Collecting and Recollecting: Gifts from the Recent Past

X Ray

Late in the nineteenth century, a group of scientists was conducting experiments in which they discharged electric currents through air in a partially evacuated (Crookes) tube, inside of which stood a negative and positive electrode. The observers could watch the behavior of the stream of particles produced, called cathode rays (later identified as electrons). To overcome the limitations placed on studying cathode rays, which were thought unable to penetrate the glass of the Crookes tube, the German physicist Philipp Lenard designed a tube with a very thin aluminum window through which . . . the rays could pass, and flow a few centimeters into the outer air before being dissipated. Their exit was often detected by fluorescence of a paper saturated with a barium compound.

21. William Conrad Roentgen The German physicist won a Nobel Prize for his discovery of the X ray in 1895. Courtesy of the American College of Radiology

Wilhelm Roentgen, a professor of physics and director of the physics institute at the University of Wurzburg in Bavaria, became interested in cathode rays in the spring of 1894. At some point during this time, Roentgen had an idea. Perhaps cathode rays did penetrate the glass of ordinary Crookes tubes, but had been undetected by previous experimenters because the luminescence the rays could produce on a fluorescent screen was obscured by light generated within the tube itself. Roentgen tested his idea on November 8, 1895. He covered an ordinary Crookes tube with black cardboard, darkened the room, and, before setting up the fluorescent screen, discharged the tube to make sure its light did not pass beyond the covering. To his surprise the screen, lying on a bench about a yard from the tube, emitted a faint glow. Astonished, he again discharged the tube -- the phenomenon appeared once more. He repeated the experiment with the screen at ever greater distances -- with the same result. Since he knew cathode rays had never been reported to travel more than several centimeters through air, he thought it likely that some other kind of radiation was at work.

In succeeding weeks he conducted more experiments, which confirmed that these emanations were not cathode rays. The experiments that Roentgen wrote about disclosed that the new radiation could penetrate solid objects -- in general the lower the density the better. Thus they easily passed through a 1,000-page book, a double pack of cards, wood, and hard rubber. They did not easily pass through more dense substances, such as lead or bone: "If the hand be held before the fluorescent screen," wrote Roentgen, "the shadow shows the bones darkly with only faint outlines of the surrounding tissues." He found that these phenomena could be captured on photographic plates as well as on fluorescent screens, and demonstrated this by producing, along with pictures of inanimate objects, a bony portrait of his wife's hand . . .

22. X-ray display with photographic plate

Interest immediately focused on the fact that the X-rays, as Roentgen named them because he did not know their composition, could reveal the skeleton within its case of flesh. The picture of Frau Roentgen's hand, taken to illustrate the rays' powers, was soon displayed in newspapers and scientific publications all over Europe and the United States. "The realism of this weird picture" reported Popular Science Monthly,"simply fascinated all who beheld it." "Hidden Solids Revealed," proclaimed the New York Times;"A Photographic Discovery Which Seems Almost Uncanny," announced the St. Louis Post-Dispatch.

23. X-ray of Bertha Roentgen's Hand Roentgen soon found that photographic plates were sensitive to the newly discovred rays. He convinced his wife to participate in an experiment. Roentgen placed her hand on a cassette loaded with a photographic plate. He then aimed the activated cathode ray tube at her hand for fifteen minutes.* When the image was developed, the bones of her hand and the two rings she wore were clearly visible. Horrified at the result, Bertha Roentgen, like many to follow, saw in the image a premonition of death. *An x ray of the hand requires an exposure of about 1/25 to 1/50 of a second today.

Coolidge X-Ray Tube
Manufactured by Picker International, Incorporated
circa 1920

X ray tubes used in radiology today are based on the design of this tube by William Coolidge, a physicist at the General Electric Research Laboratory in the early 1900's. The earliest X ray sources were partially evacuated glass tubes which would not work unless a residue of gas remained inside. These tubes were balky and unpredictable because the properties of the residual gases changed when they were heated, and varied from day to day as well as from minute to minute.

Coolidge's tube was a vacuum that used an electric filament to generate the electrons which would produce the X rays. He applied for a patent and introduced his tube to the medical world in 1913. After preliminary tests, Dr. Coolidge turned the tube over to a practising radiologist, Dr. Lewis Gregory Cole, for clinical trials on patients.

24. X-ray Tube Factory
c. 1900
Courtesy of the American College of Radiology

The eminent New York City physician enthusiastically endorsed Coolidge's tube, describing it as more accurate, stable, consistent and capable of producing sharper images than the old gas tubes. The Coolidge tube quickly became a standard component of x-ray equipment. Ruth and Edward Brecher, authors of The Rays, A History of Radiology in the United States and Canada,write:

Radiologists equipped with the new tube could do new things. They could do the old things better. They could more readily teach their techniques to their colleagues and their successors. As one result of the simplicity and the vastly greater dependability of the new tube, many additional physicians were attracted to radiology. Thus, radiology was able to evolve as one of the major specialties in the practice of medicine.

Gift of Lee McCauley, MD, Wichita Falls, Texas

United States Army X-Ray Manual
New York: Paul B. Hoeber
1918

Immediately after the United States entered World War I, many of the nation's leading radiologists joined the Roentgenological Division of the Army Medical Corps. Army training schools for additional radiologists were established in New York City, Boston, Philadelphia, Pittsburgh, Baltimore, Richmond, Chicago, Kansas City and Los Angeles. An Army X-Ray Manualwas issued and became the guidebook for countless newly trained radiologists. The radiologists who had joined the Army and those newly trained by the Army went on duty in all theaters of action and at bases throughout the United States. Many received their first experience with the new Coolidge tubes and other improved apparatus during their Army service. Their accomplishments on active duty awakened other physicians in the medical corps to the many uses of the X ray.

At the end of the war, many physicians newly trained in radiology by the Army returned to civilian practice, many left the service resolved to take radiological training, and almost every demobilized physician returned home with a heightened respect for radiology.

Gift of George J. Garwood, RN, Vinton, Iowa

Principles and Practice of X-Ray Technic for Diagnosis
By John A. Metzger, MD
St. Louis: C.V. Mosby
1922

This manual was prepared by a professor at the School for Graduates, Medical Department, University of California, Southern Division, Los Angeles. Containing 61 illustrations, this guide includes a description of equipment and appliances necessary in an X ray laboratory, and a table of exposures that have worked well for the author. Each photograph demonstrates the position of patient and equipment to achieve the best X ray image.

Although risk of radiation to operator and patient was known at this time, its extent was not yet understood. Radiologists had become familiar with the delayed effects of excessive exposure, but the very late effects -- arising more than two decades after the exposure -- had not yet had time to make their appearance.

Gift of George J. Garwood, RN, Vinton, Iowa

The dangers of secondary radiation exposure have been addressed; this photograph shows the x-ray operator wearing a protective apron and the tube enclosed in a lead glass shield.

Recreation of the First Demonstration of X rays
In January 1896 Roentgen publicly demonstrated the action of the rays. Roentgen imaged the hand of the famous anatomist Albert Rudolf von Kolliker, who then proposed to call the new rays Roentgen rays.

Printed in the series: A History of Medicine in Pictures, presented by Parke, Davis & Company. Painted by Robert A. Thomas

25. Roentgen: Invisible Rays that Save Lives
Scientist filled the room at the University of Wurzburg, Germany, in 1896, when Wilhelm Conrad Roentgen (1845-1923) demonstrated his newly discovered x-rays by photographing bones in a hand. Within a year, x-rays were being used world-wide for medical and diagnostic purposes.
One of a series: A History of Medicine In Pictures, presented by Parke, Davis & Company.
Directed by George A. Bender
Painted by Robert A. Thomas