[Historical investigation on herbal and medical literatures of processing and effect of Rehmanniae Radix].

The radix of Rehmannia glutinosa has been applied to medicinal use since ancient times, and has been called Kiou in the Han dynasty and has been classified by prepared methods, with each preparation given a different name. There were Syoujiou, Kanjiou and Zyukujiou etc. The first was introduced in the Sinnou-honzoukyou and the first and second had been used to prepare some prescriptions contained in the Kinki-youryaku and so on. The third began to appear on the medical and herbal literatures from the Tang period to the early Song. The Rehmanniae Radix has been used as the main material of Hokyoyouketu prescriptions, and by the use of Zyukujiou, their efficacy was regarded to be particularly stronger than the others. The preparation of Hatimigan recorded in the Kinki-youryaku had been used in Kanjiou but was later replaced with Zyukujiou. We should rethink about the quality and process of Chinese herbs on the pharmacy of Kampo medicine.