In 1120, a Muslim doctor was on his way to see his patient, the Almoravid ruler of Seville. By the side of the road he saw an emaciated man holding a water jug. The man's belly was swollen, and he was in obvious distress. "Are you sick?" the doctor asked. The man nodded.

"What have you been eating?"

"Only a few crusts of bread and the water from this jug."

"Bread won't hurt you," said the doctor. "It could be the water. Where are you getting it?"

"From the well in town."

The doctor pondered a moment. "The well is clean. It must be the jug. Break it and find a new one."

"I can't," whined the man, "This is my only jug."

"And that thing bulging out there," replied the doctor, pointing to the man's midsection, "is your only stomach. It is easier to find a new jug than a new stomach."

The man continued to protest, but one of the doctor's servants picked up a stone and smashed the jug. A dead frog spilled out with the foul water.

"My friend," the doctor said to the patient, "look what you have been drinking. That frog would have taken you with him. Here, take this coin and go buy a new jug."

When the doctor passed by a few days later, he saw the same man sitting by the side of the road. His stomach had shrunk, he had gained weight, and his color was back. Seeing the doctor, the man heaped praise on him.

-attributed to Ibn Abi Usaybi'a, 13th century

While this demonstration of clear reasoning was taking place in Muslim Spain, medical practice in Christian Europe, hobbled by a mindset that would have seen the doctor's work as a challenge to divine will, offered the sick little more than prayers and comfort, rather than medicine or treatments.

In the East, the spread of Islam, beginning in the seventh century CE., sparked the assimilation of existing knowledge and its development in all branches of learning, including medicine. Arab conquerors rapidly absorbed much from their new subjects. Arabic became to the East what Latin and Greek had been to the West-the language of literature and of the arts and sciences, the common tongue of learned men from the Rann of Kutch to the French border-and the Hajj, or pilgrimage to Makkah, brought hundreds of thousands of pilgrims together each year, facilitating the exchange of ideas, knowledge and books.

Recognizing the importance of translating Greek works into Arabic to make them more widely available, the Abbasid caliphs Harun al-Rashid and his son, al-Ma'mun, sponsored a translation bureau in Baghdad-the Bayt al-Hikmah, or House of Wisdom-starting in the late eighth century, that sent agents throughout Muslim and non-Muslim lands in search of scholarly manuscripts in every language. Rendered into Arabic, these precious documents established a solid foundation for the Muslim sciences, not the least of which was medicine.

ken welsh / alamy

Illustrations of surgical instruments from a 13th-century Arabic copy of al-Zahrawi's On Surgery.

As in Greece, medicine in the Muslim world was based on the theory of the four humors that had been advanced by the second-century Greek physician Galen. Each of the four universal elements that comprised the world-earth, air, fire and water-was associated with one of the humors-blood, phlegm, black bile and yellow bile-whose various mixtures defined the different temperaments. When the body's humors were in correct alignment, a person was healthy; when out of balance, he was sick. The task of the doctor, Galen wrote, was to restore this alignment by prescribing changes in diet, exercise or certain activities, or by taking other measures. For example, fever was caused by too much blood, and thus he prescribed bloodletting to remove the excess.

However incorrect, Galen's essentially rationalist view of health and disease found favor in the East, where the Qur'an assured that "for every disease there is a cure." Thus Muslim physicians saw themselves as healers and preservers of health rather than passive witnesses to events with supernatural causes.

While the translators in the House of Wisdom toiled, Muslim doctors developed the bimaristan-later simply maristan-the forerunner of today's hospital. Open to all, it welcomed patients to be treated for, and recover from, a variety of ailments and injuries, including mental illness. The larger maristans were attached to medical schools and libraries, where prospective physicians were taught, examined and, as today, licensed. The maristan became the cradle of Islamic medicine and the means of its dissemination throughout the empire.

Like the hospital, pharmacy as a profession is also an Islamic innovation. In the maristans, trained pharmacists prepared and dispensed remedies that more often than not had some positive effects. Their extensive pharmacopeias detailed the geographical origins, physical properties and methods of application of everything found useful in the curing of disease. By al-Ma'mun's time, the pharmacists (saydalani) were, like doctors, licensed professionals required to pass demanding examinations, and to protect the public from errors and incompetence, government inspectors monitored the purity of their ointments, pills, elixirs, confections, tinctures, suppositories and inhalants. In the maristan, the chief pharmacist held a rank equal to that of the chief of medicine.

But while Abbasid Baghdad, with the House of Wisdom and the first maristans, may have begun the golden age of Islamic medicine, the center of learning and progress began to shift westward in the eighth century, to al-Andalus, today's southern Spain.

national library of medicine

By the time this woodcut showing followers of Albucasis (as Al-Zahrawi was known in Latin) was produced in 1516 in Spain, his medical legacy was already more than 500 years old.

The Abbasids had taken power from the Damascus-based Umayyad dynasty. Abdulrahman, grandson of the 10th Umayyad caliph, escaped the massacre of his relatives and in 758 ce took asylum in Spain. Within a few years, this intrepid ruler had carved out a rival caliphate with its capital at Cordoba, and by the late 10th century Cordoba had surpassed Baghdad as the center of intellectual activity in the Islamic world.

Cordoba's 70 libraries, 900 public baths, 300 mosques and 50 maristans were available to all of its one million residents. Cordoba's university, founded in the eighth century, was a premier center of learning, and its library held at least 225,000 volumes. (At that time, the library of the University of Paris held some 400 volumes.) It drew scholars from all over Europe-one of them, Gerbert of Aurillac, later became Pope Sylvester ii, who replaced cumbersome Roman numerals with today's "Arabic" numbers. Al-Andalus was soon home to accomplished and innovative philosophers, geographers, engineers, architects and physicians.

In the western caliphate, doctors differed from their eastern counterparts. Although Cordoba and Baghdad were in close contact intellectually, the western physicians exhibited more independence of thought than their more classics-bound eastern colleagues, offering no blind obedience to either Galen or the Canon of Ibn Sina, the 10th-century Bukhara-born physician who was the Arab world's equivalent of Aristotle and Leonardo. Instead, they challenged and rejected both when their own experience justified it. Their writings and research showed their preference for the concise, the brief and the exact, as contrasted with the discursive, often hair-splitting, subtleties preferred by the savants of the East.

While the western Islamic world produced hundreds of insightful and even brilliant medical men between the ninth and 15th centuries, five stand at the pinnacle of medicine during their eras, and their influences reverberate even now, more than a millennium later.

"The Father of Surgery"

Born in 938 ce just north of Cordoba in Al Zahra, the royal city of Abdulrahman iii, Abu al-Qasim Khalaf ibn al-'Abbas was known to contemporaries as al-Zahrawi, and his name was Latinized to Albucasis. While little is known for certain about his personal life, his surgical acumen was unprecedented.

On the Cutting Edge A list of major surgical procedures that Al-Zahrawi describes reads like a compendium of medicine in itself. Among his "firsts" were: Exposure and division of the temporal artery to relieve certain types of headaches Extraction of cataracts Guillotine tonsillectomy (as opposed to the more painful snare or ligature methods) Tracheotomy Using a hook to extract a polyp from the nose The supine posture for childbirth (now known as "Walcher's position") Application of ligature for bleeding vessels Treatment of anal fistulas Reduction of a dislocated shoulder (centuries before European techniques) Removal of thyroid cysts Thyroidectomy Mastectomy to treat breast cancer Surgery for breast reduction

musee atger / giraudon / bridgeman art library

Al-Zahrawi's annotated illustrations of surgical instruments were circulating in Europe in Latin translation in the 14th century.

Al-Zahrawi only wrote one book, Kitab al-Tasrif li-man 'Ajizja 'an al-Ta'lif (The Arrangement [of Medical Knowledge] for One Who is Unable to Compile [a Manual for Himself]), a compendium of 30 volumes on medicine, surgery, pharmacy and other health topics compiled during a 50-year career. Its last volume, the 300-page On Surgery, was the first book to treat surgery as a separate subject and the first illustrated surgical treatise. Covering ophthalmology, obstetrics, gynecology, military medicine, urology, orthopedics and more, it remained a standard surgical reference in Europe until the late 16th century.

Al-Zahrawi described a vast repertoire (see "On the Cutting Edge," at left) of procedures, inventions and techniques, including thyroidectomy, extraction of cataracts and an innovative method of removing kidney stones by diversion through the rectum that dramatically reduced the mortality rate for the procedure, compared to the method Galen recommended.

The Arrangement of Medical Knowledge was the earliest text to deal with dental surgery in detail, including reimplantation of dislodged teeth. It also described the carving of false teeth from animal bone, as well as how to correct non-aligned or deformed teeth. Al-Zahrawi also detailed procedures still used by today's dental hygienists to remove calculus deposits from teeth.

More prosaically, al-Zahrawi used ink preoperatively to mark the incisions on his patients' skin, now a standard procedure worldwide. He was the first to use catgut for internal sutures, silk for cosmetic surgery and cotton as a surgical dressing. He described, and probably invented, the plaster cast for fractures-a practice not widely adopted in Europe until the 19th century. He produced annotated diagrams of more than 200 surgical instruments, many of which he devised himself. His meticulous illustrations, intended as both teaching tools and manufacturing guides, are the earliest known and possibly the first ever such published diagrams. His best-known inventions were the syringe, the obstetrical forceps, the surgical hook and needle, the bone saw and the lithotomy scalpel-all items in use today in much the same forms.

The Doctor of Seville

The doctor who observed, diagnosed and cured the man by the side of the road at the beginning of this article was Abu Marwan 'Abd al-Malik ibn Zuhr, later Latinized to Avenzoar, who was born in 1091 ce in Seville. Since the Banu Zuhr, as his family was known, had already produced two generations of physicians (and would produce five more), there was no question about his career.

Ibn Zuhr, however, did not merely follow in his ancestors' footsteps. He became the first Muslim scientist to devote himself exclusively to medicine, and his several major discoveries were chronicled in his books Kitab al-Taysir fi 'l-Mudawat wa 'l-Tadbir (Practical Manual of Treatments and Diets) and a treatise on psychology whose title translates Book of the Middle Course Concerning the Reformation of Souls and Bodies, as well as Kitab al Aghdiya (Book on Foods) that describes the health effects of diets, condiments and drinks.

In this body of work, one of his smaller but most effective accomplishments was proof that scabies is caused by the itch mite, and that it can be cured by removing the parasite from the patient's body without purging, bleeding or any other (often painful) treatments associated with the four humors. This discovery sent a shudder through medical science, for it unshackled medicine from strict reliance on the theory of humors and, with that, blind acceptance of Galen and Ibn Sina.

Ibn Zuhr also wrote about how diet and lifestyle can help a person avoid developing kidney stones. He gave the first accurate descriptions of neurological disorders, including meningitis, intracranial thrombophlebitis and mediastinal tumors, and he made some of the first contributions to what became modern neuropharmacology. He provided the first detailed report of cancer of the colon. Ibn Zuhr was the first to explain how to provide direct feeding through the gullet or rectum in cases where normal feeding was not possible-a technique now known as parenteral feeding.

Ibn Zuhr introduced the experimental method into surgery, using animals as test subjects-using, for example, a goat to prove the safety of a tracheotomy procedure he devised. He also performed post-mortems on sheep while doing clinical research on how to treat ulcerating diseases of the lungs. Ibn Zuhr is the first physician known to have performed human dissection and to use autopsies to enhance his understanding of surgical techniques.

bibliotheque de la faculte de medicine / archives charmet / bridgeman art library (detail)

This 15th-century Italian illustration depicts the presentation of a work by Ibn Zuhr of Seville, translated into Latin by John of Capua.

Ibn Zuhr established surgery as an independent field by introducing a training course designed specifically for future surgeons before allowing them to perform operations independently. He differentiated the roles of a general practitioner and a surgeon, drawing the metaphorical "red lines" at which a physician should stop during his management of a surgical condition, thus further helping define surgery as a medical specialty. He was also among the first to use anesthesia, performing hundreds of surgeries after placing sponges soaked in a mixture of cannabis, opium and hyoscyamus (henbane) over the patient's face.

Not least, by seeing to it that both his daughter and his granddaughter went into medicine, he became a pioneer in a different way. Though largely limited to obstetrics, these women began a tradition in the Muslim world that accepted females as medical doctors 700 years before Johns Hopkins University graduated the first American female physician.

Doctor and Philosopher

Born in Cordoba in 1126 and at one time a student of Ibn Zuhr, Abu 'l-Walid Muhammad ibn Ahmed ibn Muhammad ibn Rushd was in many respects to the western caliphate what Ibn Sina was to the eastern one. Known in Europe as Averroes, he became known mainly for his works on philosophy. Ibn Rushd's principal medical work, a slender volume called Kitab al-Kulliyat fi al-Tibb (General Rules of Medicine) became an important prcis of medicine. Beginning with a brief anatomical survey of the human body, the book continues with sections on the functions of the various organs, systemic diseases, diet, drugs, poisons, baths and the role of exercise in maintaining health. The sections on surgery briefly cover the treatment of abscesses and the use of styptics, cauterization and ligatures. Perhaps most notably of all, he observed that smallpox "is a disease (that) attacks the patient only once"-the first known reference to acquired immunity.

Doctor in Exile

Musa ibn Maymun (Latinized to Maimonides) was a Renaissance man before there was a Renaissance. He too was born in Cordoba, just 12 years after Ibn Rushd, to a family that had produced eight generations of scholars. The towering genius of his era, a Jew living in a Muslim world, his achievements covered law, philosophy and medicine. At an early age, he developed an interest in science and philosophy. In addition to reading the works of Muslim scholars, he also read those of the Greek philosophers made accessible through Arabic translations. His great work on Jewish law was written in Arabic using the Hebrew alphabet, and as a religious scholar he opposed the mingling of religion and medicine. He was the only intellectual of the Middle Ages who truly personified the confluence of four cultures: Greco-Roman, Arab, Jewish and European.

nathan benn / alamy

This bronze bust of Maimonides is in Cordoba, where he was born.

When he was 10 years old, the less-than-tolerant Almohads conquered Cordoba. They offered the city's Jews and Christians the choice of conversion to Islam, exile or death. Maimonides's family chose exile, and they eventually settled near Cairo. When family tragedy reduced them to penury, he took up the practice of medicine.

Maimonides wrote 10 known medical works in Arabic. They describe, among much else, conditions including asthma, diabetes, hepatitis and pneumonia. They emphasize moderation and a healthy lifestyle. A doctor, he wrote, must be knowledgeable in many disciplines, treat the whole patient and not just the disease, heal both the body and the soul, and must himself be imbued with human and spiritual values, the foremost of which is compassion.

Throughout his medical works Maimonides often challenged what he called Galen's "arrogant presumption" when it differed from his own experiences, leading to one of his key contributions: the idea that, in medicine, personal empirical experience trumps written authority. Nonetheless, his passion for order and learning led him to abridge the Roman physician's massive literary output to a single book of key extracts that a physician could carry in his pocket. Though he was also a Talmudic rabbi, when it came to the understanding of disease, Maimonides was what today we would call a "natural scientist"-a strict empiricist-and he strove to clearly divorce medicine from religion. At a time when magic, superstition and astrology were all widespread in medical practice, his writings contain no references to these, nor to Talmudic medicine. That which is correct, he argued, is that which works.

Maimonides taught that individuals should look after their own health by avoiding bad habits and seeking medical attention promptly when ill. "One's attention," he wrote, "should first focus on the maintenance of natural [body] warmth, before anything else. That which best insures this is [the performance of] moderate physical exercise, which is good both for the body and soul." He then goes on to prescribe a daily regimen of walking for elderly patients, something with a distinctly modern ring to it. He also discusses the benefits of massage and touch as a means of stimulating the innate "heat" of the body, insofar as it rejuvenates the body naturally.

He recognized furthermore the medical benefits of positive thinking, leading to an early form of psychosomatic medicine. Whether certain amulets or trinkets were anathema to his rational world view was unimportant compared to the needs of the patient. If they made the patient feel better, he wrote, then having them present was best "lest the mind of the patient be too greatly disturbed."

Secrets of the Heart

By the time Ala al-Din Abu al-Hassan Ali ibn Abi-Hazm al-Qurashi al Dimashqi -far more easily known as Ibn al-Nafis-was born in 1213 in Damascus, the intellectual center of the Islamic world had become Ayyubid-ruled Cairo. While in his early 20's, Ibn al-Nafis moved there and eventually became chief physician at the 8000-bed Al-Mansouri Hospital.

behzad / musee d'histoire de la medicine / archives charmet / bridgeman art library

This modern gouache illustration depicting Ibn al-Nafis is titled "Discovery of the 'Small Circulation'"-the movement of blood from the right ventricle of the heart to the lungs and back to the left atrium. It was Ibn al-Nafis who first correctly described the interaction of the heart and lungs in circulation and oxygenation of blood.

At 29, he published the Sharh Tashrih al-Qanun Ibn Sina (Commentary on Anatomy in the Canon of Ibn Sina). The book described a number of his anatomical discoveries, including the earliest explanation of the pulmonary circulation of blood.

Ibn al-Nafis went on to show that the wall between the right and left ventricles of the heart is solid and without pores, thus disproving Galen's teaching that the blood passes directly from the right to the left side of the heart. Ibn al-Nafis then correctly stated that the blood must pass from the right ventricle to the lungs, where its lighter parts filter into the pulmonary vein to mix with air and then to the left atrium and finally onward to the rest of the body. It was the first time anyone was able to explain how air entered the blood.

musee atger / giraudon / bridgeman art library (detail)

In a 14th-century French version of al-Zahrawi's Arrangement of Medical Knowledge, a sick man and a crippled man are presented to a doctor. Al-Zahrawi's compendium was used in Europe till the late 16th century.

Ibn al-Nafis also hinted at the existence of capillary circulation, arguing "there must be small communications or pores [manafidh] between the pulmonary artery and vein." Though his hypothesis was limited to blood transit in the lungs, it would be confirmed for the entire body 400 years later when Marcello Malpighi described the action of capillaries. Moreover, after the 14th century, Ibn al-Nafis's discovery was lost, and it was not until 1924, when Egyptian physician Muhyo al-Deen Altawi found a copy of the Commentary in Berlin's Prussian State Library, that the full extent of Ibn al-Nafis's work was understood-showing that it was he, and not William Harvey some four centuries later, who had discovered the circulatory system.

Unfortunately, Ibn al-Nafis's fall into undeserved obscurity was not unique or even particularly unusual. Over those medieval centuries Muslim physicians by the tens of thousands, the great and the ordinary, lived and worked mostly outside centers of medical science. While they toiled, small groups of Christian and Jewish scholars also labored, filling for a coming era the roles of translators and disseminators that their Muslim predecessors had once filled for al-Ma'mun in Baghdad. Many were located along the porous, shifting, multicultural frontier with Spain where Toledo, Barcelona and Segovia offered them support; others gathered in the cities of France, Italy and Sicily that were touched by Islam. They too became cultural bridges, returning to a reawakening West both the intellectual foundations it had foregone nearly a millennium earlier and a rich legacy of discovery upon which today's western medicine is founded.

The physicians who produced this legacy of discovery in the Muslim world devised techniques and further unraveled enduring mysteries of the human body and mind. They established hospitals and the professions of surgery, medicine and pharmacy, invented surgical instruments and applied empirical methods to test hypotheses. They separated religion from science and opened a door for women. Many of their precepts of personal health, diet and hygiene are common sense today. Perhaps most important of all, they re-taught European physicians that sickness is only a deviation from health, and that the role of medicine is to cure disease.

If any of this seems too easily self-evident to us, that is because progress turns yesterday's discoveries into today's everyday knowledge.

This article appeared on pages 34-39 of the January/February 2011 print edition of Saudi Aramco World.