Since veterinary schools began over 200 years ago , there have been few advances in the teaching of the three-dimensional structure of animals. There has been a long tradition of killing, preserving, and laborious dissection of animals. Somehow, teachers of veterinary anatomy have lived with the problems of:

• supplying enough animals so that each student gets an adequate experience confronting the ethics of justifying the killing large numbers of animals
  
• disorientation caused by the displacing of body parts from their proper position during dissection, and the destroying of adjacent parts so that certain items can be seen
  
• the rigidity and altered position of the limbs of preserved cadavers from normal
  
• the non-repeatability of the dissection procedure on the same cadaver
  
• the expense, especially for skilled labour, in preserving and maintaining cadavers
  
• the time that dissection takes in the curriculum. These days, less time is available for anatomy teaching as new disciplines demand to be included
  

Dissection is becoming too expensive and too inefficient, as a predominant means of learning about living animals. But there are alternatives:

• Direct use of live animals, complimented by the use of illustrations, video demonstrations or computer graphics. Surprisingly, there are very few books that show how this might be achieved for veterinary anatomy.
  
• Computer simulations that can strip away layers or reveal organs in their correct locations relative to one another in three dimensions.
  
• Interactive use of modern imaging methods such as radiography, fluoroscopy, ultrasound and magnetic resonance imaging, combined with photography and animation. Imaging methods that show the living body in section (tomography). X-ray computed tomography is restricted to transverse sections. Magnetic resonance imaging creates sections in any plane and therefore has more potential.
  

Alone among delivery tools, computers can deliver all kinds of illustrative materials, with the special advantage that they are cheap and already used by students for other purposes. Several programs will be presented that show the wide variety of graphics that can be used, how interactivity creates extra learning opportunities, how learning material is available to students flexibly in their own time and at their own pace, how self-testing is possible at all stages of the learning process, and how student progress can be monitored by the teacher.

Introduction

This title recognises the purpose of preclinical veterinary teaching. Since clinicians treat living animals, it seems desirable that students do a reasonable proportion of their training with animals that are alive rather than dead.
'Depths' in the title is intended to have more than one meaning. Living animals are clinically examined either by eye as though they were transparent, with superficial structures no barrier to deeper understanding, or by the sense of touch as finger tips also sense deep into the body. Successful teaching methods provoke deep learning, and this account tries to be a penetrating, exploring analysis of teaching methods.

Education today is confronted by problems that seem more acute than previously, not least for veterinary anatomy.

• There is a decline in educational funding in most parts of the world. Since human resources are 90% of teaching costs, more students are being taught by fewer teachers and laboratories are not as well staffed. Labour and resource intensive hands-on learning is becoming more difficult to mount.
  
• The use of animals in teaching is coming under increasing scrutiny by animal rightists.
  
• The human-animal bond covers an ever-increasing range of species, even to species as far from being domesticated as stranded whales. Tomorrow's vets will treat some spectacularly peculiar patients, and expect their education to prepare them for these eventualities.
  
• There are many ways to present material, some new and some mediaeval, to teach anatomy. None of them come cheap. Decisions have to be made which depend on some understanding or intuition as to what is best, and how much of each.

Of these problems, only the last is particularly relevant from a pedagogical point of view. The others relate more to ideology, politics and social trends. The way to act seems to be to improve the efficacy, efficiency and ethical value of the teaching methods possible.
Most subjects can use a wide variety of teaching methods. The following list of possibilities shows that this variety is certainly impressive for anatomy.
Dry specimens such as skeletons, individual bones, resin and plaster casts of organs and vessels, plastinations and models are made available to view and handle.

• Wet preparations are stored in tanks for occasional display, or exhibited in museum pots.
  
• Whole animals, fresh or preserved, are dissected by groups of students.
  
• Live animals of suitable disposition are studied to find out what movements are possible, and what features can be palpated.
  
• Problems are set for individuals and groups, generally based on case studies.
  
• Students make peer presentations and perform role plays.
  
• Old and new information technologies range from lecture notes, textbooks, photographs, charts and libraries of books, journals and CD-ROMs, to internet databases.
  
• The passive screen brings graphical displays and sound from slides and audiotape, cinefilm and videotape and, more actively, videodisc.
  
• To radiographic plates are now added an array of imaging methods, including fluoroscopy, computed tomography by Xray and nuclear magnetic resonance.
  
• Finally, virtual reality brings a third dimension to the screen by simulated movement and layering, as well as untold interactivity.

All of these methods are relevant to the education of health professionals in the next millennium, since innovation never seems to completely remove the validity of older methods. As an extreme example of this, mottoes in Latin are inscribed in stone on buildings housing the latest electronic wizardry. But the costs of new or old seldom decline. All need time and skill to prepare and are therefore expensive.

Student access to a wide variety of learning aids surely helps reach the goal of flexible learning. Enter the computer revolution. By bringing graphical images, static or moving, to a computer screen, and taking advantage of animation and simulation, each of the above teaching methods can be delivered on a single machine. Yes, even images and text inscribed in stone. The challenges that the computer age then delivers to educationalists are:

• To make these images realistic.
  
• To create programs that contain all the relevant information in a diverse and flexible way.
  
• To provide the interactivity that will attract and challenge each student to think and therefore deepen the learning experience.

To what extent can we replace tried and true methods? Can computer instruction parallel and enhance other methods that have special advantages? Will computer aided learning eventually be better and cheaper than older methods? Do computers threaten the existence of hallowed halls of learning and the authority of the professors lurking within by their availability, accessibility, and appeal to younger minds?

We are still exploring possibilities. Some examples of these, recently developed in the context of the ideas expressed above, are:

• Toposheep: Basic external landmarks and various stages of dissection of abdominal organs are shown and identified, the parts of the stomach are illustrated down to the microscopic level, and fluoroscopic movies of normal movements of the stomach are provided. Special purpose: to incorporate several modes of graphical display into one method of delivery, and to relate them to the surface of the living animal.
  
• Gracilis the racing greyhound: Emphasis on musculoskeletal anatomy, both general and specific to muscular injury sites. A quiz operates on all identifiable structures. Special purpose: To challenge the student to locate structures of clinical significance in athletic dogs.
  
• Lymph trails: Using photographs of dissections, the flow of lymph from all regions is shown by animation, and the student is quizzed on the location of all lymph nodes in the dog. Special purpose: To compensate for the inability of conventional methods to demonstrate regional lymph flow.
  
• Topocow: All abdominal organs are located in their correct locations three-dimensionally. The student is able to remove or replace organs progressively to show the structures in their positions in the living animal. Special purpose: To overcome problems inherent in dissection, where the location of an organ is only discovered after first disrupting its surroundings, and where reassembly is not an option.
  
• Digital navigator: By moving in several layers within the foot of the horse from skin to skeleton, most structures of clinical significance are presented, along with case studies relevant to these. Radiographs and sonographs are included. Special purpose: To relate all structures to the surface of the horse's foot, and emphasise their significance in clinical diagnosis.
  
• Magnetic resonance images of the pig: Images are accessible in three planes, and can be visualised as an animated series in each of these. Special purpose: To demonstrate possibilities and problems in the sole use of imaging techniques in teaching body structure.
  
• Q on CUE: An interactive quiz designed to use digital graphics of all kinds, including animations and movies. The type of question is flexible enough to include single word answers as well as multiple choice. An explanation is given for each answer. The teacher accesses all student responses and therefore is able to assess both the understanding of students and the merit of the questions. Special purpose: To explore the use of a flexible template in teaching.
  

The computer revolution injects new excitement into teaching. But for the explorers, deep in untracked territory, where are the signposts?