Naked
to the Bone
Medical Imaging in the Twentieth Century
By BETTYANN HOLTZMANN KEVLES
Rutgers University Press
CHAPTER
ONE
The
Discovery of X-Rays
Seeing Is Believing
On a hot, humid July morning in 1881, President
James A. Garfield arrived early at the old Baltimore and Potomac
depot on the corner of Sixth and B Streets in Washington, D.C. He
had left his wife, Lucretia, with two of their four children the
day before at what we would now call the "summer White House"
in Long Branch, New Jersey, and returned to Washington before he
was to head north again to Williams College in Massachusetts, where
hundreds of students and parents anticipated seeing the president,
a distinguished alumnus, receive an honorary degree. The waiting
room at the station was almost empty when he arrived and, concerned
about the time, Garfield checked with a policeman. Not to worry,
Officer Kearney assured him, he had ten minutes before the 9:30
train was due. We know this because the policeman later testified
in court that he had moved on, then turned abruptly at what sounded
like a firecracker in time to see a bearded man fire a second time
before anyone could interfere. This would be the last presidential
shooting before the discovery of X-rays.
In
a matter of seconds the district health officer, Dr. Smith Townsend,
who happened to be nearby, was at Garfield's side, cutting through
the president's gray traveling suit to probe the bullet hole with
his bare index finger. Dr. Townsend estimated that the bullet, which
had entered from behind, had turned right at the kidney and lodged
somewhere in the small of his back. They would not know for sure
until the inevitable autopsy. The president was calm enough in the
chaos that followed to ask to be taken back to the White House.
Someone yanked mattresses from a nearby Pullman car and piled them
into an express cart for a makeshift ambulance. By the time the
president had been carried back up Pennsylvania Avenue, the south
bedroom of the White House had been turned into a hospital. Despite
Townsend's prediction, Garfield, a vigorous man of forty-nine, rallied.
Soon he was sitting up and sipping fluids.
Half
a dozen doctors collected in the White House, all stymied because
they couldn't find the bullet. They pondered the president's condition
and monitored his progress with state-of-the-art instruments--stethoscopes
and thermometers. They were obsessed with the bullet: without knowing
where it was, they couldn't decide whether to leave it alone or
try probing blindly. The hidden bullet dominated national news while
White House physicians argued publicly. Editorials all over the
country demanded "Where is the bullet?" In an age that
had seen the invention of the telephone and telegraph, the public
demanded that someone find a way to detect a bullet lodged inside
the president's body.
But
even sophisticated people who were getting used to letting doctors
look into their eyes with ophthalmoscopes or listen to their hearts
with stethoscopes had no reason to imagine that they would see the
bullet. When they said "locate," they meant some kind
of metal detector.
Listening
for the Bullet
A week after the crime, Simon Newcomb, the physicist-astronomer
who headed the Naval Observatory in Washington, mused at a news
conference that it might be possible to locate the bullet by the
process of electrical induction. But he immediately dismissed the
idea as too complicated to make workable in time. Alexander Graham
Bell, the Scottish inventor who had won international fame with
his telephone, disagreed. Convinced that a machine that combined
induction with some aspects of his telephone could save Garfield,
he wired Newcomb to say that he thought he could rig up such a machine
quickly. The next day, Bell left his home in Boston and, with his
assistant Sumner Tainter, took a train to the capital. Bell was
then at the peak of his popularity. In 1881 his Bell Telephone Company
had become the first corporation ever to gross a million dollars
in a single year. Bursting with confidence when he arrived in Washington,
Bell recalled for the press a remarkable "induction
machine" he had seen three years earlier in London, an
apparatus that could generate an electrical field around a man.
With such a machine, Bell asserted, an operator could pass an exploring
coil over someone, like a divining rod seeking hidden water: the
moment the coil passed over metal it would trip a mechanism to signal
its find. The machine would literally get a ringing response from
a lead bullet.Bell drove directly from the depot to the White House,
then a parklike oasis in the mosquito-ridden swampy city. (Over
the next three weeks, four staff members would come down with malaria.)
Washington was less developed than Boston or New York City, but
like most other American cities it had gas lighting and indoor plumbing
for the well-to-do, empty lots awaiting development, and very few
paved streets.
To protect the president from the oppressive heat, his staff moved
him to the north bedroom where Simon Newcomb, with the help of the
naval engineers, rigged up what may have been the first electrical
air-conditioning system. (It lowered the temperature twenty degrees
by forcing air over six tons of ice blocks in the White House basement.
The air was then dehumidified and conveyed through the hot-air registers.)
As the president lay sipping iced champagne, Bell and Tainter went
to work. Starting from scratch, they scavenged equipment from all
over town: huge induction coils that the physicist Joseph Henry
had left to the Smithsonian, twenty enormous Bunsen elements that
were used to ignite the gas lamps in the
Capitol, and an electric motor from the Western Union Telegraph
Company. The capital, like the rest of the nation, was decades away
from providing electric power to every wall of every building. With
this jerry-built arrangement, Bell and Tainter first experimented
on themselves by holding bullets in their mouths, clenched fists,
and armpits, taking turns passing a coil over their bodies and listening
for a faint telephonic click. Bell fine-tuned his machine by firing
bullets into slabs of freshly slaughtered beef and experimenting
with a bullet-ridden corpse whose build resembled the president's.
On July 26, twenty-five days after the shooting, Bell wheeled his
apparatus into Garfield's bedroom. Under the gaze of five doctors,
he moved the coil slowly over the dying man's body. For one instant
he seemed to hear a signal, but the source turned out to be unsuspected
metal coils inside the presidential hair mattress.
The idea was sensible, but the method was crude. It would be another
thirty years before anyone successfully used sound waves to locate
hidden objects (and then the objects would be icebergs after the
sinking of the Titanic in 1912), and another fifty years before
sound waves would be able to capture a picture of anything, including
a bullet, inside a body.
President Garfield succumbed on September 19, eighty days after
the attack. On the following day, an autopsy showed that the bullet
had in fact turned left, 180 degrees away from Dr. Townsend's estimated
path, and was lodged to the left of the vertibrate near the pancreas.
The reputations of Townsend and the rest of the medical team plummeted.
From Bell's point of view, however, although the patient died, the
experiment was a success. Discounting his failure to locate Garfield's
bullet, Bell patented his machine, which he described the following
summer to the American Association for the Advancement of Science
as "Electrical Experiments to Determine the Location of the
Bullet in the Body of the Late President Garfield and upon a Successful
Form of Induction Balance for the Painless Detection of Metallic
Masses in the Human Body" (my italics). The nation hailed his
patriotism. In November 1882, the Supreme Court of the District
of Columbia
granted the Scottish inventor American citizenship.
An
unacknowledged competition was underway in the last decades of the
nineteenth century between the domestication of sound and of light.
With the invention and almost instant commercialization of the telephone
in 1876, sound seemed to take the lead. For the first time in history,
the human voice could be transmitted miles from the mouth of the
person speaking. Edison's phonograph, in 1877, was an accomplishment
of a different order of magnitude.
The phonograph was the first invention to capture a transient sensual
experience, the first, it seemed, to conquer time. After listening
to a demonstration, the writer Edward Bellamy published a short
story in Harper's Monthly, "With the Eyes Shut." Bellamy's
hero, traveling west by train from Boston and unable to read because
of motion sickness, is rescued from boredom by a vendor renting
gadgets uncannily like a modern Walkman, complete with earphones.
The traveler listens to a book as he watches the passing scene and
then discovers, after arriving in remote Colorado, that everyone
in Denver is
walking around with these gadgets in their ears. Moreover, in the
short time since they had become "listeners," these westerners
had forgotten how to read and write. Bellamy suggests that hearing
is the sense of the future, and coming none too soon to rescue eyesight,
which "was indeed terribly overburdened previous to the introduction
of the phonograph, and now that the sense of hearing is beginning
to assume its proper share of work, it would be strange if an improvement
in the condition of people's eyes were not noticeable."
In
the early 1890s sound seemed to be the door to a technology explosion.
In medicine the stethoscope had become a staple in the physician's
black bag, and percussion of the chest had become a routine method
of sounding out disease. The possibilities of recording sounds on
a phonograph inspired other writers of futuristic fiction as well
as psychologists and linguists. (In 1900 the Anthropology Society
of Paris founded a "glossophonographic" museum, and the
Vienna Academy of Science started a phonographic archive.) Neither
Bellamy nor any of his contemporary fantasists predicted the technological
possibilities of sight. They did not foretell moving pictures, and
they certainly did not imagine a machine that could take pictures
through solid matter, much less penetrate human skin to get a picture
of the bones beneath.
There is no reason they should have. The idea that rays exist that
penetrate the body had been around for ages. As far back as the
thirteenth century the philosopher Roger Bacon had noted that "no
substance is so dense as to prevent rays from passing. The rays
of heat and sound penetrate through the walls of a vessel of gold
or brass." There were also spiritual rays that emanated from
the body to the outside world, portrayed by artists as the spectacular
halos painted around the heads of saints and the holy family. But
nowhere did artist or philosopher suggest that any rays, whether
passing from the outside in or emerging from the soul out through
the skin, could reveal everything beneath the skin to the human
eye, much less leave an impression on something else, like a shadow
on a wall or a permanent imprint on glass or film.
What
appears to be the only recorded prediction came in a talk delivered
to a small group of physicians in Philadelphia in 1872 when the
physician James Da Costa satirized the state of medicine by describing
a future in which "Dr. Magnet, who is a very accomplished physicist,
steps forward: `If you will permit me, I will make you transparent.'
And by means of a modified, portable Ruhmkorff coil [a kind of generator],
and an instrument with lenses dexterously passed into the stomach,
the fair patient is really rendered transparent."
Looking
back, it is hard to understand how deeply opaque the world, and
the human body, seemed to everyone before 1896. This was an era
when heavy window drapes were drawn each night and lace curtains
hung during the day to shield those inside from the eyes of strangers.
This was a world where men and women wore several layers of clothing
in all seasons and entered the ocean to swim covered from neck to
knee. Clothes concealed the skin, and the skin concealed the secrets
of the heart. It was a world where full-length mirrors were a luxury,
and few people ever saw, much less examined, their own naked bodies.
Skeletons, which could be seen only after death, quite reasonably
symbolized death. It is a historical irony that the discovery of
rays that could penetrate clothing and skin and leave an image of
living bones appeared in the most inhibited period in Western history,
an era whose name Victorian has become synonymous with extreme sexual
repression and bodily shame. This era was drawing to a close in
the mid-1890s, and the discovery of X-rays was one of the nails
in the coffin of Victorian prudery.
Getting
Pictures
The
opacity of the Victorian world found validation in photography,
a technology that had evolved slowly through the course of the nineteenth
century. Conceptually, the idea of capturing images on film or glass
was a continuation of the age-old human predilection for capturing
portraits in paint, pen, or, for the less facile, of tracing silhouettes.
Because of the time necessary to get an impression on the earliest
photographic plates, the subjects of these portraits look frozen,
like children playing "statues." People posed, and although
the discomfort was probably negligible in comparison to having to
return for repeated sittings for paintings, sitters may have felt
that, rather than help capture an instant of time, they had been
asked to hold time still. The first photographic efforts involved
chemists who discovered how to capture images on emulsion-covered
paper or glass by using a camera obscure, a box with a pinhole to
admit light, which had served as a draftsman's aid since the days
of Da Vinci.
Major
advances occurred almost simultaneously in France, where Joseph
Niepce and a painter, Louis Daguerre, "fixed" an image
from a camera obscure by adding mercury to the silver compounds
already in use, and in England, where the chemist Fox Talbot fixed
his images on sensitized paper. Talbot, inspired by Daguerre, also
invented a way of getting a positive print from a negative without
destroying the negative. Talbot's techniques offered a convenient
alternative to the cumbersome glass plates that photographers had
had to soak in liquid emulsions immediately prior to exposure whenever
they wanted to take pictures.
When
dry plates entered the market in the 1870s, photography became simple,
cheaper, and more commercial. By the mid-1880s, Kodak was selling
a camera that amateurs could use. Photographers began recording
images that had theretofore been too small, too fast, or too far
away to see and capture. By adapting cameras to microscopes and
telescopes, they got pictures of subjects as remote in size from
each other as human sperm and Saturn's rings. By the 1890s photographs
had become the standard recorders of objective scientific truth.
Clever photographers soon developed "slow motion" imagery
that enabled naturalists and physiologists to document movement
too rapid for the human eye. "Chronophotography" (developed
independently by the physiologist Etienne-Jules Marey in France
and the artist Eadweard Muybridge in the United States) used multiple
pictures to record action, either with a set of cameras that took
pictures in rapid sequence, or with a single camera that snapped
pictures rapidly. Both approaches produced a series of images that
could be analyzed mathematically.
Glass
plates still produced the clearest pictures, but celluloid film
was becoming popular for cheap cameras: it was lightweight, more
convenient, and flexible enough to move quickly across the lens
to produce a series of motion-study shots. These series of overlapping
images became a convention, first among artists like Picasso and
Braque, whose images sometimes look like double exposures but are
often serieslike as has become the standard among comic strip artists.
Movements that could be slowed down, frame by frame, by photographers
could equally well be speeded up to simulate real-time motion. The
challenge of creating moving pictures was taken up simultaneously
by several inventors. Which one succeeded first is still a matter
of controversy. The French have two candidates: Marey, and Auguste
and Louis Lumiere. Americans favor Muybridge and Thomas Edison.
Marey (who had earlier invented a sphygmograph, a device that measured
the pulse by tracing a zigzag line) believed in the superiority
of visual presentations over words. He experimented with moving
pictures by having a single camera take a series of shots rapidly
in succession (as compared to Muybridge, who used a series of cameras
located near each other, which were tripped to snap in rapid sequence).
Edison's
invention, the kinetoscope, worked like a stereopticon, a favorite
Victorian
parlor toy, in the way it was used by only one person at a time,
who would gaze into the device's eyepiece to see pictures flipping
by so rapidly as to give the impression of a motion picture. The
Lumieres alone produced a combination camera and projector that
displayed a moving picture onto a screen before a hall full of people.
On December 28,1895, they presented the first motion pictures to
an audience at the Grand Cafe on the Boulevard des Capucines in
Paris. Moving photographs on flexible celluloid film were part of
the wonderful world of consumer gadgets that the growing middle
classes enjoyed in the early months of 1896. Americans embraced
the future, delighting in the novelty of capturing their experiences
in tangible form that they could enjoy repeatedly--an evening listening
to operatic arias, snapshots of a summer vacation. On the eve of
the discovery of X-rays, everything was in place: the cameras were
loaded, the projection booth ready to go. But no one was prepared
for a device that would change the face of medicine, law, the arts,
and the way ordinary people perceived their own bodies.
Pure
and Applied Science
When
it happened, the world proved astonishingly receptive to this radical
shift of perception. Overnight, much of what had seemed solid only
the day before was shown to be translucent, even transparent. The
public already respected the scientists who explained the miracle.
They had listened in wonder to the physicists who were exploring
the properties of electromagnetic fields. They had nodded in apparent
understanding as these great men explained the mysteries of invisible
rays and particles. The connection between electricity and magnetism
had been summarized mathematically by the 1860s by the British physicist
James Clerk Maxwell in a set of equations that expressed theoretically
the experimental facts about electricity and magnetism acquired
in the preceding decades by giants like Faraday, Henry, and Ampere.
The solution of Maxwell's equations implied the existence of electromagnetic
waves that would propagate from a point just like the
water waves that ripple away from a center when a pebble is plunked
in a pond.
Calculations
predicted that these waves would travel at the speed of light, a
prediction that suggested to a number of physicists that light waves
might be electromagnetic waves, too. A favorite experiment among
the mid-1890s physicists was to send currents through small, pear-shaped
glass tubes under various conditions. One very popular tube had
been designed by an English chemist, William Crookes, in 1876. A
Crookes tube included a metal plate, or cathode, at one end and
often another metal plate, an anode, at the other end or outside
of the tube. Crookes figured out how to pump most of the air out
of the tube, leaving a near-vacuum inside, which made the cathode
last much longer. When voltage was applied to the plates across
the evacuated tube, particles which were soon dubbed cathode rays
(and would soon be identified as electrons) moved through the tube
in a straight line: the rays made the tube glow and made the wall
opposite the cathode turn green.
The
exploration of electricity, magnetism, and light, which was at the
core of cathode ray research, happened in two different kinds of
places: the research laboratories that entrepreneurial inventors
like Bell and Edison set up in connection with their companies,
and the laboratories at universities.
Researchers
in industrial laboratories were expected to look for practical applications,
while university-based researchers were supposed to be devoted exclusively
to a search for the laws of nature. In fact, a good deal of theoretical
research occurred in industrial laboratories, and practical applications
came out of the universities, laying the foundation for the new
field of electrical engineering. However, a number of academic physicists
adamantly refused to have anything to do with practical research,
and Wilhelm Conrad Roentgen was one of them. Roentgen, familiar
in photographs at the time of his discovery of X-rays as a slim
man with a full black beard, had held a chair in physics at the
University of Wurzburg for seven years in 1895. The son of a Dutch
mother and German father, he had lived in Holland from the time
he was three until he left Utrecht, without a secondary school degree,
in the wake of a confrontation with school authorities over his
refusal to identify a schoolmate who had drawn a caricature of a
teacher. Without a degree, he could not enter a German university
but went, instead, to the new Polytechnic in Zurich. There he got
a diploma in mechanical engineering and became the protege of the
physicist August Kundt, who supervised Roentgen's Ph.D. in experimental
physics and took him to Wurzburg as his assistant. In Switzerland
Roentgen met two of the people who would most influence his life:
Anna Bertha Ludwig, whom he married, and Ludwig Zehnder, a fellow
student who was something of a dreamer and against whose character
and imagination Roentgen would define himself in letters and discussions
for most of his life.
The
Roentgens lived a quiet life in Wurzburg, raising an adopted niece
and enjoying annual hiking vacations in Switzerland. His friends
and family remembered Roentgen on these trips as forever moving
about with a big box camera and a black cloth over his head. He
was a man who always kept visual evidence of where he had been and
of what he had seen. Not surprisingly, he also kept photographic
equipment in his laboratory. On November 8, 1895, Roentgen was fifty
years old, head of his department at the University of Wurzburg,
and hard at work investigating the properties of cathode rays. He
was using several tubes, including a variation of a Crookes tube
designed by a younger colleague, Philipp Lenard. Lenard had found,
using his own refinement of a small aluminum foil window in the
Crookes tube, that some cathode rays escaped through the aluminum
foil window and that he could detect the escaped rays on a fluorescent
screen. The rays would make the screen glow when it was set as far
as eight centimeters outside the tube, but no farther. Lenard's
observations prepared Roentgen for what he was about to see. He
had remarkably sharp vision, and it may have been that his excellent
eyesight allowed him his brilliant insight.
That
particular evening Roentgen, following Lenard's technique, wrapped
the tube in black cardboard to prevent distraction from the interior
luminescence, turned off the lights, and turned on the Ruhmkorff
coil with which he generated electric current. By chance, a cardboard
screen like the one Lenard had used (it was coated with barium platinocyanide,
a fluorescent material used frequently at the time to develop photographic
plates) lay on a chair a few feet away. Once his eyes had grown
accustomed to the dark, Roentgen noticed a soft glow coming from
the screen. (Roentgen was colorblind so did not see that it was
green.) He stopped for a moment. The glow, in the shape of the letter
"A," came from a screen several feet away on which a student
had apparently written after dipping a finger in the liquid barium
platinocyanide. It was the kind of glow he had expected to see if
he had put the screen just a few centimeters from the tube. But
there was nothing he knew of, including Lenard's rays, that could
cause fluorescence at such a distance. Puzzled by the phenomenon
and unable to explain it, he dropped his original plan and began
to investigate the strange luminescence. He disconnected the current
and the fluorescence disappeared. The glow returned with the current.
He repeated the experiment over and over until there was no doubt.
The screen was glowing in response to something emanating from the
tube. Neither cathode rays nor any other rays he could think of
could account for the phenomenon. He checked his equipment and recharged
the tube. The glow recurred. Roentgen explored the phenomenon until
late into the November evening. When he finally went upstairs to
dinner (he lived in the institute) he was so preoccupied and distracted
that almost immediately he returned to his laboratory. He did not
reveal his discovery to his two assistants but spent all of his
time for the next seven weeks alone in his laboratory experimenting
and photographing the results. Legend has it that Frau Roentgen
quietly slipped in with hot meals, then left him to his obsession
as he mumbled that he was working on something so new that the world
would think him mad.
To
Roentgen, science was a calling, an almost religious obligation
to expand knowledge of the natural world. The way to get that knowledge,
he believed, was through experiment, and not by constructing a theory
about the nature of the universe. When in the next months reporters
deluged him with questions about his discovery and asked specifically
what he had thought when he noticed the strange rays, he replied,
"I didn't think, I investigated." This was probably disingenuous,
but it reveals what Roentgen believed he should have done. An experimentalist,
he rejected the notion that scientists begin with a working hypothesis
so that their results fit into a grand system. He detested what
we would call "overarching theorizing," the search for
a unified theory. In a series of avuncular letters to his old classmate,
Zehnder, who kept slipping off the German academic ladder in physics
because he insisted on creating grand hypotheses, Roentgen tried
to get him to change his ways. Roentgen suggested that Zehnder work
as he, himself, had done throughout that crucial November and the
rest of the winter. That is, he should systematically explore a
single phenomenon from every possible angle and with no preconceived
idea as to where it would lead.
Roentgen
started with the remarkable ability of the rays to pass through
opaque objects and leave a mark on a fluorescent screen, and soon
established that they could also leave a shadow of some objects
that were inside the ostensibly opaque ones, such as coins inside
a wooden box. He proceeded to examine the rays methodically with
everything he had on hand in the lab, and anything else he could
get his hands on. He explored their effect on fluorescent materials
and noted that when no rays got through, the image on the fluorescent
plate was dark. When the rays did get through, the plate was white.
When the rays hit a photographic plate, he found, as have all radiographers
since, that he did not have a photographic image of the subject,
but rather, the image of its shadow. These photographs proved crucial.
The
pictures, with which we are so familiar today, provided visual proof
for everything he claimed. He began by measuring the brightness
of the fluorescent screen when he held a book between it and the
Crookes tube, and the brightness of the screen without the interposing
book. There was no difference. He tried to see if the rays would
pass through a slim book, and a thick thousand-page volume; a single
playing card, and two solid decks of cards. All proved transparent
to the rays. So did thick blocks of wood, a sheet of vulcanized
rubber and a piece of tin foil. He separated those substances that
stopped the rays, such as lead, from those they passed through.
Then he held his own hand to the invisible light--and became the
first person in the world to see the shadow of his living bones.
Bones, Roentgen discovered, stopped the rays, as did glass made
from lead. He took out a magnet and found that it could not deflect
these rays as it could cathode rays. Nor would a prism refract the
rays the way a prism would have bent visible light. Roentgen concluded
that the rays were entirely new, and so he dubbed them "X,"
for X the unknown.
As 1895 dwindled away, Roentgen decided it was time to share his
discovery. On December 22, he finally brought his wife, always patient
but now very puzzled, into his confidence. He invited her into his
lab and asked her to lay her hand on a photographic plate, then
focused the rays on her for fifteen minutes. He made multiple prints
of the X-ray of Bertha's left hand, her wedding ring apparently
"floating" around the bone of her finger. Shortly after
Christmas, Roentgen sent a "preliminary" report to be
published in the Proceedings of the Physico-Medical Society of Wurzburg.
He called it "On a New Kind of Rays," and to prove his
assertions, he included several radiographs, one of which was the
picture of Frau Roentgen's skeletal hand. The society would not
meet until after the Christmas holidays, but the report was published
with the date December 28, 1895.
A
mathematics-free paper, it may have been the last to reveal a major
discovery in physics that was accessible to the general public.
What Roentgen had discovered were rays invisible to the eye. Research
by many physicists over the next twenty years would reveal that
X-rays are electromagnetic waves of very short wavelength--between
.01 and 10 nanometers (one millionth of a meter). By comparison,
visible light, which, as had been suspected, also turned out to
be an electromagnetic wave, has a characteristic wavelength between
3,500 and 8,000 angstroms, an angstrom being equal to .0001 nanometers
or .0000000001 meters. Later research would show that, like visible
light, X-rays can be understood as a stream of particles, called
photons, but that X-ray photons are far more energetic than the
photons of ordinary light. In Roentgen's day, what most characterized
X-rays was their obvious ability to penetrate and pass through opaque
objects and to leave an impression on a photographic plate. Whenever
an X-ray encounters a photosensitized plate or film, it leaves a
minute black dot. When an X-ray picture is takenof a subject, millions
and millions of X-rays are aimed at it. Some of the rays will make
it all the way through in a straight line, from the cathode raytube,
through the subject, to leave their black imprint on the plate.
But most of the rays do not have such a direct path.
Some X-rays are stopped entirely when they encounter a substance
that absorbs them. A white spot on the plate records their failure
to get all the way through. This white image is, in effect, the
shadow of the object that absorbed the X-rays. Lead will absorb
all the rays, and other metals and bone will absorb a great many,
so they show up as white silhouettes on the radiographs. Rays that
are stopped and absorbed along the way are said to be attenuated.
Still other rays ricochet off tissue and bounce off in random directions,
to hit the film somewhere off their original straight path. These
make gray blurs on the film and decrease the contrast of the attenuated
rays. The proportion of attenuated rays to random rays is what is
known as the signal-to-noise ratio. The signal is the recording
of a real image; the noise is the proportion of exposed surface
of the plate that has been hit by random rays. Even in the simple
X-rays made at the end of the nineteenth century, researchers noticed
the confusing blurs and began trying to figure out how to enhance
contrast. The effort to improve the signal-to-noise ratio has been
a major preoccupation of imaging technology ever since. Many people
initially dismissed X-rays as a mere adjunct to photography.
The
English biologist Alfred Russel Wallace mentions them in The Wonderful
Century, a book he published in 1901 summing up the nineteenth century's
accomplishments, only to dismiss them as a curious photographic
trick. Roentgen resented this assessment, but the photographic record
was crucial to the rapid acceptance of X-rays. Without what we now
call a radiograph, there would have been no dramatic evidence of
the discovery.
Roentgen
acknowledged the value of the camera to his investigation. "In
order to find a law connecting transparency with thickness,"
he kept taking pictures. Eventually he concentrated on the human
body, for the rays penetrated layers of clothing, hair, and flesh
and kept going, blocked only by calcium. That is why they left the
shadow of bones on the photographic plate.
When
on New Year's Day, 1896, Roentgen slipped several copies of the
Proceedings into the mail, he included the radiographs that had
accompanied hisoriginal submission. He sent them to the great scientists
of his day, which to Roentgen meant Arthur Schuster and Lord Kelvin
in Britain, the mathematician Henri Poincare in France, as well
as to his friends Zehnder in Leipzig and Franz Exner, a former colleague
who was then director of the Physical Institute in Vienna. (No one
in North America received a reprint.) Exner showed the paper and
pictures at an informal meeting of a group of
physicists, one of whom, Ernst Lechner, mentioned it to his father,
who edited the Viennese newspaper, the Neue Freie Presse. Recognizing
a good story, the senior Lechner ran it on the front page on Sunday,
January 5, 1896. The text was fine; the illustrations, especially
Frau Roentgen's hand, caused a sensation. A British reporter in
Vienna cabled the story to London where it appeared the next day
in the Chronicle, and from there the news traveled, complete with
picture, to newspapers across the continent and across the Atlantic.
The
response astonished Roentgen. He became an instant celebrity. Within
days of the Viennese paper's scoop on January 5th, X-rays won headlines
wherever newspapers were printed. The reprints Roentgen mailed on
New Year's Day took on a life of their own. A copy, hastily translated,
reached the New York Sun on January 6 and the St. Louis Post-Dispatch
the following day. Four days later it was picked up by the New York
Times and on the twelfth of January by the Times of London, which
had initially dismissed the news as some minor advance in photography.
By
January 31 Roentgen's description of the rays, translated into English,
was published in Science magazine. On February 22, Electrical World,
a popular magazine for amateurs, inventors, and engineers, announced
that there wasn't a Crookes tube to be bought anywhere in Philadelphia.
X-ray fever remained throughout all of 1896, during which 49 serious
books and 1,044 papers were published, as well as cartoons, verse,
and anecdotes galore about the wondrous new rays.
The excitement pushed Roentgen into the spotlight. He patiently
explained his discovery to the press and within a month was able
to give visitors a well-rehearsed tour of his lab and a demonstration
of the rays.
But
his own interest in X-rays was almost exhausted. He published a
second paper on March 9, 1896, and final reflections in May 1897
in "Further Observations on the Properties of the X-Ray."
He then left the subject forever. He could not, however, regain
his privacy. Honored in his homeland, he rejected the offer of a
title but did accept the directorship of the Physical Institute
in Munich, where he moved in 1900 and remained for the rest of his
life. He was honored by scientific societies in England and France
as well, and when the Swedish industrial giant Alfred Nobel left
part of his fortune to endow prizes for outstanding scientific accomplishment,
Roentgen received the first prize awarded in physics, in 1901. The
Nobel honor was marred by discord. The acrimonious Philipp Lenard
never forgot that Roentgen had borrowed one of his tubes in 1894,
or that Roentgen had not acknowledged Lenard's role in developing
some of the techniques that led to the discovery. Lenard had been
exploring fluorescence using cathode rays before Roentgen, even
seeing the same strange glow, and he had published the results of
his research in October 1895. The difference was that Lenard had
neglected to pursue its origins, or to document the phenomenon with
photographs. For years after the discovery, Lenard insisted that
X-rays were simply a kind of cathode ray with new properties, and
not a different phenomenon, and in this he was wrong.
Whatever
they were, Lenard demanded credit for their discovery. Some glory
came his way: throughout 1896 X-rays were often referred to as "Lenard-Roentgen
rays," and the two physicists shared English and French prizes.
But Lenard wanted more than equal billing; he wanted first credit.
During celebrations at Glasgow University in the summer of 1896,
one of Lenard's defenders maintained that the whole thing had been
in Lenard's mind all the time. To which one of his British hosts
reportedly replied that Lenard may have had Roentgen rays in his
own brain, but Roentgen got them into other people's bones. Indeed,
we know now that when the first Nobel Prize was being considered,
the committee put forward both names for a shared prize, but the
academy, whose reasoning process is unknown, chose to honor Roentgen
alone. Further fueling Lenard's fury was the decision in the German-speaking
world to rename X-rays "roentgen rays," and the proliferation
of elaborations on Roentgen's name, calling the pictures "roentgenographs"
or "roentgenograms," and practitioners "roentgenologists."
In
1901 Roentgen recoiled at Lenard's rancor. He could not know that
Lenard's reaction, if extreme, would be emulated many times, if
not as blatantly, in the coming years by other image-making entries
in the Nobel sweepstakes. Lenard received a Nobel Prize of his own
in 1905 for his work with cathode rays. but he still smarted at
what he considered the initial snub and used the platform in Stockholm
to denounce their 1901 decision. For the rest of his life he discredited
Roentgen whenever he had the chance, and Roentgen became so embittered
that he left orders for all of his papers concerning X-rays before
1900 to be burnt, unopened, after his death in 1923. Lenard lived
another twenty-four years. As one of Hitler's pet laureates during
the Third Reich, Lenard denounced not only Roentgen, who was not
Jewish, but all other physicists who, Jewish or not, he accused
of doing "Jewish science." In his last interview in 1945
he still complained that the X-ray had been his "baby"
and that Roentgen had been only the "midwife, the mechanism
of its birth."
The
intervening years have brought evidence that Lenard's was not the
only near miss. Earlier still in 1890 at the University of Pennsylvania,
the physicist Arthur Goodspeed had demonstrated the properties of
a Crookes tube to a visiting photographer who had left a couple
of coins atop a pile of unexposed photographic plates. When the
photographer later developed the plates, he had found them fogged
with two small circular shadows. Unable to explain the images, he
filed them away, only to remember them six years later. Goodspeed
always claimed that the first roentgenograph was, thus, taken unknowingly
in Philadelphia on February 22, 1890. Roentgen's plate had also
been exposed to X-rays by chance, but, whether or not his excellent
vision contributed to his success, his accomplishment was more than
a matter of a chance observation. Roentgen's genius lay not merely
in noticing the new phenomenon, but in the experimental manner in
which
he documented graphically and in clear, simple phrases observations
that would otherwise have seemed incredible.
The
discovery of X-rays marked the beginning of a new epoch in science
and medicine. They provided a tool with which physicists would explore
the structure of matter, and doctors the interior of the human body.
On a different level, they shifted the scales of the senses, making
visual images, which they helped redefine, the dominating venue
for exchanging information in the new century.
© 1997 Bettyann Holtzmann Kevles All rights reserved. ISBN:
0-8135-2358-3
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