Theory of diseases treated with Five Drugs and Poria powder

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 Five Drugs and Poria powder (wuling san), and the therapeutic effects of the individual ingredients of this remedy. When external syndromes of the taiyang channel are not alleviated, malignance (xie) travels along the channel into the viscera and heat combines with water. Therefore the external symptoms are headache and stiff neck and the internal symptoms are lack of thirst and difficulty in urination. It is treated with cassia twig, which, being pungent and warm, has a sudorific and dispersing effect, and dispels malign Qi at the exterior level; and also with Five Drugs and Poria powder, which has a diuretic and heat-relieving effect, and dispels fire from the internal organs.

When malign Qi lingers within the taiyang channel, one has a persistent headache, fever and stiff neck. Cassia twig is then used. Accumulated water turns to heat, and hot Qi rises up as steam, which necessarily leads to fever. The bladder is the internal organ of the taiyang channel; the malignance enters the home organ, which is obstructed by fire, leading to difficulty in urination, therefore Five Drugs and Poria powder (wuling san) is used.