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Pan-American Exposition of 1901

X-rays at the Exposition

The first medical use of Wilhelm Roentgen's "x-ray light" occurred in 1896, one year after his discovery. Although x-ray apparatus were on display at the Exposition, no one thought to use it on the wounded President McKinley to locate that second elusive bullet.

In her 1997 book Naked to the Bone, Bettyann Holtzmann Kevles1 describes the following account McKinley's treatment with regard to the X-ray machines available at the Exposition.

…Altogether separate from the hospital was a Science Hall which had an X-ray machine with it's own dry-cell battery on display…. No one suggested using the X-ray machine in the Hall of Science.

…After surgery, McKinley was taken to a private home where, for a few days, he seemed to be improving. Thomas Edison dispatched Clarence Dally, his number one X-ray assistant, to accompany his best new X-ray machine from New Jersey to Buffalo. As the train sped north, an independent group in Buffalo set up a sort-of presidential look-alike contest in preparation for Dally's arrival. Fat men lined up in the hope of being selected as the stand-in to test the X-ray for the president. When the X-ray team arrived, Dr. Vertner Kenerson, who boasted the same fifty-six inch waistline as the president, had been selected. Kenerson went to the house where McKinley was supposedly recuperating and, in a room across the hall from the president, lay on his side with a light in front of him and a fluoroscope behind for the twenty minutes it took to get a picture showing "the entire interior arrangement."

…McKinley himself had asked to have an X-ray taken as reassurance that the bullet hadn't settled in any vital spot. But his doctors declined, not wanting to subject him to whatever movement he would have to make to get to the machine. …Eight days after the attack, he was dead from gangrene."

Basic Components of the 1901 X-ray Machine

The chief parts of an X-ray outfit are a static machine, or an induction coil; the vacuum tube with its supporting apparatus; the fluorescent screen or fluoroscope; and the photographic plate.

Thumbnail image - Portable x-ray machine

Portable X-ray Machine. Cut of portable apparatus for use on 110-volt circuit. The smaller box contains the coil; the larger, the interrupted electrolytic interrupter, two vacuum tubes, and the tube-holder. The tube-holder is shown fastened to the smaller box.

The X-rays are produced in the vacuum tube, and this tube may be excited by

  1. Static Machine; the two types of which are
    1. Influence Machine.
      Forms of: Holtz, Toepler-Holtz, Voss, Wimshurst.
    2. Plante Rheostatic.
      Form of: Thomson Dynamo Static.
  2. Induction coil; the two types of which are
    1. Ordinary Page, or Ruhmkorff, coil.
    2. Tesla, or high frequency coil. Form of: Thomson coil.
Thumbnail image - static machine

Static Machine. Large static machine with four revolving plates 183 cm (6 feet) in diameter, and four fixed plates (6 feet, 4 inches) in diameter. The front of the case has been removed.

  1. Static Machine. -The static machine may be driven by hand, or by any form of motor such as an electric or water motor, or a gas engine; and may be self-exciting or be excited by a small Toepler-Holtz or Wimshurst machine.
  2. Induction Coil. - The electric current for the induction coil may be obtained from
    1. Primary battery (low voltage).
    2. Storage battery (low voltage):
      1. Charged by gravity cells;
      2. Charged from street main.
    3. A dynamo which generates a continuous or alternating current of either high or low voltage.
    4. The street main (high voltage); current continuous or alternating.

Ironically, in 1901, the year William McKinley was assassinated, Wilhelm Roentgen was awarded the Nobel Prize for his discovery.


1. Bettyann Holtzmann Kevles, Naked to the Bone : Medical Imaging in the Twentieth Century. New Brunswick, N.J. : Rutgers University Press, 1997.