Number TWO
Six Men on the Streets of London: James Parkinson and the Art of Seeing
An alternative reading of An Essay on the Shaking Palsy (1817)
There is something wonderfully improbable about the origins of Parkinson's disease. In 1817, a London surgeon published a description of a neurological disorder based on six men, including three who were not his patients. Two were strangers he encountered on the streets, while another he observed without conducting a formal examination. From these fragmentary encounters, James Parkinson constructed a disease that physicians still recognize two centuries later.
What deserves attention is not simply his diagnostic accuracy, but the peculiar kind of scientific imagination involved.
Parkinson's achievement depended on seeing time where other observers saw only symptoms. A man with a trembling hand, another with a stooped posture, and a third propelled forward by an increasingly rapid gait might ordinarily have been assigned to different diagnostic categories. Parkinson proposed that they represented different moments in the history of one illness.
This was an audacious intellectual maneuver. He effectively converted six individuals into a longitudinal study, using differences among patients to reconstruct changes occurring within a patient. His evidence was cross-sectional, but his argument was temporal.
The resulting account has an almost cinematic quality. The reader watches a disorder unfold: a slight tremor, initially confined to one hand; increasing difficulty with ordinary activities; altered posture and gait; progressive dependence. Parkinson makes the disease visible by showing what happens next.
There is also something distinctly urban about his discovery. London itself becomes an extension of the examining room. The physician encounters neurological disease not only among those who seek medical attention, but among strangers moving through the city. The streets supply observations that the medical practice alone could not.
Yet this observational freedom carried an important limitation. Parkinson could recognize patterns of movement without reliably establishing their causes. He could infer progression without following every patient through its course. And he could describe a syndrome without knowing whether all six men shared the same underlying pathology.
Modern medicine, with its biomarkers, imaging, diagnostic criteria, and molecular classifications, has not entirely escaped this problem. We continue to debate whether clinically similar patients have one disease, several diseases, or different biological routes to a common phenotype.
Indeed, Parkinson's own disease has become an example of that uncertainty. The familiar clinical syndrome encompasses substantial variation in progression, cognition, autonomic dysfunction, and underlying pathology. Even the boundaries of Parkinson's disease remain subjects of scientific discussion.
Perhaps the deepest lesson of the 1817 essay is that diseases are not simply found in nature, already labeled and waiting to be discovered. They become recognizable when an observer identifies meaningful relationships among otherwise disconnected facts.
Parkinson did not possess the tools to explain the disorder he described. What he possessed was an extraordinary ability to recognize its narrative.
He saw six men. He imagined one disease moving through time. And medicine has spent the following two centuries investigating the biological reality behind that imaginative act.
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FIRST ESSAY - SECOND VERSION OF IT
James Parkinson's 1817 Essay: The Discovery of a Disease and the Defense of an Idea
A modern reading of An Essay on the Shaking Palsy
In 1817, James Parkinson published a small book about a disease that had no name, no established place in medical classification, and no known anatomical basis. He had observed six men, three of them outside his own practice, and believed that their various afflictions represented different stages of a single progressive disorder. He was sufficiently persuaded to publish his conclusions, but sufficiently uncertain to spend much of his preface explaining why he had done so.
It is an unusually attractive beginning to a medical discovery. Parkinson was not announcing a breakthrough, much less proclaiming a revolution. He was asking other physicians to look more closely at something he believed they had been overlooking.
The history of medicine offers plenty of examples of innovators who expected a hostile reception. Harvey had challenged the prevailing account of circulation; Pasteur would later overturn familiar explanations of fermentation and infection. Parkinson's problem was somewhat different. He was not so much challenging an established theory as proposing that a collection of familiar symptoms belonged together. Tremor was well known. So were stooped posture, difficulty walking, and involuntary movements. What was new was the suggestion that these were not separate complaints but successive expressions of one disease.
Parkinson understood that the distinction mattered. A physician who saw only tremor might prescribe for tremor. A physician who recognized the beginning of a progressive illness might think differently about prognosis, treatment, and the urgency of intervention.
An Argument Built Around Its Own Weaknesses
The preface is perhaps the most revealing part of the book. Parkinson acknowledges that his account rests partly on conjecture and analogy rather than the anatomical evidence he regards as the proper foundation of pathology. He knows perfectly well what is missing. He has no autopsies establishing a characteristic lesion, no experimental confirmation, and only a handful of clinical histories.
Rather than conceal these deficiencies, he makes them part of his argument. The disease is sufficiently serious, and its early manifestations sufficiently easy to overlook, that publication may encourage physicians with greater opportunities to investigate it. He hopes particularly for anatomical examination.
There is something admirable about this position. Parkinson does not confuse the strength of his observations with the strength of his explanation. He believes he has recognized a clinical pattern; he is much less certain why it occurs. His willingness to separate these propositions is one reason the essay remains readable long after its anatomical speculations have been discarded.
The book itself follows an orderly progression. Parkinson defines the disorder, describes its course, presents his cases, examines earlier medical literature, proposes a possible anatomical explanation, and considers treatment. The arrangement is deliberate. Each section addresses a different obstacle to accepting the existence of the disease.
The earlier literature is especially important. Parkinson was not the first physician to describe shaking, festination, or disturbances of voluntary movement, and he makes no such claim. His task is to show why the existing descriptions, although individually accurate, had failed to capture the relationship among these phenomena.
Six Patients and the Passage of Time
The six cases would scarcely satisfy the evidentiary expectations of a modern clinical journal. Three men were not Parkinson's patients. Two were encountered in the streets of London, and one was observed without a formal examination. Their histories were incomplete, their examinations inconsistent, and their eventual pathological diagnoses unknowable.
Yet the descriptions are often wonderfully precise. Parkinson notices the asymmetry of early tremor, the increasing difficulty of ordinary movements, the peculiar acceleration of gait, and the discrepancy between a patient's intentions and his body's performance. He describes men who wish to walk at an ordinary pace but find themselves hurrying forward, struggling to keep their feet beneath them.
The familiar clinical picture emerges not from any single patient but from the relationship among the six. Parkinson arranges observations made at different moments in different lives into a proposed sequence of deterioration.
That reconstruction is both the essay's greatest strength and an important source of uncertainty. He could not know that every patient would necessarily pass through the stages he described. Some of the men may have had disorders that would now be classified separately. Nevertheless, the clinical progression he imagined was sufficiently coherent to become the foundation of a recognizable syndrome.
It is easy to underestimate the originality of this achievement. Medical discoveries are often pictured as the identification of something previously invisible: a microorganism, an anatomical lesion, a biochemical abnormality. Parkinson's discovery required no new instrument. It required a new arrangement of things that physicians could already see.
The Anatomy of a Mistake
When Parkinson turns from clinical description to anatomical explanation, the essay becomes less successful, although perhaps more interesting.
He proposes that the disease arises in the upper cervical spinal cord, with involvement extending toward the medulla oblongata. His reasoning depends partly on the apparent preservation of intellect and sensation. If the mind remains clear, he reasons, the principal disturbance may lie below the structures responsible for higher cerebral functions.
The conclusion is wrong. Modern accounts place degeneration of dopaminergic neurons in the substantia nigra and dysfunction of broader neural networks near the center of Parkinson's disease, although its pathology extends well beyond a single structure.
Still, Parkinson's mistake is instructive. He was reasoning from the available clinical evidence toward an anatomical location, much as later neurologists would do with considerably better knowledge of the nervous system. The problem was not that he neglected anatomy. It was that he took a limited understanding of neurological function as the framework within which his observations had to fit.
His assertion that intellect remains unaffected also illustrates the hazards of defining a disease from a small and selected collection of patients. Cognitive impairment, psychiatric symptoms, and autonomic dysfunction are now recognized as important parts of Parkinson's disease, although their expression varies greatly.
There is a certain irony here. Parkinson's clinical observations proved more durable than the anatomical reasoning he used to explain them. The disease survived the theory.
Treatment Before Understanding
The final chapter turns to treatment, and the modern reader encounters the familiar medical armamentarium of the early nineteenth century: bloodletting, blistering, and the production of discharging sores near the presumed site of disease.
These recommendations are difficult to read without wincing. Yet Parkinson's reasoning is neither casual nor indifferent to suffering. If the disease begins as a localized pathological process and progresses to irreversible damage, he argues, intervention might succeed early even when treatment of advanced cases is hopeless.
The therapeutic proposals follow naturally from the anatomical hypothesis. Unfortunately, an internally consistent treatment can be entirely ineffective when its underlying model is mistaken.
Parkinson also understood that recognition of the earliest manifestations was essential. By the time the characteristic disorder was unmistakable, opportunities for useful intervention might already have passed. That concern remains familiar to anyone working on neurodegenerative disease today.
What Parkinson Actually Discovered
There is a temptation, when reading old medical literature, to divide its contents into two categories: observations that anticipated modern science and errors that later science corrected. This is satisfying but not particularly illuminating. It turns the history of medicine into a competition in which the present always wins.
Parkinson's essay is more interesting when read on its own terms. He was working in a medical world where diseases were increasingly understood as processes with characteristic histories and anatomical causes, but where the means of establishing those causes remained rudimentary. He brought together clinical observation, existing medical classifications, anatomical speculation, and a sense of therapeutic urgency. The resulting argument was incomplete, sometimes mistaken, and remarkably productive.
The most consequential part was not his proposed location of the lesion, or even his description of tremor. It was his decision to treat a sequence of changing symptoms as evidence of a single underlying process.
That decision raises a question that medicine has never entirely resolved. When do several symptoms constitute one disease? When does one apparent disease turn out to contain several? Modern molecular pathology has repeatedly forced physicians to divide familiar clinical entities into distinct biological categories, just as clinical observation sometimes brings apparently unrelated manifestations together.
Parkinson's disease itself remains subject to such questions. Patients sharing its characteristic motor syndrome may differ considerably in cognition, autonomic involvement, progression, and pathology. Whether future classifications will preserve today's boundaries is not certain.
James Parkinson could not have anticipated the biological discoveries that would follow his essay. But he recognized something more fundamental about clinical medicine: that the meaning of an observation often depends on its relationship to other observations, including those separated from it by years.
He saw a disorder taking shape across six lives. His explanation was wrong in important particulars, but the pattern he recognized was real enough to outlive him by two centuries.
That is a substantial achievement for a surgeon who began by apologizing for the inadequacy of his evidence.
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FLECK AND PARKINSON - WHAT IS A DISEASE
The separation of syphilis and gonorrhea became broadly established in European medicine between about 1830 and 1850, with Philippe Ricord's work in Paris providing the decisive clinical evidence in the 1830s. Bacteriology supplied a more definitive etiological distinction between 1879 and 1905.
Your reference to Ludwik Fleck is especially apt. In Genesis and Development of a Scientific Fact (1935), Fleck uses the history of syphilis to show that a disease is not simply a preexisting object waiting for physicians to recognize it. Its identity emerges through changing clinical concepts, laboratory techniques, and what Fleck calls thought collectives.
A remarkably long process of separating two diseases
Period | Development |
|---|---|
1500s–1700s | Syphilis and gonorrhea were often grouped under broad concepts of venereal disease. |
1767 | John Hunter's famous inoculation experiment appeared to support a single venereal poison. |
1793 | Benjamin Bell argued that gonorrhea and syphilis were distinct diseases. |
1830s | Philippe Ricord's clinical investigations established the distinction much more convincingly. |
1879 | Albert Neisser identified the gonococcus, the organism responsible for gonorrhea. |
1905 | Fritz Schaudinn and Erich Hoffmann identified Treponema pallidum, the agent of syphilis. |
The extraordinary story of John Hunter
The episode involving John Hunter is particularly revealing.
In 1767, Hunter inoculated material believed to be gonorrheal discharge into a human subject, traditionally said to be himself. The subject subsequently developed a chancre and manifestations of secondary syphilis.
Hunter interpreted this as evidence that gonorrhea could develop into syphilis—that they were manifestations of one disease.
Modern historians believe the donor probably had both infections. Furthermore, whether Hunter actually performed the inoculation on himself is disputed. His published account describes the recipient in the third person.
An experiment intended to settle a controversy instead reinforced the wrong disease classification for decades.
Ricord's decisive intervention, 1831–1838
Philippe Ricord (1799–1889), working at the Hôpital du Midi in Paris, undertook an extensive program of clinical investigation and inoculation experiments.
Between 1831 and 1837, he performed more than 2,500 inoculations using material from patients' lesions. His 1838 Traité pratique sur les maladies vénériennes helped establish that gonorrhea and syphilis were distinct entities.
These experiments would be ethically unacceptable today, but they were influential in resolving the longstanding controversy.
The Fleck connection—and the Parkinson connection
Fleck's argument is subtler than simply saying that physicians made mistakes until better experiments arrived.
He argues that the very concept of syphilis emerged gradually from a heterogeneous collection of genital lesions, skin disorders, constitutional symptoms, and moral assumptions about sexuality. The disease acquired increasingly precise boundaries through successive transformations of medical thinking.
This suggests a fascinating contrast with James Parkinson.
Parkinson (1817): Six apparently different clinical presentations were assembled into one disease.
Ricord (1838): Presentations long grouped together under venereal disease were separated into distinct diseases.
Fleck (1935): The historical processes of combining and separating observations became evidence for a general theory of how scientific facts develop.
The biological distinction between syphilis and gonorrhea was real all along. But the medical categories through which physicians recognized that distinction were historically constructed.
That is the particularly useful Fleckian insight: the natural world constrains disease classification, but it does not tell physicians in advance where to draw every boundary.
And this remains relevant to Parkinson's disease today. Are the various phenotypes of Parkinson's manifestations of one underlying disease, or are we grouping several biological diseases under one clinically useful name?
The distinction between clinical syndromes and etiologically defined diseases remains as important in 2026 as it was in 1838. END
For a primary source, see Fleck's Genesis and Development of a Scientific Fact (1935), especially Chapter 1, How the Modern Concept of Syphilis Originated.
