Smoking drums

A DENTIST NEEDS manual dexterity and good powers of observation (amongst many other skills). My PhD supervisor, Robert Harkness, used to teach physiology to the first year (pre-clinical) dental students at University College London. He not only encouraged them to learn the rudiments of the subject but also how to improve their dexterity and skill in observation.

While the students were under Robert’s care, he tried to instil in them something of his spirit of scientific curiosity. Each student had to carry out an investigative project as part of the physiology course. This had to make use of the students’ powers of observation. He felt, quite correctly, that a good physician must be very observant. He had students, with their pencils, watches, and notepads at the ready, measuring, for example, the blink rates of people travelling on the Underground, or how many times a minute peoples’ jaws moved whilst chewing gum, or how often and for how long people scratched their heads. Projects like these, simple though they sound, honed the students’ ability to observe carefully. These projects also helped to instil something else in some of the students: many of them went on to have academic dental careers.

Robert had great manual dexterity and knew that development of this in his students was of great importance to those aspiring to practise dentistry. When he or his wife Margaret was interviewing prospective students, they always enquired whether a candidate played a musical instrument or enjoyed making models or sewing/knitting/embroidery. If they did, then there was a good chance that the candidate’s manual dexterity would be sufficient to perform dental procedures. Robert encouraged this in the practical physiology classes that he arranged for his pre-clinical students. Typical of this was his insistence on the use of the archaic smoked drum kymograph.

Most students doing experiments in physiology would record results from their experimental set-ups, be it a contracting muscle or a stretch of live nerve, on an electrically operated pen and ink tracing that produced a graph on a piece of paper tape. All that was necessary was to plug the measurement transducer out-put lead into the electronic moving chart recorder and wait for the results.

Robert insisted on his dental students using a kymograph with smoked paper, a mechanical predecessor of the modern electronic equipment. A sheet of white paper had to be attached around the outside of a metal cylinder (drum). This had to be rotated carefully above a smoky flame until the entire surface of the paper had been uniformly blackened by a thin layer of charcoal particles. Without disturbing this fragile black layer with a stray finger or thumb, the smoked drum had to be carefully attached to the vertical spindle that emerged from a cylindrical motor. The experimental tissue – often the students measured the contraction rates and strengths of lengths of rodent gut – was attached via a thin cord to a delicate lever which had a sharp point (stylus) at one end of it. This point was then placed against the smoked paper and then the motor was activated, causing the drum to rotate at a known speed. As the gut contracted, it moved the lever up and down which in turn caused the sharp point to displace carbon particles beneath the stylus point to leave a white tracing on the slowly moving blackened paper covering the metal cylinder. When the tracing had been made, it had to be removed from the drum without smudging it, and then immersed in some liquid, a smelly lacquer, that fixed the image to the paper. This procedure, I can assure you, is no less demanding on one’s manual skills than, say, preparing a tooth for an inlay or a bridge abutment or placing an implant.

Many generations of Robert’s dental students remember him fondly. Recently, someone with whom I studied dentistry at University College reminded me about his curious laboratory coats. He did not wear the long white coats that most scientists and many medics normally use. Instead, he wore a long coat coloured brown or ochre. Why he wore a lab coat that looked more like the work wear of an old fashioned grocer I have no idea – I never thought to ask him – but Robert did many things in his own inimitable style. Often his approach to things seemed eccentric at first sight, but usually after reflection you would realise that there was a lot of sense in what he did and how he did it.

Art and science



From my childhood until I qualified as a dentist in 1982, aged 30, I drew and painted a great deal. Creating pictures was one of my favourite pastimes. In the late 1970s when I was already studying to become a dentist, I joined a weekly print-making class. It was held in the West Hampstead studio of my mother’s cousin, the etcher/engraver Dolf Rieser (1898-1983; see: ). 

The image above is from an etching that I created in Dolf’s studio. It is a composition inspired by electron micography of intra-cellular structures. At the time I created it, I had just finished a PhD in a biological subject and was studying biology that was considered necessary to qualify as a dentist.  Interestingly, Dolf had also studied biology (genetics) in his youth, receiving a doctorate in the subject. He took to artistic pursuits after completing his studies in biology. Later in his life he wrote a book called “Art and Science” (published in 1972 by Studio Vista). Dolf was an inspiring teacher with a great understanding of compositional technique.

In 1982, I began practising as a dentist. It goes without saying that a dentist’s work involves a great deal of use of the hands and fingers. All day long, five days a week, I was doing the fiddly kind of things with my hands and fingers. Prior to qualification as a dentist, I had used my hands and fingers to create often complex images (drawings, paintings, etchings, and copper engravings). I found that my urge to create images diminished rapidly after I began practising dentistry. I suppose that the clinical activities satisfied my need to employ my manual dexterity in other ways. Sadly, now that I am retired I have not (yet) gone back to creating images. Now my fingers are kept busy at the keyboard, creating books and blog articles.

Learning by teaching


‘Doc’ mending a toaster in a friend’s home near Paris in 1978

Although my PhD supervisor was a full university professor of physiology, most people called him ‘Doc’. He was the pre-clinical tutor of the dental students, who undertook courses in academic rather than clinical departments of University College London (‘UCL’) during their first year of study. Doc’s PhD students were asked to volunteer to help teaching the basics of mammalian physiology to the dental students. I did this willingly. Once a week, I conducted tutorials for a group of six to eight dental students. Although I learnt a lot – teaching is the best was to learn, it was a case of the blind leading the blind. It was while doing this teaching that I met two of the people, who were to become owners of practices where I worked. They remembered me, but I did not remember them.

Once a week, the dental students carried out experiments in the physiology teaching lab. I assisted in the supervision of these classes. One of the experiments that the students undertook was pedalling on a bicycle rigged up to an electrical generator, which in turn was wired to a domestic lamp. The youngsters had to pedal furiously to get the lamp to glow, and while they did this their pulse rate and blood pressure was monitored.

Another experiment was connected with taste. The students had to prepare different dilutions of a chemical and used this to determine taste thresholds. The chemical used was phenylthiourea.  Some of the students could not taste this at any dilution. These people were lacking a certain dominant gene that allows people to taste this substance. The point of the experiment was to teach the students both about taste and, also, about genetic variation. Doc was keen for the future practitioners to learn that we are not all ‘built’ the same way.

Another experiment was examining the effects of various chemicals on the strength and frequency of contractions of short lengths of rodent gut in oxygenated tissue media. When we did this experiment and ones like it during our BSc physiology course, we attached the contracting gut too electronic force transducers which sent electric signals to an electronic graph drawing machine.


A kymograph attached to a pressure-measuring tube

Doc did not use this simple method when his dental students performed the experiment. The contractile tissue was tied to a long delicate metal lever which had a sharp point at the end of it furthest away from the fulcrum to which it was attached. Movements of the tissue caused the lever to move up and down. These movements were recorded on the smoked paper tightly attached to the cylinder (or drum) of an old-fashioned kymograph. As the lever moved in response to the contractions, the fine point at its end moved up and down and displaced the charcoal attached to the smoked paper producing a white tracing where the carbon had been removed.

Handling the kymograph drum was a tricky business. First the special plain white paper had to be tightly attached to the metal drum. Next, the drum was rotated above burning paraffin so that it became completely coated with the black particles in the smoke coming from the paraffin. When blackened, the drum and paper had to be removed from the smoking area and placed carefully on the spindle of the kymograph without touching the blackened paper so as to avoid removing the carbon coating. Attaching the gut to the kymograph lever was also tricky.

After the experiment, the paper covered with tracings had to be removed from the drum, again taking great care not to smudge the delicate layer of carbon and thereby obliterate parts of the tracings. Finally, the tracings had to be immersed briefly in a liquid lacquer that later evaporated and fixed the tracings (i.e made them immune to smudging). Only then could the students begin to make measurements of the amplitudes and frequencies of the contractions of the experimental material.

Doc had an ulterior motive in making his dental students use this highly obsolete measuring device. It was, he decided, an excellent way for future dentists to develop their manual dexterity.

As part of the pre-clinical course, Doc required that each of his students carry out a practical research project. He preferred simple projects such as measuring the blink rates of people sitting on Underground trains or assessing the rates at which peoples’ jaws moved whilst they were chewing gum. One group of students tested the theory (which has been proven) that people’s height was shorter at the end of the day than at the beginning. The main thing that concerned Doc was that his students were learning how to observe scientifically and systematically. It is most important, he felt strongly, for a clinician to be observant. He hoped that these projects would help to make these future dentists into skilled observers and therefore better clinicians.

Another reason for this project was for the students’ more immediate benefit. In the end of year physiology examination paper that he set for the dental students, he always inserted a question, which asked the student to write an essay about any aspect of physiology that interested him or her. Thus, simply by writing about the project undertaken, the student was guaranteed up to 25% of the marks.

Doc and his wife were perfect guides and became great friends during the time I was working on my PhD. I saw them socially often  for many years afterwards until their deaths. It was meeting and getting to know the dental student whom I attempted to teach that was one of the reasons that I strayed into dentistry.