A Philosophy of the Blood and the Bile

Rush dipped his quill and paused over the page. The sentence he had just written insisted that all disease, whatever its apparent form, derived from a single cause: irregular action in the blood vessels. This was not speculation. It was the foundation upon which he had built twenty-five years of practice, thousands of patients, and a reputation that now stood at the center of American medicine.

Outside his window on Walnut Street, the air hung thick and still over Philadelphia. The smell from the docks had grown strange of late—sweet beneath the tar and hemp, like fruit left to rot in a closed room. He had noticed it. He had also noticed the patients who had begun appearing at the Pennsylvania Hospital, at the dispensary he had founded for the poor, and in his private rooms.

Headache, back pain, nausea, skin the color of saffron, vomit the color of coffee grounds. Rush examined them with the attention of a man who had seen fevers before, who had treated refugees from Saint-Domingue the year prior, who had studied under the greatest physicians in Edinburgh. He believed he knew what they suffered from. He also believed he knew how to cure it.

His confidence was not universally shared. The city’s medical establishment had fractured into factions, each loyal to a different theory and a different treatment. Some physicians argued that diseases were specific entities, each requiring a specific remedy. Others clung to older notions of miasmas, bad airs rising from swamps and gutters to poison the constitution. Still others believed in contagion, the idea that sickness passed from body to body through invisible particles. Rush rejected all of these partial explanations. He had built a unified system, a philosophy of the blood and the bile that reduced all illness to a single disorder and all treatment to a single method. The body was a hydraulic machine. Disease was obstruction. The cure was depletion. He was a leading proponent of what was called heroic medicine, firmly believing in such practices as bloodletting patients, as well as purges using calomel and other toxic substances.

Benjamin Rush, not because he was unique, but because he was the most prominent exponent of a medical orthodoxy that would shape Philadelphia’s response to the coming catastrophe. His intellectual foundations mattered. They would determine how the city’s sick were treated, who lived and who died, and how the survivors would remember the epidemic. Rush’s education, his published works, his public stance on bleeding and purging—these were not abstract concerns. They were the preconditions for a tragedy already beginning to unfold in the alleys near the wharves.

Rush had arrived in Edinburgh in the autumn of 1768, a twenty-two-year-old from a modest Philadelphia family. His father had died when he was five, and his education had been funded by relatives who expected him to enter the ministry. He chose medicine instead. The University of Edinburgh was then the finest medical school in the English-speaking world, a center of Enlightenment thought where students learned to distrust ancient authorities and trust their own observations. Rush studied under William Cullen, a physician who had built his reputation on a system of medicine that emphasized the nervous system and the body’s “excitability.” Cullen taught that disease was not a foreign invader but a disturbance in the body’s own powers, a loss of tone that the physician must correct.

The Scottish system appealed to Rush’s temperament. Where older physicians had catalogued symptoms and prescribed complex remedies, Cullen sought general principles that could explain disease across the whole of nature. Rush absorbed this approach but transformed it. Where his teacher focused on the nerves, Rush focused on the blood. He came to believe that the circulatory system held the key to all pathology. The body’s vessels were like the pipes of an organ. When they were too full, the system became diseased. When they were emptied, health returned. The logic was hydraulic, mechanical, satisfying to an Enlightenment mind. It offered a single explanation for every ailment, from common colds to malignant fevers. It also offered a single treatment: remove the excess. Bleed the patient. Purge the bowels. Induce vomiting. Empty the vessels until the body’s tone was restored.

By the time Rush returned to Philadelphia in 1769, he had committed himself to this system. He began to practice, and he began to publish. His first major work, a dissertation on the “natural history of medicine,” argued that physicians should seek general principles rather than accumulating disconnected facts. Ambition and energy drove him. The American Revolution gave him a stage. Rush signed the Declaration of Independence, served as surgeon general of the Continental Army, and used his position to advocate for reforms in military medicine. He also made enemies. His criticism of army hospitals led to a court-martial and his resignation. He returned to Philadelphia, his reputation bruised but intact.

The postwar years were Rush’s most productive. He helped found the College of Physicians of Philadelphia, the first professional medical organization in the new nation. He secured a professorship at the University of Pennsylvania, where he taught the next generation of American doctors. He published essays on everything from alcoholism to yellow fever, from the diseases of slaves to the proper education of children. Reform was his vocation. Medicine, politics, and morality were branches of the same tree. A healthy republic required healthy citizens, and healthy citizens required physicians who understood the laws of nature.

Rush’s medical philosophy was inseparable from his republican ideals. The body was a microcosm of the state. Just as a republic required balance among its branches and vigilance against corruption, the body required balance among its fluids and vigilance against excess. Bleeding and purging were not merely treatments; they were political virtues rendered in medical form. Active, decisive, egalitarian. Any physician could bleed a patient. It required no special drugs, no secret knowledge, only the will to act. Rush despised the passive treatments favored by some of his rivals—gentle diets, rest, waiting for nature to take its course. He called these methods “slothful” and “aristocratic.” A republican physician should intervene. Attack the disease with the same vigor that the patriots had attacked the British.

This rhetoric was not mere flourish. Rush genuinely believed that his methods were democratic, that they stripped medicine of mystification and placed power in the hands of the people. He instructed laypeople to bleed their own family members when physicians were unavailable. He published simplified guides to domestic medicine. Ordinary citizens should understand their bodies and treat themselves. In a republic, every man should be his own doctor—or at least know enough to recognize quackery and reject it. The problem was that Rush’s own methods, by the standards of his time, were not universally accepted. Many physicians considered bleeding dangerous, especially in cases of fever where the patient was already weakened. They preferred stimulants—wine, bark, cold baths—to rally the body’s defenses. Rush dismissed these critics as timid, as men who lacked the courage to act.

The yellow fever epidemic of 1793 would test Rush’s system as nothing had before. But in early August, as the first cases appeared along the waterfront, Rush did not yet know what he faced. He saw patients with fever, jaundice, and black vomit. He recognized the symptoms from his reading and from outbreaks he had studied in previous years. He diagnosed the disease as a “bilious remitting fever”—a category that included what we now call yellow fever but also encompassed other tropical diseases. The name mattered less than the treatment. Rush believed that all fevers, whatever their apparent differences, shared a single underlying cause: inflammation of the blood vessels. The remedy was always the same. Bleed. Purge. Repeat.

He began to treat his patients accordingly. Veins opened, and blood flowed in quantities that shocked his colleagues. Calomel, a mercury compound, induced violent purging. Jalap, a root, acted as a powerful laxative. Patients vomited and defecated until they were emptied. Then he bled them again. The logic was relentless. If the patient improved, the treatment had worked. If the patient worsened, the disease was stronger than expected, and more depletion was required. If the patient died, the treatment had been applied too late. Rush’s system was self-validating. It could not fail; it could only be failed.

Other physicians in Philadelphia watched with alarm. Dr. Adam Kuhn, a rival who had also studied in Edinburgh but had arrived at different conclusions, advocated for stimulating remedies. Wine, bark, and cold baths to strengthen the patient’s constitution. Dr. Edward Stevens, a physician from the West Indies with experience treating yellow fever, recommended gentle purgatives and rest. Rush tried their methods, he later claimed, and found them wanting. His patients died. So he returned to bleeding and purging with renewed conviction. He would later write that he had “tried Kuhn’s and Steven’s stimulating remedies” but that “his patients still died.” The evidence confirmed what he already believed: depletion was the only path to cure.

The dispute among physicians was not merely technical. It reflected a deeper division in American medicine, a struggle over who would define the terms of care. Rush positioned himself as the champion of a distinctly American approach, a republican medicine that rejected European sophistication in favor of bold action. His rivals saw a dangerous dogmatist, a man whose theories had outpaced his evidence. They accused him of killing patients with his excessive bleeding. He accused them of cowardice and complicity with the disease. The conflict would intensify as the epidemic spread, and it would outlast the fever itself. Years later, physicians would still be arguing over Rush’s methods, publishing pamphlets and counter-pamphlets, each side convinced that the other had blood on its hands.

But in August 1793, the epidemic was just beginning, and Rush was the most prominent physician in the city. His authority was institutional as well as intellectual. A professorship at the university. The dispensary that served the poor. Membership in the American Philosophical Society, correspondence with Thomas Jefferson and John Adams, a signature on the Declaration. When he spoke, people listened. And he was speaking constantly now, writing letters, publishing notices in the newspapers, advising colleagues and city leaders. He declared that the fever was present, that it was contagious, that the city must act. He was wrong about the contagion—yellow fever is not transmitted person to person but by mosquitoes—but he was right that the city faced a crisis.

Rush’s errors were built into his system. His unified theory of disease left no room for the specific mechanisms of infection that would not be discovered for another century. The possibility that a mosquito might carry the fever from one body to another lay beyond imagination. He assumed, like most physicians of his time, that the disease arose from local conditions: bad air, rotting vegetable matter, the filth of the docks. He recommended cleaning the streets, draining the swamps, removing the sources of putrefaction. Sensible measures. They would help reduce other diseases. But they would do nothing to stop the yellow fever. The mosquitoes would continue to breed in the water barrels and cisterns that every household kept. They would continue to bite.

The city’s leaders, meanwhile, were slow to recognize the danger. The Board of Health consisted of part-time officials with no real power. No inspectors, no quarantine facilities, no plan for an epidemic. Mayor Matthew Clarkson was a competent man but overwhelmed by the scale of the gathering disaster. The federal government, still headquartered in Philadelphia, had no authority to intervene. The Constitution said nothing about public health. President George Washington was in Virginia for the summer, and his cabinet was scattered. The republic had no mechanism for dealing with plague. It would have to improvise.

Improvisation meant relying on individuals, and no individual was more central than Rush. His philosophy of the blood and the bile would become the city’s de facto policy. Patients would be bled and purged because Rush said so, and because there was no one with the authority or the credibility to challenge him. The results would be catastrophic. Hundreds, perhaps thousands, would die under his care, weakened by blood loss and poisoned by mercury. Some would survive despite the treatment, their bodies fighting off the fever while Rush claimed the victory. The epidemic would expose the limits of Enlightenment medicine, the dangers of dogmatism, and the terrible cost of acting on incomplete knowledge with absolute confidence.

Yet Rush was no monster. Compassion for his patients and his city drove him. During the epidemic, he would work himself to exhaustion, seeing dozens of patients a day, contracting the fever himself and surviving, then returning to work. He refused to flee when so many others abandoned the city. Saving lives was his purpose. That belief was the source of his power and his error. He could not see that his methods were harming because he could not admit that his system was flawed. To doubt himself would be to doubt the entire edifice of his medical philosophy, the foundation upon which he had built his career and his reputation.

The irony was that Rush’s system contained a kernel of truth. Disease was not a supernatural punishment but a natural process, subject to laws that physicians could discover. Public health required collective action—cleaning the streets, draining the swamps, caring for the poor. Medicine should be democratic, knowledge shared. But he was wrong about the specific mechanism of yellow fever, and he was wrong about the treatment. His bleeding and purging would weaken patients precisely when they needed strength, dehydrate them when they needed fluids, poison them when they needed care. His confidence, so admirable in other contexts, became lethal in the face of a disease he did not understand.

Philadelphia in August 1793 stood on the edge of catastrophe, and Benjamin Rush was the man who would lead it over that edge. His medical philosophy, developed over decades and refined through countless disputes, was ready to be applied. The patients were waiting. The bleeding would begin.

The first cases Rush saw were near the docks, among the sailors and dockworkers who lived in crowded boarding houses and worked in the holds of ships from the West Indies. He visited them in their rooms, examined their yellowed skin and black vomit, and pronounced his diagnosis. Veins opened. Calomel and jalap administered. Some recovered. Many died. He recorded the outcomes in his notes, but the notes were not neutral. They were shaped by his expectations. When a patient lived, Rush attributed the recovery to his treatment. When a patient died, he blamed the delay in calling for help, or the severity of the disease, or the patient’s underlying weakness. The system absorbed every result and remained intact.

This was the pattern that would continue through September and October, as the epidemic swelled and the city emptied. Rush would treat hundreds of patients, and he would defend his methods in letters, in newspaper essays, in a book he would publish the following year—his 1794 ‘An account of the bilious remitting yellow fever’. Rival physicians would attack him. Survivors would blame him for the deaths of loved ones. Critics would accuse him of butchery. He would respond with the same confidence that had defined his career. The philosophy of the blood and the bile had served him for decades. It would not fail him now.

What Rush could not see was that his philosophy was part of the problem. His certainty, his refusal to consider alternatives, his conviction that depletion was the answer to every disease—these were not virtues. They were blinders. They prevented him from learning from the epidemic, from adjusting his methods, from recognizing that other physicians might have something to teach. The epidemic would eventually burn itself out, as yellow fever epidemics do, when the first frost killed the mosquitoes. But by then, Rush’s reputation would be damaged, his methods discredited in the eyes of many, and the city littered with bodies. The cost of his confidence would be measured in graves.

Rush’s medical philosophy also shaped the city’s response in another way: it determined who would provide care. Convinced that the fever was contagious—an incorrect belief—Rush argued that nurses were needed to attend the sick amid fierce debates over its cause and potential for contagion. But most white Philadelphians had fled, and those who remained were too frightened to enter infected houses. Rush turned to the Free African Society, founded by Absalom Jones and Richard Allen. He appealed to them directly—they were appealed to by respected physician Benjamin Rush—asking them to organize their members to nurse the sick and bury the dead based on his incorrect belief that people of African descent were immune to yellow fever.

During the 1793 yellow fever epidemic, Richard Allen and Absalom Jones helped to organize free blacks as essential workers to care for the sick and deal with the dead. They were appealed to by respected physician Benjamin Rush. Amid fierce debates over the cause and treatment of the fever, Rush’s endorsement gave legitimacy to the effort, and Allen and Jones mobilized their community. Black Philadelphians worked as nurses, cart drivers, and grave diggers, exposing themselves to the disease and dying in numbers that would later be recognized as disproportionate to their population. Rush’s request, however well-intentioned, rested on a false premise that would cost Black lives.

The alliance between Rush and the Black community would outlast the epidemic, but it would also generate conflict. After the fever subsided, the publisher Mathew Carey would accuse Black nurses of price-gouging and theft, exploiting the sick rather than helping them. Allen and Jones would respond with a pamphlet of their own, defending their community’s honor and documenting their sacrifices. Rush, caught in the middle, would support his Black colleagues but fail to prevent the damage to their reputations. The epidemic would expose not only the limits of medicine but the fault lines of race and class in the new republic.

All of this lay ahead in August 1793. For now, Rush sat at his desk, preparing his lecture, confident in his system, unaware of what was coming. The city around him was hot, crowded, and increasingly anxious. Rumors of fever had begun to circulate, but official denial was still the order of the day. The Board of Health had recorded a handful of deaths, but they had not declared an epidemic. Merchants feared the economic consequences of quarantine. Politicians feared the consequences of panic. Physicians disagreed about the nature of the disease and the proper response. Rush, as always, was certain. A philosophy. A method. Patients to bleed.

The philosophy that Rush carried into the epidemic was the product of a particular moment in the history of medicine. The late eighteenth century was a time of transition. The old humoral theory, which had dominated European medicine for centuries, was giving way to new systems that emphasized the nerves, the blood, the solids and fluids of the body. But the new systems were no more accurate than the old. Physicians could describe symptoms and speculate about causes, but they could not see the microscopic agents that caused disease. They could not measure the physiological processes they claimed to understand. They operated in the dark, guided by theory rather than evidence, and their theories were shaped by their culture, their politics, and their prejudices.

Rush’s system was a product of that transitional moment. It combined ancient ideas about balance with modern ideas about mechanics. Rational, systematic, comprehensive. It was also wrong. The body was not a hydraulic machine. Disease was not simply obstruction. Bleeding and purging did not restore health; they often hastened death. But these truths would not become clear until long after the epidemic had ended. In 1793, Rush’s philosophy was the best that Philadelphia had. It would have to suffice.

The consequences of that philosophy would unfold over the coming months. Written in the death records of the city, in the testimony of survivors, in the polemics that physicians would publish against each other. Shaping not only the epidemic but its aftermath, the way Philadelphians remembered the crisis and assigned blame. Rush would emerge from the epidemic with his reputation battered but not destroyed. He would continue to practice, to teach, to publish. He would defend his methods until his death in 1813. Remembered by some as a hero who stayed when others fled, by others as a dangerous dogmatist whose treatments killed more than they cured.

Rush set down his pen. The lecture was nearly finished. He would deliver it to his students in a few days, and they would carry his words into the city, into the sickrooms, into the lives of people who would live or die by his methods. He did not know that the epidemic was already spreading, that the cases he had seen were the first wave of a deluge, that within weeks he would be treating dozens of patients a day, that his own sister would die, that he would fall ill himself, that the city would empty and the government would flee. He knew only that he had a system, and that the system was true. That was enough. It would have to be.

Outside his window, the street was quiet. The heat pressed against the glass. Somewhere near the river, a child was crying, a woman was praying, a man was dying of a fever that had no name. Rush could not hear them. He was thinking about blood, about bile, about the balance of the body and the duty of the physician. He was thinking about his lecture. He was thinking about the truth, and the truth was that he had found the key to all disease, and the key turned in the lock, and the door was opening, and behind it lay a room full of dying people, and they were waiting for him.