George Sarton in the Introduction to the History of Science says that “Rhazes was the greatest physician of Islam and the Medieval Ages.” The Encyclopedia of Islam remarks that “Rhazes remained up to the 17th century the indisputable authority of medicine.” The Bulletin of the World Health Organization (WHO), May 1970, pays tribute to him by stating that “His writings on smallpox and measles show originality and accuracy, and his essay on infectious diseases was the first scientific treatise on the subject.”

Abu Bakr Muhammad Ibn Zakariya Ar-Razi was born at Ray near modern Tehran in 251 A.H. (864 C.E.) It is said that early in his life al-Razi was interested in singing and music besides other professions. Because of his eagerness for knowledge, he became more interested in the study of alchemy and chemistry, philosophy, logic, mathematics and physics. It was the field of medicine that he spent most of his life, practicing it, studying and writing about it. Due to his fame in medicine he was appointed head of the physicians of the Ray Hospital, and later put in charge of the Baghdad main Hospital during the reign of the Adhud-Daulah.

An interesting episode of Al-Razi‘s remarkable method of choosing the right spot for the Baghdad main hospital is described as follows. When Adhud Daulah asked Al-Razi to build a hospital, he had pieces of fresh meat placed at various parts of the city of Baghdad. Some time later, he checked each piece to find out which one was less rotten than the others, and he chose the spot of the least rotten pieces of meat a site for the hospital.

Ar-Razi was a pioneer in many areas of medicine and treatment and the health sciences in general. In particular, he was a pioneer in the fields of pediatrics, obstetrics and ophthalmology. In medicine, his contribution was so significant that it can only be compared to that of Ibn Sina (Avicenna). Some of his works in medicine, e.g., Kitab al-Mansoori, Al-Hawi, Kitab al-Mulooki and Kitab al-Judari wa al-Hasabah earned everlasting fame. A special feature of his medical system was that he greatly favored cures through correct and regulated food. This was combined with his emphasis on the influence of psychological factors on health. He also tried proposed remedies first on animals in order to evaluate in their effects and side effects. Ar-Razi was the first person to introduce the use of alcohol (Arabic Al-Kuhl) for medical purposes. He was also an expert surgeon and was the first to use opium for anaesthesia.

Ar-Razi was the first to give an account of the operation for the extraction of a cataract and also the first scientist to discuss the pupillary reaction or the widening and narrowing of the pupil of the eye. He explained that the reaction was due to the presence of small muscles which act according to the intensity of light. The current understanding on this subject confirms his work.

The greatest medical work of Ar-Razi (Rhazes), and perhaps the most extensive ever written by a medical man, is al-Hawi, i.e., the “Comprehensive Book,” which includes indeed Greek, Syrian, and early Arabic medical knowledge in their entirety. Throughout his life Ar-Razi must have collected extracts from all the books available to him on medicine. In his last years, he combined these with his medical experience into an enormous twenty volume medical encyclopedia. Al-Hawi was the largest medical encyclopedia composed by then. It was translated into Latin under the auspices of Charles I of Anjou by the Sicilian Jewish physician, Faraj ibn Salim (Farragut) in 1279 and was repeatedly printed from 1488 onwards. Al-Hawi was known as ‘Continens’ in its Latin translation. “By 1542 there had appeared five editions of this vast and costly work, besides many more of various parts of it. Its influence on European medicine was thus very considerable.” (The Legacy of Islam, pp. 323-5). Another scholar points out that Ar-Razi‘s “al-Hawi was one of the nine volumes constituting the whole library of the Paris Faculty of Medicine in 1395.” (Durant; Haider, Bammate, 29).

Kitab al-Mansoori, which was translated into Latin (known by the title ‘Liber Almansoris’) in the 1480s in Milan, comprised ten volumes and dealt exhaustively with Greco-Arab medicine. Some of its volumes have been published separately into German and French. The ninth volume of the translation made by Gerard of Cremona the “Nonus Al-Mansuri,” was a popular text in Europe until the sixteenth century (Durant, p247). Ar-Razi in Al-Mansoori devoted a whole chapter on anatomy. In it he has presented a detailed description of the various organs of the human body, and sensory and motor parts. He has also given elaborate descriptions of the intervertebral foramina and the spinal chord, and correctly asserted that an injury either to the brain or spinal chord would lead to paralysis of the parts of the organs whose nerve supply was damaged or destroyed.

His al-Judari wa al-Hasabah was the first treatise on smallpox and chickenpox, and is largely based on Razi‘s original contribution. It was first translated into Latin in 1565 and later into several European languages and went into forty editions between 1498 and 1866. It was translated into English by William A. Greenhill, London, 1848. Through his treatise Razi became the first to draw clear comparisons between smallpox and chickenpox.

Ar-Razi gave many valuable pieces of advice to practicing physicians: “A physician should not forget to ask his patient all sorts of questions pertaining to the possible causes of his illness, both internal and external….If a physician can treat a patient through nutrition rather than medicine he has done the best thing. A physician should always try to convince his patient of improvement and hope in the effectiveness of treatment, for the psychological state of the patient has a great effect on his physical condition. He used to advise his patients thus: “Whoever seeks treatment with too many physicians might suffer the risk of the faults of each one of them. A patient should restrict consultation to one trustworthy physician.”

Ar-Razi also compounded medicines and took keen interest in experimental and theoretical sciences. It is conjectured that he developed his chemistry independently of Jabir Ibn Hayyan (Geber). He has discussed several chemical reactions and also given full descriptions of and designs for about twenty instruments used in chemical investigations. His description of chemical knowledge is in plain and plausible language. One of his books Kitab-al-Asrar deals with the preparation of chemical materials and their utilization. Another one was translated into Latin under the name Liber Experimentorum. He went beyond his predecessors in dividing substances into plants, animals and minerals, thus in a way opening the way for inorganic and organic chemistry. By and large, this classification still holds. As a chemist, he was the first to produce sulfuric acid together with some other acids, and he also prepared alcohol by fermenting sweet products.

His contribution as a philosopher is also well known. The basic elements in his philosophical system are the creator, spirit, matter, space and time. He discusses their characteristics in detail and his concepts of space and time as constituting a continuum is outstanding.

Ar-Razi was a prolific author, who has left monumental treatises on numerous subjects. He has more than two hundred outstanding scientific contributions to his credit, out of which about half deal with medicine and twenty-one on Alchemy. He also wrote on physics, mathematics, astronomy and optics, but these writings could not be preserved. A number of his other books, including Jami-fi-al-Tib, Maqalah fi al-Hasat fi Kuli wa al-Mathana, Kitab al-Qalb, Kitab-al-Mafasil, Kitab-al-‘Ilaj al-Ghoraba, Bar al-Sa’ah, and al-Taqseem wa al-Takhsir, have been published in various European languages. About 40 of his manuscripts are still extant in the museums and libraries of Iran, Paris, Britain, and Rampur (India). His contribution has greatly influenced the development of science, in general, and medicine in particular.

Like other great scholars of Islamic history, Razi‘s erudition was all-embracing and his scientific work remarkable. The foregoing description represents only a part of the great legacy left by Ar-Razi. He died in 930 C.E. Razi‘s portrait adorns the great hall of the Faculty of Medicine in the University of Paris.