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.