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Guizhi (Ramulus Cinnamomi): Flavor is pungent and slightly sweet, nature is warm. Its strength excels in promoting circulation and unblocking, capable of ascending the Grand Qi (i.e., Zong Qi in the chest), descending rebellious Qi (such as Chong Qi or Liver Qi rushing upward), and dispersing pathogenic Qi (such as external contraction of wind-cold). Zhang Zhongjing uses it in Linggui Zhugan Tang to treat shortness of breath, taking advantage of its ascending property; he uses it in Guizhi Jia Gui Tang to treat Ben Tun (rushing pig disease), taking advantage of its descending property; he uses it in formulas such as Mahuang Tang, Guizhi Tang, Da Qing Long Tang, and Xiao Qing Long Tang to treat external contractions, taking advantage of its dispersing property. However, the *Shennong Bencao Jing* discusses Mugui (which is Guizhi), stating at the beginning that it mainly treats cough with rebellious Qi, seemingly regarding the ability to descend rebellious Qi as Guizhi's specialty. Few other materia medica texts mention its ability to descend rebellious Qi, which means using Guizhi while discarding its strengths.

In the original formula of Xiao Qing Long Tang, Guizhi and Mahuang are used together. For cases with wheezing, Mahuang is removed and Xingren is added, but Guizhi is not removed. This is truly because the *Shennong Bencao Jing* originally stated that Guizhi treats "tu xi" (spitting and inhaling, i.e., wheezing); removing Guizhi would fail to stabilize wheezing. Yet physicians all know that Mahuang drains the Lung and stabilizes wheezing, but few know that Guizhi descends Qi and stabilizes wheezing. This is the fault of not studying the *Shennong Bencao Jing*. Guizhi excels at suppressing the excess of Liver Wood so it does not act recklessly, and also excels at regulating the stagnation of Liver Wood so it flows smoothly. Because its flavor is sweet, it also excels at harmonizing the Spleen and Stomach, enabling the sinking Spleen Qi to ascend and the rebellious Stomach Qi to descend. When the Spleen and Stomach are harmonized, retained fluids are naturally eliminated, and accumulated food is naturally transformed. Its power of promotion and unblocking can also guide the San Jiao downward to connect with the Bladder to facilitate urination (contraindicated when urination is difficult due to heat, though sometimes a small amount is added as a guide when using cooling herbs to promote urination). It is contraindicated for those with heat in the Upper Jiao and those who frequently suffer from blood disorders.

Guizhi is neither a diaphoretic nor an antihidrotic. Its power of promoting circulation and surface dispersion rotates between the interior and exterior, able to harmonize Ying and Wei, warm the muscles, and invigorate the blood vessels, thereby allowing wind-cold to resolve spontaneously and numbness to open up. Because its flavor is pungent and sweet, the pungent nature disperses, and the sweet nature tonifies; its function lies between half-dispersing and half-tonifying. Therefore, those who take Guizhi Tang and desire sweating must drink hot porridge, indicating that it cannot induce sweating on its own; if individuals with strong Yang and deficient Yin mistakenly take it, sweat will immediately escape, indicating that it cannot stop sweating.

Note: In the *Shanghan Lun*, when Guizhi is used, it is always noted to be "peeled," which does not mean removing the bark of the branch. The ancients used Guizhi only by selecting fresh young branches from the current year; when broken, the inside and outside were uniform, with bark and wood indistinguishable. If one could distinguish bark from wood, they were discarded and not used, hence the term "peeled." Chen Xiuyuan's nephew, Chen Mingqi, discussed this in detail.

Xu Lingtai stated that those who have contracted wind with heat, if mistakenly given Guizhi, will vomit blood. This is indeed an accurate and appropriate theory. I recall treating an elderly woman in her sixties who contracted wind-cold in early spring. I prescribed a formula for releasing the exterior containing several qian of Guizhi, after which she recovered immediately. Her family, finding the formula effective, pasted it on the wall. By early summer, she caught a cold again and took medicine from that same formula on her own, resulting in hematemesis. She recovered only after treatment by another physician. Presumably, what she contracted previously was cold wind, whereas what she contracted later was warm wind. Thus, the former situation was suitable for Guizhi, while the latter contraindicated it. Those who use Guizhi Tang to treat Warm Diseases should beware! However, although Xu knew that mistaken use of Guizhi could cause hematemesis, his *Huixi Medical Cases* records treating a woman with external contraction complicated by phlegm and wheezing. This patient had a history of blood disorders, recurring intermittently, with slight cough during attacks (based on these words, her blood disorder was likely hemoptysis). Due to severe phlegm and wheezing and urgent condition, he treated the branch first by prescribing Xiao Qing Long Tang, and she recovered.

According to standard practice, when using Xiao Qing Long Tang for external contraction with phlegm and wheezing, Mahuang should be removed and Xingren added. However, in this case, Guizhi should be removed and Mahuang retained. Furthermore, following the method of using Xiao Qing Long Tang in the *Jingui Yaolue*, adding raw Shigao (Gypsum Fibrosum) would be more secure. Both Mahuang and Guizhi can stabilize wheezing, but Guizhi moves the Blood level, whereas Mahuang does not move the Blood level. Therefore, it is appropriate to remove Guizhi and retain Mahuang, and then borrow the cooling and sedating power of Shigao to prevent reckless movement of the Blood. This is the most comprehensive strategy. On that day, Xu used this formula without mentioning modifications; did he omit them, or did he use the original formula? If he used the original formula, although the disease was cured, it was akin to a desperate gamble.