Wilhelm Conrad Roentgen

Joseph C. Bell
Prof. Of Radiology
University of Louisville School of Medicine 1929
Typed for the Innominate Society

          In selecting the life of Roentgen for the subject of my paper tonight, I have chosen one whose work has been so recent that it scarcely belongs to the realm of history. However, his discovery of the ray that bears his name has influenced medicine to such a degree that Roentgen’s life should be of interest to us. In medicine, as in all other lines of human endeavor, we are prone to accept an established fact, or a discovery, with little thought of its origin.

          Wilhelm Conrad Roentgen was born in Lennepp, in the mountainous region of the lower Rhine, March 27, 1845. His father was a simple, reserved, industrious farmer of German extraction. These characteristics were, in a measure, transmitted to his son. The mother was of Dutch descent and to her influence may be attributed Roentgen’s imagination, modesty, simplicity and love of truth.

          Roentgen’s early childhood was a happy one and was spent in Holland. He was an only child and during his youth he showed no characteristics different from other children of his age. In school he was an indifferent student and cared more for wondering in the fields and woods, than for his books. However, he was a wide-awake boy and was interested in athletics.

          After finishing primary school he was sent to an agricultural school in Apeldoorm, Holland to learn to be a farmer. There were other plans for him, however, for shortly after entering this school, he was accused by the authorities of a part in some simple prank. Roentgen readily admitted his guilt, but refused to disclose the names of those associated with him. He firmly maintained his position and as a result, was expelled. This was a great blow both to him and to his parents, but the latter understood his attitude and supported him in it. He then took an examination that would have admitted him to the secondary schools, but filed to pas. These happenings proved to be a turning point in Roentgen’s life. Later developments made it seem likely that they were “Blessings in disguise,” for they removed him from the lockstep of education then in vogue and gave him freedom of thought and action. Then followed a period spent at home in independent reading, study and contemplation.

After the period at home Roentgen entered the Polytechnical School at Zurich. He selected this school because no entrance examinations were required. Here, at first, we find him only an average student, but later he came under the influence of a great teacher ad scientist, Clausius. Roentgen became deeply interested in the work of this teacher and saw in it a new opportunity to delve more deeply into the secrets of nature. He was delighted with the precision and industry required in his investigations.

From this time on Roentgen’s progress was rapid and he became an outstanding student. Upon graduation he was chosen as an assistant to Kundt. The latter aided him greatly in developing exactness, thoroughness and skill in experimentation.

Kundt took him to Wurzburg with him but Roentgen was refused a place on the teaching staff at the university there because of the irregularity of his early training. Fortunately, for him, Kundt was called to Strassburgh and Roentgen accompanied him. There Roentgen did excellent work and his advancement was rapid. At the age of thirty he was made professor of mathematics and physics at Hoenheim. One year later he returned to Kundt, at Strassburgh, as associate professor of theoretical physics, and after three years, at the age of thirty-four, he was made full professor of physics at Giessen. Here he stayed for ten years, happy in his work of teaching and in his investigations. He was an inspiring teacher and was able to impart to his students his exact and independent methods of investigation.

In the year, 1888, when forty-four years of age, he was called to Wurzburg, where he continued his teaching and experimenting. It was here that his epoch making discovery of the roentgenrary took place.

As we have followed Roentgen’s life, it has been noted that from the time of his awakening in the Polytechnical School in Zurich, up to the period at Wurzburg, his progress was rapidly and progressive upward. During this time period he had done much careful experimentation and had published many papers. He became recognized as one of the outstanding physicists of his time.

Much of his investigation had concerned itself with the changes in physical, chemical and electrical properties of matter, with variations in pressure. We can picture him at work on this problem in his laboratory in the spring of 1895. We see a tall, serious, thoughtful man with kindly, intelligent eyes standing before a glowing Grookes’ tube. He was investigating the changes in fluorescence with variations of pressure in the tube. This had been done before and Leonard had brought the cathode rays out of the tube through a thin aluminum window and had made an exhaustive study of them. Their various properties had been determined and it had been noted that photographic plates became fogged with in the vicinity of the tube.

This particular morning Roentgen had prepared for an expedition into the woods and had brought some photographic plates into the laboratory with him. Being called from the room, he said the energized tube on a book containing a key for a marker. The book happened to by lying on one of the photographic plates. When he came back he developed this plate, together with others, that had been used during his outing, and to his surprise, the image of the key used as a bookmarker, appeared on it. Theses happenings were purely accidental but then the trained mind of a scientist came into play. He repeated the happenings of the morning, step by step, and again the image of the key appeared. Roentgen now recognized that something very unusual had been observed and he suspended all other work and began a searching investigation of this phenomenon.

          He found if the energized tube was surrounded with black paper, a piece of cardboard coated with platino-barium cyanide fluoresced when in its vicinity, and that images of various things were shown on this screen when placed between it and the glowing tube. He found that the bones of human hands could be demonstrated on the screen in this way, and that they could also be shown on a photographic plate after exposure to the rays from the tube. He recognized that some agent had penetrated the paper surrounding the tube and that this agent was capable of making the screen fluoresce, and discovered that certain other substances had this property of fluorescence when near the tube. It was observed that the photographic plate was sensitive to this agent and he used the plate to check the observations made with the fluoroscopic screens. This agent was determined to be a ray, for it traveled in straight lines form the source of emanation. For convenience he termed in an x-ray because of its heretofore-unknown properties.

All substances were found to be transparent to this ray but in greatly varying degree. Paper, wood and many other substances were seen to be highly so, while lead, gold, platinum and others, were found to be transparent only in a very limited degree. Roentgen observed that the penetration of the ray varied inversely with the thickness of the substance to be traversed by it, and he saw that the penetrability depended partly, but not entirely, upon the density of the substance. It was discovered that photographic places could be protected form light by wood, or cardboard containers, but that thus encolosed they were sensitive to the x-ray. He observed that the retina of the eye was not sensitive to the ray and that the ray could not be reflected, or so far as he could tell could not be refracted. He found that the rays could not be concentrated with lenses and that they could not be detected by a magnetic field.

The intensity of the x-ray was seen to vary inversely with the square of the distance form its source and absorption in the air was observed to be much less at a given distance than was the case with the cathode ray. The source of the x-ray was discovered to be the point where the cathode rays struck the wall of the tube and this source was observed to change when the cathode rays were bent by a magnet. He discovered that x-rays were generated when the cathode rays struck any substance, but he found that platinum was best suited as a source in his work. Roentgen constructed a tube with a cup shaped cathode so placed that it would concentrate the cathode rays on the platinum target wet at an angle of forty-five degree to the cathode stream. He recognized that this ray was entirely different from the cathode ray, ordinary light or ultraviolet light. He was not able to determine the exact nature of the ray; but suspected that it bore some relationship to light.

These were some of Roentgen’s principle findings, and in a modest paper entitled “ Concerning a new kind of ray,” he presented them to the Physio Medical Society of Wurzburg in December 1895. Two other papers followed the next year reporting other investigations into the property of the ray. His initial presentation was greeted with prolonged applause and almost immediately the findings were reported throughout the world. The discovery and the discoverer were exclaimed everywhere. These observations were substantiated, and in a very short time many physicians were making their own x-ray plates as a part of their medical diagnosis.

At the end of the meeting when Roentgen’s second paper was read, an x-ray place was made of the hand of the chairman of the meeting, Herr Von Kolliker. Von Kolliker proposed that this ray should be called the Roentgenray instead of the x-ray as was suggested by the discoverer. This name was adopted by the society and is accepted one at present.

 As is usually the case with great discoveries, there were those who strove to detract form the honor to Roentgen. Some said that the finding was purely accident and others said that the discovery had really been made by one of Roentgen’s technicians. To these Roentgen refused to reply.

Roentgen fully appreciated the far-reaching affects of his work, but after reporting subsequent investigations in two papers he left the development of the Roentgenary to physicians and to others and returned to his chosen field of teaching and laboratory experimentation.

He refused to accept any material advantage from his discovery. However, honors were showered upon him. He was given the Rumford medal of the Royal Society of London in 1896.  In 1900 he received the Bernard Medal of Columbia University and the Nobel Prize. He was made a member of the Prussian and Bavarian Academies of Science and was elevated to the nobility. Throughout all he remained the same modest, industrious, kindly and retiring person that he had been from early in his career.

Roentgen remained in Wurzburg until 1900 when he was called to the University of Munich as director of technical physics. He held this chair until retirement in 1919. His last years were spent in a suburb on Munich. This period was an unhappy one for him, for many of his old friends had died and he was never so happy a when at work. After a very short illness he died February 10, 1923 of cancer of the rectum.

While Roentgen’s discovery of the x-ray was to us his most important work, his other investigations and discoveries alone entitle him to a place as one of the greatest physicists of all times. He produced fifty-five important publications and his researches covered such subjects as specific heat of gasses, a study of isothermal crystals, of calorimetry, dust figures, the size of molecules, the compressibility of water, absorption of heat by vapor, the influence of pressure on various substances, pyroelectricity, the electro magnetic effect of polarized light in gasses and the electrodynamic power produced by the motion of a dielectric in a homogeneous electric field. The latter investigation is said to be of more importance in theoretical physics than is his discovery of the x-ray.

The astounding thing is the scope of completeness of his investigation of the properties of his discovery. In three short communications produced within a little more than a year’s time, he established practically all of the basic properties of the roentgenray known at present time. Not only did he do this, but also he foresaw the far-reaching effects of his finding on other branches of science. It is impossible to give any evaluation of the ultimate result of his work for only a few of the possibilities of the roentgenray are known as yet. It is now extensively used in both medical diagnosis and treatment, and it is beginning to play an important part in modern industries. It is opening entirely new fields of investigation in the natural sciences.

With the death of Roentgen, the world lost a great scientist, and medicine and humanity in general lost a great benefactor.