Woodcut illustration from an edition of 1833 (13th year of Daoguang reign period of Qing dynasty). The image and text give an account of the principles of diseases treated with decoction of Radix Puerariae (gegen tang), and the therapeutic effects of the individual ingredients of this remedy. Radix Puerariae decoction is made from cassia twig decoction with the addition of ephedra (mahuang) and Radix Puerariae. It is used to treat diseases simultaneously involving the taiyang channel and yangming channel. When wind-cold attacks the foot taiyang channel, the symptoms are headache, stiff neck and backache. Thus ephedra is used to help the cassia twig bring about a sweat, to nourish and protect the taiyang channel. When wind-cold attacks the foot yangming channel, the symptoms are sore eyes, a dry nose and pain along the brow ridge. These symptoms are treated with Radix Puerariae in conjunction with cassia twig, to eliminate malign Qi from the channel at the level of the muscles and bodily surface.
The recipe also contains Chinese herbaceous peony (shaoyao), which is acidic in sapor, to harmonise nutrient Qi; Chinese dates (dazao), which are sweet,to assist protective Qi; fresh ginger, which is pungent, and has a dispersive, supportive and protective effect on the muscles; and liquorice, which is sweet, to harmonise the Centre and regulate the relationship between exterior and interior.