26
X-rays: Bertha’s Hand
It’s unearthly, it’s truly mystical.
—Wilhelm Röentgen, 1895
Würtzburg, 1895
November the 8th of 1895 was a bleak, chilly day in the Bavarian town of Würzburg, home of the University of Würzburg, where Wilhelm Conrad Röentgen served as the rector and professor of physics. As rector, Röentgen was burdened with many academic and administrative affairs, but he still found time to give a few lectures and to conduct some research. Röentgen’s typical day began with a group session with students in the morning, a customary, heavy noonday meal at home with Frau Röentgen and their niece, who lived with them, followed by a short nap and a return to his office to take care of university business, returning for supper.
As the sun was setting in the late afternoon, Röentgen hurried home to prepare for starting a new avenue of research. This fifty-year-old professor had done distinguished work on the physics of solids and liquids, but recently he had been intrigued by some of the experiments on the cathode ray tube that had been carried out by a colleague, Professor Phillip Lenard, at the University of Heidelberg. Lenard had been studying so-called cathode rays that were given off in a closed, nearly complete vacuum tube when negative charged electrical particles called electrons were discharged from the cathode that was mounted in the tube.
Under these conditions, the cathode rays in the tube glowed in vivid colors and patterns. Lenard had been able to create conditions in which the rays escaped an inch or so outside the glass tube and into room air. This fascinating finding piqued Röentgen’s curiosity. He wanted to reproduce Lenard’s results and to explore some of the details of the escaping rays by pursuing some original ideas that he had.
A Dramatic Experiment
For his experiments, Röentgen needed a completely darkened space, for which he chose the cellar of his well-kept house, where he had established a laboratory. The several small cellar windows had lightproof curtains, but to be absolutely sure of darkness, he decided that all of the experiments would have to take place after the sun had set, which at that time of the year was 4:30 p.m. He left instructions with the other members of the household that no one should open the cellar door, since any sudden light would destroy his dark-adapted vision.
Röentgen had obtained a vacuum tube of the type that Lenard had used. The air inside the tube had to be removed by the use of tedious, hand-operated device that Röentgen’s laboratory assistant operated over the two-day period prior to any of the experiments. He also needed a source of alternating current, since the power to the house was direct current.
Before starting his experiments, Röentgen conceived of the idea of making a photosensitive plate using a piece of cardboard on which he had embedded fine phosphorescent crystals that would glow when the escaping rays hit it. He also thought to bring along two decks of playing cards to measure the penetration of the rays by seeing how many cards would be needed to block the rays between the source of the rays and the plate.
Before turning on the high voltage, Röentgen wrapped the entire outer surface of the tube with thin black paper so that the dim glow of the escaping rays would be more easily seen when the brighter light coming from the displays of light inside the tube were blocked out by the black wrapping.
He was now ready for the experiment. After the laboratory assistant, Röentgen extinguished all the lights, plunging the cellar into pitch-black darkness. It took a few minutes for his eyes to become dark-adapted. Even so, he had to search to locate the high-voltage switch. Increasing the voltage, he saw the cathode rays begin to appear outside the tube. He reached around for the phosphorescent plate that he had made, finally locating it at the other end of the bench where he had left it before turning out the lights. But when he picked up the plate, it was not dark, as he had expected, but rather it was showing a flickering faint green light.
What had caused that? At first, he thought it might be coming from the electrical coil that was used to convert the current. But that wasn’t it. Could it be a reflection in a mirror that was hanging close by? But there was no source for any reflection. It must be coming from the tube. To check that, he turned the high-voltage switch off and the green light disappeared. But turning the switch back on, it reappeared.
It certainly wasn’t the escaping cathode rays, since they couldn’t travel the distance of a meter between the tube and the plate at the end of the bench. Their range was only a few centimeters from the tube. Furthermore, the cathode rays were yellow, while the color of the light on the plate was definitely green.
He picked up the plate with its weak streak of green light and held it vertically. As he approached the tube, the light became a round green cloud, and as he moved even closer, it became a smaller but a much brighter spot. This mysterious ray was emerging through the glass wall of the tube, through the black paper cover, and through several meters in the room air. He stepped back and turned the plate around so that its cardboard backing now faced the tube. The light glowed as brightly as before. He realized that this had been a foolish idea in the first place, since if the rays could penetrate glass, they could certainly penetrate a thin piece of cardboard. But that conclusion prompted the question of what material could block the rays. He tried a few playing cards with no effect, then a whole deck and then two decks. The rays easily penetrated all of the cards. Groping in the dark, he located and tried a thick block of wood, but that didn’t stop the rays. Neither did a thousand-page bound handbook that he pulled down from a bookshelf close by.
By this time, Röentgen realized that whatever he was seeing was something new. These were rays generated from the cathode tube, but they weren’t cathode rays. They traveled in a straight line, and they could penetrate glass, two decks of cards, a thick piece of wood, and a thousand-page book.
A servant knocked on the cellar door to let him know that supper was ready. It seemed like a good time for a break to consider his next step. He said very little at the meal, eating hurriedly and abruptly excusing himself. He roamed the house, gathering pieces of several kinds of metals as well as bottles containing different liquids and various chemicals. Descending the staircase, he turned the device on and began the testing. Of all the objects he tried, only some of the metallic objects blocked the rays, and the best was a piece of lead pipe that was several millimeters thick.
Turning on a light, Röentgen sat down with his notebook to record all that he had observed during the evening. These mysterious rays were not cathode rays nor were they ultraviolet rays, since it was well known that UV rays could be easily blocked with light materials. What should he name these “new rays”? Looking at the alphabet, the next letter following U and V, the letters for ultraviolet, was W, but he rejected it because its shape tended to resemble U and V. The next letter was X, and X fit the bill perfectly, since it was original and carried the connotation of an unknown.
Röentgen’s next days were filled with many experiments, all aimed at defining more precisely the properties of the X-rays. He tested a whole host of materials to see which would block the rays completely, which only partially, and which not at all. Lightweight substances such as water, rubber, and aluminum sheets were no obstacles; heavier substances like concrete partially blocked the rays, but gold, silver, and lead stopped the X-rays completely.
Was his particular cathode ray tube unique in producing these X-rays? He tested several others and each produced X-rays. Could a magnet or a prism deflect the rays? Neither worked. But the magnet experiments proved that the rays were not charged electrically, unlike the cathode rays that bore negative charges. He became so immersed in his experiments that he began to skip supper, preferring to work uninterrupted well into the night.
A Great Breakthrough
By this time, Röentgen had learned a good deal about X-rays, but he needed a practical way to demonstrate them without having to use a phosphorescent screen in utter darkness. He toyed with the idea of taking a photograph of the plate, but almost immediately he realized that the photographic plate itself might be sensitive to the impact of the X-rays.
Simply turning the beam aimed at such a plate and developing it yielded a picture of the image of the X-ray. It was a great tool for all future work. Since the photographic plates were covered with paper to block out the daylight, and since the X-rays easily penetrated the paper covering, the need to work in darkness was no longer necessary. He could precede working in broad daylight.
What would the X-ray pictures look like if the beam were focused on some ordinary object? For his first try, he used a weight used in a laboratory beam balance. The rays pictured the exact shape and size of the weight. Since Röentgen knew that the wooden box in which the weights were kept was nearly completely transparent to X-rays, he focused the beam on the weights inside the box. The result was a perfect picture of the weights themselves inside the slight shadow of the box. X-rays could enable one to photograph the contents of a closed container from the outside!
When he tested the piece of lead pipe, Röentgen had accidentally allowed his hand to drop in the path of the beam when he was positioning an object on the plate. When he developed the plate, he saw a shadow that had the exact shape of the pipe, but also the detail of the bone of two of his fingers. He was seeing his own skeleton!
Röentgen reasoned that an X-ray picture of a hand might be the most convincing way to illustrate his discovery to others. He couldn’t use his own hand, because he couldn’t pose his hand and operate the tube at the same time. Thus far, no one in or out of the household suspected that a great discovery had been made in the cellar. He decided to ask his wife, Bertha, to be the subject. He knew that she could keep his secret. Well aware of his intense activities in the cellar for many days, she agreed to cooperate. He led her down the cellar staircase, placed her hand on the photographic plate, and asked her to hold it still for six minutes. Then he asked her to wait while he developed the plate. It showed a beautifully detailed picture of each bone of Bertha’s hand, including the shadow of the gold wedding ring on her third finger. When Bertha saw the plate, she was terrified. The idea of seeing her own skeleton provoked her crying out, “I have seen my death.” She stormed up the steps, retreated to her bed, and covered her head with a blanket.
After working for six weeks, Röentgen realized that he must quickly publish his results in order to establish scientific priority for his discovery. He sent brief letter entitled “Ueber eine neue Art von Strahlen” (On a New Kind of Rays) to the Würzburg Physical-Medical Society with a plea that it be published as soon as possible in the society’s proceedings. The editor agreed, and the published paper appeared on December 28, 1895.
Röentgen was aware that the society’s published proceedings had a small audience and would not reach the much larger array of scientists who were working in the same or related fields of research. He therefore purchased a number of copies of his published paper and mailed them along with a letter to a large number of well-known physicists in Berlin, Vienna, Paris, and London. Each letter also included X-ray photographs of the box of weights and of Bertha’s hand.
The News Spreads
The idea that X-rays could see what had been hidden spread quickly and widely. Furthermore, anyone could make X-ray pictures because the apparatus was easy to operate, was affordable, and gave quick results. In those early days, X-ray pictures could be taken in “portrait” studios, in coin-operated machines, and at meetings of newly formed X-ray clubs. The following ditty became an instant hit:
The Röentgen Rays,
The Röentgen Rays
What is this craze?
The town’s ablaze
With the new phase
Of X-ray’s ways.
I’m full of daze,
Shock and amaze;
For nowadays
I hear they’ll gaze
Thro’ cloak and gown
—And even stays,
Those naughty, naughty
Röentgen Rays.
Röentgen suddenly became famous throughout the world. He refused to patent his discovery, believing that it should be used freely for the benefit of mankind. By 1901, Röentgen’s discovery was universally lauded by the scientific world. He received many honors and awards as well as a long list of prizes, medals, honorary degrees, and memberships of learned societies. In several cities, streets were named after him. In spite of all this, Röentgen retained his modesty and reticence. In 1901, he was awarded the Nobel Prize in Physics “in recognition of the extraordinary services he has rendered by the discovery of the remarkable rays subsequently named after him.” He accepted the award but gave no lecture, and he announced that the monetary award would be contributed to the University of Würzburg.
As the use of X-rays spread throughout the population, no attention was given to any danger. After all, the rays were invisible, and people who were being X-rayed suffered no immediate ill effects. No one conceived of the idea that X-rays would be harmful in large amounts over time. There were a few hints that too much X-ray could be harmful. For example, a man who had submitted to an X-ray of his head two weeks previously found that all of his hair had fallen out.
Criticisms and Attacks
Following his discovery of X-rays in 1895, Röentgen published three classic papers containing the details of his experiments. These were the last of his publications. Despite the widespread news of this discovery, Röentgen’s personality did not permit him to celebrate his newly found fame. Indeed, he avoided any semblance of being a celebrated famous person. At the time, he was fifty years old and comfortably situated at the university. He had long been recognized as an eminent scholar of physics, and the year before, he was chosen as rector of the university, a great academic honor. His discovery of X-rays was widely hailed as “groundbreaking.”
Yet voices of critics of his work were soon being heard. Otto Glasser, author of a magnificent biography of Röentgen, quotes a letter written by Röentgen to his friend Zander as follows: “My work has received recognition from many quarters. … This is worth a great deal to me, and I let those who are envious to chatter in peace; I am not concerned about that.” But he was concerned, and every critical barb was a wound to his psyche.
Looking back, some critics questioned the originality and priority of Röentgen’s discovery by citing earlier events that were probably due to X-rays, but were not further investigated. Sir William Crookes had observed that unopened wooden boxes of photographic plates that had been placed under his cathode ray tube showed shadows that were attributed to light leaks. Others had had similar experiences with X-ray plates, but had only concluded that it was advisable to store the plates some distance from the tubes.
Many early cathode-ray workers, such as Lenard, stated that they had observed a great number of new phenomena, but none were ever followed up. A Philadelphia physicist had accidentally made an X-ray picture over five years before Röentgen’s discovery, but was unable to explain the phenomenon until Röentgen’s observations were reported. Although most scientists gave Röentgen full credit and the honors that were his due, the rumor mill persisted with such items that the discovery was an accident or that the first crucial observation of the fluorescence of the screen was made by an assistant. Seasoned scientists of the day acknowledged the role of chance in Röentgen’s work, but they also pointed out that only Röentgen had the gift of pursuing his discovery to unravel its basic cause.
Röentgen made no public responses to these charges, and over the period from 1895 to his death, he became an increasingly bitter man. One important effect of his bitterness was his refusal to publish anything further on X-rays after his three original communications. He also changed his will by stipulating that all correspondence, including some unopened papers about the discovery between 1895 and 1900, be burned after his death, a decision that regrettably was carried out.
Even though the news of discovery of X-rays was quickly widespread and often sensational, Röentgen assiduously avoided any self-publicity. He was very reticent by nature, and the many honors that he received were more of a burden than a pleasure. The University of Würzburg gave him the honorary degree of Doctor of Medicine, and he accepted honorary citizenship of his native town of Lennep. He declined all invitations to address scientific audiences on his discovery. Indeed, the only lecture he gave during his lifetime was the one he presented to the Würzburg Physical-Medical Society.
He declined the offer of nobility by the prince regent of Bavaria, who later bestowed the title “Excellency” on Röentgen. In 1901 he became the first Nobel laureate for physics and traveled to Stockholm to receive his award.
In 1900 Roentgen left Würzburg to take charge of the Physical Institute of the University of Munich, where he resumed his earlier work on the physical properties of crystals. After his retirement in 1920, he was given permission to use two rooms in the institute, where he continued to work until a few days before his death on February 10, 1923.
The Dangers of X-rays
An early alarm was sounded when Clarence Dally, Thomas Edison’s chief laboratory assistant, suffered numerous radiations “burns” on his hands and face during his work on X-rays. A short rest away from the laboratory did not prevent recurrence of the burns, which developed into severe ulcerations and the development of a malignancy that required amputations of both of his arms, and that eventually led to his painful death. The experience was enough for Edison to abandon all X-ray projects and to never submit himself to X-rays for the rest of his long life.
Studies of the effects of X-rays on living cells in research laboratories were demonstrating the harmful effects on living cells and organisms. As early as 1929, Hermann Muller was awarded the Nobel Prize for his groundbreaking work that showed that X-rays produced mutations in the chromosomes of the fruit fly. These scientific advances plus the increasing cases of radiation sickness led to the development of safety regulations designed to protect both patients and personnel from harmful effects of X-rays. Even so, as late as the 1950s, many shoe stores still operated X-ray machines, which later were incriminated as causing testicular cancer in boys.
Comment
When Röentgen spotted that green light on the phosphorescent plate, he had the good sense to drop his original study of cathode rays and concentrated on unraveling the nature of these new rays. Röentgen’s story is a wonderful example of an accidental discovery. In Röentgen’s case, as in all other cases of chance discovery, the discoverer observes a completely unexpected event and stops whatever he was doing to pursue a new line of work aimed at understanding the significance of what he has just observed. Röentgen immediately grasped the significance of his discovery. He readily abandoned his study of cathode rays and launched a new investigation of the seemingly mysterious X-rays.
Röentgen’s life is a sad tale of short-lived jubilation at his discovery, followed by a series of painful blows, however false, to his psyche, which resulted in a bitterness that persisted over the remaining twenty-eight years of his life. The world gave Röentgen its acclaim and acknowledged his discovery as one of the greatest in many decades, but in so doing, it made him a bitter man.
REFERENCES
Assmus, A. “Early History of X-Rays.” 1995. http://www.slac.stanford.edu/pubs/beamline/25/2/25-2-assmus.pdf
Friedman, M., and G. W. Friedland. Chap. 6 in Medicine’s 10 Greatest Discoveries. New Haven, CT: Yale University Press, 1998.
Glasser, O. “Strange Repercussions of Röentgen’s Discovery of the X-rays.” Radiology 45 (1945), 425–427.
Miller, A. “The History of the X-ray.” Homepage.