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Ge Gen (Radix Puerariae, 4 liang) Ma Huang (Herba Ephedrae, 2 liang, removed nodes) Gui Zhi (Ramulus Cinnamomi, 2 liang, removed bark) Shao Yao (Radix Paeoniae Rubra or Radix Paeoniae Alba, 2 liang, washed with wine) Gan Cao (Radix Glycyrrhizae, 2 liang, honey-fried) Sheng Jiang (Rhizoma Zingiberis Recens, 3 liang, sliced) Da Zao (Fructus Jujubae, 12 pieces, torn open).

The above seven ingredients. Coarsely crushed. Boil in ten dou of water. First decoct Ma Huang and Ge Gen, reduce by two dou, skim off the foam. Add the remaining herbs. Decoct to obtain three sheng of liquid. Strain off the dregs. Take one sheng warm. Cover with blankets to induce a slight sweat; there is no need to drink hot porridge. The rest of the nursing care and dietary restrictions follow the method of Guizhi Tang (Cinnamon Twig Decoction). This treats Taiyang Shang Han (Cold Damage of the Taiyang Channel), where the pathogen has transmitted to Yangming but has not yet left Taiyang. Therefore, Ge Gen is used as the Jun herb (sovereign herb). Ma Huang is added to Guizhi Tang, still belonging to the simultaneous treatment of Taiyang and Yangming, and is not the principal formula for the Yangming channel. Thus, the classic states: In Taiyang Bing (Disease of the Taiyang Channel), if there is stiffness and discomfort in the nape and back, accompanied by sweating and aversion to wind, Guizhi Jia Ge Gen Tang (Decoction of Cinnamon Twig plus Pueraria) is indicated. If there is stiffness and discomfort in the nape and back, without sweating and with aversion to wind, Gegen Tang (Pueraria Decoction) is indicated. This clearly distinguishes whether the pathogen comes from Wind (Zhong Feng) or Cold (Shang Han) based on the presence or absence of sweating. Whenever a Yangming symptom appears, Ge Gen alone is used to urgently attack the Yangming pathogen, while the residual Taiyang pathogen is still treated with Gui Zhi and Ma Huang, distinguishing between Wind and Cold. If Taiyang and Yangming are affected simultaneously without distinction of priority, the Taiyang pathogen merges with the food and fluids in the Stomach (Yangming) and rushes downward, inevitably causing Xia Li (diarrhea). Gegen Tang is still indicated because it contains Ma Huang and Gui Zhi, which jointly attack the Taiyang pathogen. It is a great error for modern practitioners to mistakenly regard Gegen Tang as a medicine for the Yangming channel.

To the original Gegen Tang formula, add Ban Xia (Fructus Pinelliae Preparatus, half sheng). The washing and decoction methods remain the same.
When Taiyang and Yangming are affected simultaneously (He Bing), diarrhea will inevitably occur; Gegen Tang is indicated. If there is no diarrhea but only vomiting, Gegen Jia Ban Xia Tang (Pueraria Decoction plus Pinellia) is indicated. Among these simultaneous affections, there are differences between those dominated by Wind and those dominated by Cold. Yu Jiayan stated: Wind is Yang, and Yang nature tends to ascend; thus, when affecting Yangming, the fluids in the Stomach rebel upward. Cold is Yin, and Yin nature tends to descend; thus, when affecting Yangming, the food and fluids in the Stomach rush downward. Rushing downward causes diarrhea; using only Ge Gen is sufficient to resolve the pathogen and stop the diarrhea. Rebelling upward causes vomiting; adding Ban Xia is necessary to clear phlegm-fluids and stop vomiting. This demonstrates that the formulas formulated by the ancient Sages do not use any herb arbitrarily.