easier to cut and splice neatly.

Copies for Student Use and Lending. The highest speed of most domestic machines is 34 in./sec. We therefore recommend that copies be made at 32 in./sec. half-track. Reproduction by quarter-track machines would therefore be possible but quarter- track copies shoqld not be issued: apart from their other previously mentioned disadvantages they imply the carriage of four commentaries, so that when only one is required another three are need- lessly withdrawn from the library. For lending we consider it wise to adopt the same standards as the Sound Library of the College of General Practi- tioners, which uses long-play tape on one of the British Standard spool sizes of 5 in. diameter. Rather more than 800 feet of long-play tape can thus be carried and provides two half tracks each of 45 minutes playing time at 32 in./sec.

In the past decade a number of systems have appeared which do away with the need to thrend

292 Stewart Fletcher and A lan A . Watson

the tapes from one spool to another through the head gap of the machine. Instead, the supply and uptake of the tape is contained in a single plastic casette which can be pushed conveniently into place on the deck of the corresponding make of recorder. Of the numerous designs, alI different and not interchangeable, only one has gained a measure of acceptance by the rapid obsolescence of the others. It is the Compact Casette (Phillips) whose design has been freely offered and accepted by other manufacturers. Although easy to use and fitted with a device to prevent accidental erasure, the slow speed of 1 4 in./sec., the narrow double tracks on a tape only 0.15 in. wide, and the limita- tions of the recorder (which cannot be used for standard spools or tape) lead to inferior sound quality. The system seems to have been designed primarily for reproducing music in situations where discs cannot be used - for example, in cars. The construction of the casette prevents easy access to the tape so that editing and creative recording is impossible and accidents such as breakage or jam- ming of the tape cannot be remedied easily. Al- though they may deserve acknowledgement as standard for popular entertainment it seems virtually impossible that they u ill become internationally acceptable for serious use and we therefore recommend that they be avoided for library work.

Summary The use of tape recorded commentaries to guide the student in the examination of sets of histological sections is described. The verbal and other techniques needed to ensure ,accurate feature-finding are considercd in detail and the techniques of tape recording are outlined and an annotated bibliography given. The method has been found to be an agreeable way of learning and eliminates the tiresome alternation between the microscope and a printed trxt.

Primarily developed to ease the burden of repeated histological tuition to small groups of students, tape-recorded commentaries have several other advantages, which include improved accuracy and clarity of description, active participation by

the student, standardization of histological teaching, and ease of revision and editing.

The establishment of a reference library of tapes and slides for student use is described and, if a standard system of tape recording is used, it may contribute to overseas education by postal loan.

The method may be adapted to the needs of a large class by providing a measure of optional replay to individual members without great expense.

References Birkett, Lord. (1961). The art of advocacy, in Six

Great Advocates. Penguin Books, Harmondsworth. Black, J. W., and Moore, W. E. (1955). Speech: Code,

Meaning, and Communication. McGraw-Hill, New York.

British Standards Institution. (1960). Mqqnetic Tape Sound Recording and Reproduction. British Standards Institution, London. (B.S. 1568: 1960).

British Standards Institution. (I 962). Zntemtional Electrorechnical Commission. (Publication I.E.C. 94). British Standards Institution, London.

Graves, J., and Graves, V. (Ed.). (1963). Conference on the Use of Tape in Medical Teaching. Royal College of General Practitioners, London.

Graves, J., and Graves, V. (1965). Medical Sound Re- cording. Focal Press, London.

Graves, J., and Graves, V. (Ed.). (1967). Second Con- ference on the Use of Audiotape in Medical Teaching. Royal College of General Practitioners, London.

Guy, P. J. (1961). How to Get the Best out of Your Tape Recorder. Norman Price, London.

Harden, R. McG. (1968). Tea hing without teachers. An audio isual method of self-instruction. Scor. med. J. , 13, 206-207.

Harden, R. McG., and Wayne, E. (1968). The Frank- Kindermann audiovisual tutor machine. Med. biol. Ill., In press.

Harden, R. McG., Wayne, E., and Donald, G. (1968). An audiovisual technique for medical teaching. Med. biol. Ill. , 18, 29-32.

Haynes, N. M. (1957). Elements of Magnetic Tape Re- cordinz. Prentice Hall, New York.

Her Majesty’s Stationery Office. (1967). Post Ofice Guide. H.M.S.O., London.

Hill, K. R. (1968). Personal communication. Marash, J. G. (1962). Effective Speaking. (New ed.).

Harrap, London. Nijsen, C. G. (1967). The Tape Recorder. Iliffe, London. Nisbett, A. (1962). The Technique of the Sound Studio.

Focal Press, London. Pugh, R. C. B. (1068). Personal communication. Shrvas, A. A. (1b68). Personal communication. Tall, J. (1958). Techniques of Magnetic Recordzna.

Macmillan, New York.

Documents

Magnetic Tape Recording in the Teaching of Histopathology