Object of the Month: The Unknown X

3 January 2012

 Double focus X-ray tube. Science Museum / Wellcome Images.
[object Object]

Double focus X-ray tube. Science Museum / Wellcome Images.

When Wilhelm Röntgen made the first x-ray image of his wife’s hand, the world was astounded. William Birnie looks at a seemingly magical tool of medical vision whose dangers were not immediately apparent.

With the discovery of the x-ray, physicians were allowed their first non-invasive look inside the human body and, unsurprisingly, X-rays quickly proved to be extremely useful, as both a diagnostic and therapeutic tool.

In November 1895 the first X-ray was taken by Wilhelm Röntgen (1845-1923), in Würzburg, Germany, and it was of his wife’s hand. He called them X-rays ‘for the sake of brevity’. The discovery was a culmination of more than a century’s research on electrical discharges in evacuated vessels. There’s no doubt X-rays had been generated many times before their discovery as, in the 1880s, experiments with the cathode ray tubes of Sir William Crookes were very popular. Moreover, Crookes himself had been baffled as to why the photographic plates he stored near his cathode ray tubes kept repeatedly fogging up.

Röntgen used such tubes, covered in black paper, to study the fluorescence produced when cathode rays struck the glass wall of the tube. During one such experiment he noticed that when the discharge was passed through the tube, some crystals of barium platinocyanide spread on a piece of card nearby glowed luminously. In tracing the origin of the light back to the tube a great discovery was made.

Medical X-rays are produced by letting a stream of fast electrons come to a sudden stop at a metal plate. This double focus X-ray tube works by using an alternation current which accelerates electrons towards an aluminium plate, thus producing an X-ray at both ends of the tube. The rays are capable of penetrating some thickness of matter and the X-ray image is created due to different tissue absorption rates: calcium in bones absorbs X-rays most, therefore the bones look white, whereas fat and other tissues absorb less and look grey. Lungs look black on an X-ray image, as air absorbs the least.

Early test objects included the hands of physicians and technicians (with serious consequences later), and model skeleton hands with forearms, made from a frame with silver paper added to simulate the tissues and bones. Small animals such as frogs and snakes were also used.

Scientists all over the world today are closely involved with X-rays. This connection dates back to shortly after Röntgen’s discovery, which was exploited rapidly even 100 years ago. By May 1896 the first X-ray journal, Archives of Clinical Skiagraphy, was published in Great Britain (skiagram was the term used in 1896 for what we would now call a radiogram). In the same month the technique was first used on the battlefield during the Italian-Ethiopian campaign, with physicians able to locate bullets inside wounded soldiers.

The public’s imagination was understandably captured by the suggestion and potential of X-rays. It was incredible that these rays could photograph inside the body and find bullets in soldiers. Public reaction in 1896 was widespread and immediate with the headlines mostly positive: ‘Electrical Photography Through Solid Body’ (Electrical Engineer, New York) and ‘Searchlight of Photography’ (The Lancet). Not all headlines were quite so favourable concerning the new technology, with the London Pall Mall Gazette stating, ‘we are sick of the Röntgen rays… you can see other people’s bones with the naked eye, and also see through eight inches of solid wood. On the revolting indecency of this there is no need to dwell.’

The use of X-rays was one soaked up readily by those members of the public who attended new X-ray lectures. A small fee would be charged to those audience members who wished, and volunteered, to have their hands and purses X-rayed.

Radiography is the first and foremost use of X-rays. It is an extremely familiar one with a variety of applications. For instance, in addition to being used in medicine, the X-ray has been used to detect structural flaws in materials, by chocolate manufacturers to ensure the absence of any metallic particles, to detect pearls in oysters, for security checks on luggage, and to examine Egyptian mummies, plant specimens, and old oil paintings. More familiarly, in the 1920s a veterinary school had a piece of specially designed apparatus installed in order to aid their investigations of bone diseases in army horses.

The dangers of using X-rays were not fully understood initially, with the hands of physicians and technicians used as early test objects leading to dreadful results, from dermatitis to skin cancer from radiation ulcers. Yet there were early indications. In 1896, the Röntgen Society of London formed a committee on X-ray injuries, with a similar initiative following in America several years later. The biological effects were also noted by Thomas Edison and Dr. W. J. Morton, who both suffered from sore eyes after working with X-ray tubes for a number of hours. Although lead protective clothing was worn by some in 1910, it was not until 1921 that a national committee in Britain endorsed protection recommendations.

There was also another reason why safety was seen as being of utmost importance. The use of X-rays was no longer only in the hands of doctors and experts. The commercial applications were extremely wide and it made its appearance in factories and shops. An example of war-time application included the examination of foreign ammunition of unknown construction. This had been hazardous to say the least before the development of metal radiographs.

If Röntgen’s semi-accidental discovery had not taken place, modern medicine would have been deprived in an unimaginable way. A book entitled X-Rays, Past and Present, which was published in 1927 and aimed to give the general reader a history of X-rays, makes an interesting point in its closing pages by stating: ‘not the least important result of the development of X-rays has been that they have formed a common link between other branches of science that hitherto had drifted into something approaching independent existences.’ X-rays, with the subsequent examination into their effect on physiological tissue, allowed the concept of our bodies being nothing but special differentiations of electrical charges to become much more tangible and appreciated than it had ever been before.

William Birnie is a Visitor Services Assistant at Wellcome Collection. You can contact him at w.birnie@wellcome.ac.uk.