The most interesting features of Japanese medicine are the extent to which it was derivative and the rapidity with which, after a slow start, it became Westernized and scientific. In early times disease was regarded as sent by the gods or produced by the influence of evil spirits. Treatment and prevention were based largely on religious practices, such as prayers, incantations, and exorcism; at a later date drugs and bloodletting were also employed.
Beginning in 608 CE, when young Japanese physicians were sent to China for a long period of study, Chinese influence on Japanese medicine was paramount. In 982, Tamba Yasuyori completed the 30-volume Ishinhō, the oldest Japanese medical work still extant. This work discusses diseases and their treatment, classified mainly according to the affected organs or parts. It is based entirely on older Chinese medical works, with the concept of yin and yang underlying the theory of disease causation.
In 1570 a 15-volume medical work was published by Menase Dōsan, who also wrote at least five other works. In the most significant of these, the Keitekishū (1574; a manual of the practice of medicine), diseases—or sometimes merely symptoms—are classified and described in 51 groups; the work is unusual in that it includes a section on the diseases of old age. Another distinguished physician and teacher of the period, Nagata Tokuhun, whose important books were the I-no-ben (1585) and the Baika mujinzo (1611), held that the chief aim of the medical art was to support the natural force and, consequently, that it was useless to persist with stereotyped methods of treatment unless the physician had the cooperation of the patient.
European medicine was introduced into Japan in the 16th century by Jesuit missionaries and again in the 17th century by Dutch physicians. Translations of European books on anatomy and internal medicine were made in the 18th century, and in 1836 an influential Japanese work on physiology appeared. In 1857 a group of Dutch-trained Japanese physicians founded a medical school in Edo (later Tokyo) that is regarded as the beginning of the medical faculty of the Imperial University of Tokyo.
During the last third of the 18th century it became government policy to Westernize Japanese medicine, and great progress was made in the foundation of medical schools and the encouragement of research. Important medical breakthroughs by the Japanese followed, among them the discovery of the plague bacillus in 1894, the discovery of a dysentery bacillus in 1897, the isolation of adrenaline (epinephrine) in crystalline form in 1901, and the first experimental production of a tar-induced cancer in 1918.