Illuminating the Invisible: The Pioneers Who Taught Us to See Beneath the Skin

In my work as a human osteologist, much of what I study has already been laid bare by time. Bone survives after the softer structures of the body have disappeared, preserving evidence of growth, disease, injury and lived experience. As a soft tissue therapist, however, I encounter anatomy very differently: through movement, resistance, posture and touch. One discipline examines what remains; the other works with the living body.

Medical imaging forms a remarkable bridge between these two perspectives. It allows us to look beneath the surface without disturbing it—to examine internal structure while the body remains whole.

It is easy to take that ability for granted. A modern radiograph can be produced within seconds. A CT scanner can reconstruct the body in cross-section and generate detailed three-dimensional images. Yet little more than a century ago, the interior of a living person remained largely inaccessible. Physicians could observe the surface, listen to the chest, palpate tissues and infer what might be happening beneath the skin, but definitive knowledge often required surgery or post-mortem examination.

That changed during the winter of 1895, when a faint glow appeared in a darkened laboratory in Würzburg.

A Light That Should Not Have Been There

On 8 November 1895, Wilhelm Conrad Röntgen was working alone at the University of Würzburg, investigating the behaviour of electricity inside a partially evacuated glass tube. Cathode-ray experiments were attracting considerable scientific attention, but the equipment was temperamental: glass vessels, electrical coils, wires and fluorescent materials arranged across laboratories that often looked closer to workshops than the highly controlled research environments we know today.

Röntgen had enclosed his tube in black cardboard so that no visible light could escape. When he activated the apparatus, however, he noticed a fluorescent screen some distance away beginning to glow.

It should have remained dark.

The cathode rays being studied were not thought capable of travelling through the intervening air. Yet something had escaped from the covered tube, crossed the room and caused the screen to fluoresce. Röntgen did not immediately announce that he had discovered a new form of radiation. Instead, he began to test what he had seen.

For several weeks, he worked with an intensity that reportedly left little room for anything else. He placed different materials between the tube and the fluorescent screen. Paper and cardboard barely impeded the unknown rays. Wood and flesh allowed some of them to pass, while denser substances such as metal and bone cast stronger shadows. Objects hidden inside boxes became visible. Weights enclosed within wooden cases emerged as ghostly silhouettes.

The original observation had been unexpected, but the discovery itself was not simply a lucky accident. It was the product of Röntgen recognising that something did not fit existing expectations and then pursuing that anomaly with disciplined curiosity.

Because he did not yet know what the radiation was, he called it X-Strahlen—X-rays—using the mathematical symbol for an unknown quantity (Röntgen, 1896; Glasser, 1959).

Then came the image that would capture the public imagination.

In December 1895, Röntgen placed the hand of his wife, Anna Bertha, between the apparatus and a photographic plate. When the plate was developed, the flesh of her hand appeared as a pale shadow. Inside it, unmistakably, were the bones of her fingers and the darker outline of her wedding ring.

It is difficult now to recover how unsettling that image must have seemed. This was not a skeleton uncovered by excavation or exposed during dissection. It was the skeleton of a living woman, made visible while her hand remained intact.

For physicians, the possibilities were immediately apparent. A fracture might be located without exploratory surgery. A bullet or fragment of metal could be found inside the body. Diseases affecting bone and joints might be recognised before death. The boundary between the body’s visible exterior and its concealed interior had suddenly become permeable.

The Unlikely Route to Würzburg

Röntgen’s arrival at this moment was far from inevitable.

As a young man in Utrecht, he had been expelled from school after being accused of producing a caricature of a teacher—an accusation he denied. Because he lacked the usual leaving certificate, conventional university admission was difficult. His path into science might easily have ended there.

Instead, he gained entrance to the Federal Polytechnic Institute in Zürich by examination. He initially trained in mechanical engineering before moving towards experimental physics, receiving his doctorate from the University of Zürich in 1869.

That engineering background mattered. Röntgen was not merely interested in abstract physical principles; he understood apparatus, materials and the practical behaviour of machines. His later discovery emerged from that combination of theoretical curiosity and mechanical competence.

News of the new rays spread with extraordinary speed. Röntgen submitted his first paper, “On a New Kind of Rays”, in December 1895. Within weeks, accounts of the discovery were appearing internationally, and researchers and medical practitioners were reproducing his experiments. X-ray equipment began entering hospitals before anyone fully understood either its capabilities or its dangers.

In 1901, Röntgen received the inaugural Nobel Prize in Physics. He did not patent his discovery, believing that its benefits should be freely available. He neither sought nor accumulated the fortune that such a patent might have produced.

By then, however, X-rays had already begun to escape the confines of physics laboratories. Physicians were not content merely to reproduce Röntgen’s shadowy images. They wanted to know what else this new way of seeing might reveal.

One of the people asking that question was working in Glasgow.

John Macintyre and a Body in Motion

John Macintyre was a physician and surgeon at Glasgow Royal Infirmary, but he was also deeply interested in electricity, engineering and photography. This unusual combination placed him among the small number of early doctors capable of understanding both the medical potential of X-rays and the machinery required to produce them.

In March 1896, only a few months after Röntgen announced his discovery, Macintyre secured support for an X-ray facility at Glasgow Royal Infirmary. It is commonly described as the first dedicated hospital X-ray department in the world, although claims of priority during this rapidly developing period are not always straightforward.

Macintyre quickly began applying radiography to real clinical problems. In one early case, he used X-rays to identify a stone in a patient’s kidney; its presence was subsequently confirmed during surgery. The rays were no longer merely a scientific curiosity. They could alter diagnosis and guide treatment.

Yet a radiograph had an obvious limitation: it arrested the body at a single moment.

A joint might be photographed, but not seen articulating. The thorax might be examined, but the rhythm of breathing was lost. The heart could cast a shadow, but a still image could not capture its continuous movement. The living body was being rendered visible, but it was being rendered motionless.

Macintyre began wondering whether the emerging technologies of radiography and cinematography could be brought together.

This was an ambitious proposition. Early fluorescent X-ray screens produced only faint images. Photographic materials were relatively insensitive, cameras were cumbersome and each exposure added to the radiation received by the subject and operator. Motion-picture technology was itself still in its infancy.

Nevertheless, in 1897 Macintyre published “X Ray Records for the Cinematograph”, describing attempts to create sequential X-ray images. In one method, a camera photographed an image produced on a fluorescent screen. In another, a strip of sensitive film moved beneath a narrow opening in a lead-covered cinematographic apparatus (Macintyre, 1897).

His subject was modest: the limb of a frog, manipulated so that its knee flexed and extended.

The resulting sequence lasted only a few seconds. To modern eyes it is flickering, indistinct and technically primitive. But its significance lies in what it proposed. Internal anatomy could be recorded not merely as structure, but as movement. The hidden body might be watched as it changed through time.

Macintyre demonstrated his work first in Glasgow and subsequently before a scientific audience in London. Those watching the frog’s bones move across the screen were seeing the beginnings of an entirely new approach to anatomy—one concerned not only with what structures looked like, but with what they did.

The conceptual leap had been made. Turning it into a dependable clinical method would take several more decades.

Between Wonder and Danger

The first generation of radiologists entered a field without an established map. There were no reliable dose limits, no personal monitoring badges and little understanding of the cumulative effects of ionising radiation. The machines themselves offered limited control, and an adequate image might require exposure lasting several minutes.

At first, X-rays seemed almost magical. They were demonstrated in lecture halls and public exhibitions as well as hospitals. Hands, coins and concealed objects appeared on fluorescent screens. Their ability to pass through the body encouraged a sense that a longstanding barrier had been overcome.

Warnings soon followed.

Skin reddening, burns and hair loss were reported within months of the discovery. Practitioners who repeatedly tested equipment on their own hands developed chronic ulceration and tissue damage. Some underwent successive amputations; others later developed cancers associated with prolonged occupational exposure.

These injuries were not marginal to the development of radiology. They changed it. The suffering of early operators and patients gradually forced the profession to confront the fact that seeing inside the body carried a biological cost.

Shielding improved. Exposure times shortened. Instruments were developed to estimate dose. Formal organisations and standards of radiation protection emerged. The modern principles of justification and optimisation—the requirement that an examination should provide a meaningful benefit and that exposure should be kept to what is necessary—grew from this hard-won experience.

The history of X-rays is therefore not simply a procession of technical triumphs. It is also a history of learning to treat an extraordinary discovery with caution.

Russell Reynolds and the Fleeting Image

By the early twentieth century, fluoroscopy allowed a physician to observe the moving shadows of internal structures directly on a fluorescent screen. Unlike a conventional radiograph, which preserved a still image on a plate, fluoroscopy presented movement as it happened.

But the image was faint and transient. Once the examination ended, what the physician had observed survived only in notes, drawings and memory.

Russell J. Reynolds, a British radiologist working during the early decades of the twentieth century, recognised the value of converting that fleeting observation into a permanent record. He began experimenting with cineradiography during the 1920s, building upon the principle Macintyre had demonstrated with the frog’s limb.

The problem remained one of light. Fluorescent screens were not bright enough to be photographed easily, while placing cinematographic film directly in the X-ray beam created practical and radiological difficulties. Reynolds therefore developed an indirect system in which a cine camera recorded the image appearing on a fluorescent screen. A lens with an exceptionally wide aperture gathered as much of the weak light as possible.

His laboratory belonged to a different technological world from Röntgen’s, yet it was still a place of improvised solutions: cameras, screens and X-ray tubes had to be carefully aligned; timing had to be synchronised; and small improvements in optics or exposure could determine whether the resulting film was clinically useful.

In 1934, Reynolds published a detailed account of his apparatus. It could produce moving records of the heart, lungs, thorax and joints—processes that could now be replayed, slowed down and examined repeatedly (Reynolds, 1934).

This transformed the status of the fluoroscopic image. A movement that had previously existed only for the duration of the examination could become part of the clinical record. A film could be shown to other specialists, revisited after treatment or compared with a later study. Internal movement had become something that could be preserved and shared.

Reynolds did not invent fluoroscopy, nor did his apparatus remove its risks. Image quality remained limited, the equipment required careful calibration and radiation exposure was still substantial by modern standards. His importance lies in refinement: he helped carry cineradiography from experimental demonstration towards practical clinical investigation.

That distinction is important. Scientific progress rarely consists of a single isolated moment in which a complete technology springs into existence. More often, it develops through a chain of questions. Röntgen asked what the unknown rays could penetrate. Macintyre asked whether their images could capture motion. Reynolds asked how that motion could be recorded reliably enough to study.

Each worked within the limits of the equipment available to him, and each left the next generation with a more useful way of seeing.

From Shadows to Digital Bodies

Modern medical imaging would be almost unrecognisable to these early pioneers, yet its foundations remain closely connected to their work.

Conventional radiography continues to produce two-dimensional projections of internal structures. Dense mineralised tissue absorbs more X-rays than surrounding soft tissue, allowing bone, calcification and metal to appear particularly clearly. Fluoroscopy provides real-time imaging during investigations of swallowing, digestion and joint movement, as well as during many image-guided procedures.

CT extends the same physical principle much further. Instead of producing a single projection, it measures X-ray attenuation from numerous angles and uses computers to reconstruct the body in cross-section. Those sections can then be combined into three-dimensional representations, allowing internal relationships to be examined without physical dissection.

Ultrasound and magnetic resonance imaging reveal other aspects of living anatomy, often without using ionising radiation. Each technology makes certain tissues and processes visible while leaving others less distinct. No medical image presents the body exactly as it is. It is a translation produced by the interaction between anatomy, energy, machinery and interpretation.

That is particularly meaningful to me as both an osteologist and a soft tissue therapist. A radiograph can reveal a fracture, degenerative change or skeletal alignment, but it cannot fully convey how someone experiences pain or movement. Palpation and functional assessment can reveal patterns of tension and restriction, but they cannot provide an unobstructed view of internal bone. Each perspective contributes something the other cannot.

The real legacy of Röntgen, Macintyre and Reynolds is therefore larger than any individual apparatus. Together, they changed what it was possible to ask of the living body.

Röntgen showed that its concealed structures could be made visible. Macintyre showed that internal anatomy need not remain frozen. Reynolds helped preserve movement so that it could be studied, revisited and shared. Around them, patients, assistants, engineers and other early radiological practitioners participated in a process whose benefits and dangers were not yet fully known.

The next time we look at a radiograph, it is worth pausing before treating it as an ordinary clinical image. Behind it lies a darkened room, a fluorescent screen that should not have glowed, the bones of a living hand, a frog’s knee moving across a strip of film and generations of researchers learning how to illuminate the body without harming it.

What now appears routine began with the courage to look closely at something unexpected—and to ask what else might be hidden in the darkness.

References

Ardran, G.M. (1973) ‘Cineradiography’, British Journal of Radiology, 46(550), pp. 885–888. Available at: https://doi.org/10.1259/0007-1285-46-550-885

Boice, J.D. Jr, Dauer, L.T., Kase, K.R., Mettler, F.A. Jr and Vetter, R.J. (2020) ‘Evolution of radiation protection for medical workers’, British Journal of Radiology, 93(1112), 20200282. Available at: https://doi.org/10.1259/bjr.20200282

British Film Institute (n.d.) ‘First X-ray Cinematograph Film Ever Taken’. Available at: https://replay.bfi.org.uk/video/57b03116-a17f-5252-8bfe-28fb6d9f82ec

British Institute of Radiology (n.d.) ‘1930s diagnostic imaging’. Available at: https://www.bir.org.uk/useful-information/history-of-radiology/1930s/1930s-diagnostic-imaging.aspx

Glasser, O. (1959) Wilhelm Conrad Röntgen und die Geschichte der Röntgenstrahlen. 2nd edn. Berlin, Göttingen and Heidelberg: Springer-Verlag.

Macintyre, J. (1897) ‘X Ray Records for the Cinematograph’, Archives of Skiagraphy, 1, pp. 37–38.

Nobel Prize Outreach (n.d.) ‘Wilhelm Conrad Röntgen: Biographical’. Available at: https://www.nobelprize.org/prizes/physics/1901/rontgen/biographical/

Reynolds, R.J. (1934) ‘Cineradiography’, British Journal of Radiology, 7(79), pp. 415–424. Available at: https://doi.org/10.1259/0007-1285-7-79-415

Röntgen, W.C. (1896) ‘On a new kind of rays’, translated by A. Stanton, Nature, 53(1369), pp. 274–276. Available at: https://doi.org/10.1038/053274b0

Royal College of Physicians (n.d.) ‘Russell John Reynolds’. Available at: https://history.rcp.ac.uk/inspiring-physicians/russell-john-reynolds