By Li Shi-Zhen
Ma Huang is specific for the Lung channel, and thus treatments for Lung disorders usually include it. Zhang Zhong-Jing used Ma Huang for cold damage with no sweating; if there is already sweating Gui Zhi is used. Over the centuries commentators have simply recorded this insight, but none has so far investigated its essence and subtleties. I, Shi-Zhen, spent considerable time unravelling this in my mind, and seem to have come to an explanation different to that of past writers. And here it is:
Yin fluids and yang fluids (jin ye) make up sweat, and sweat is actually blood. At the nutritive level it is blood, while at the protective level it becomes sweat.
When cold attacks the nutritive level, this nutritive blood becomes bound internally and cannot penetrate outward to the protective level [and therefore there is no sweating]. When the protective is blocked and fixed, yin and yang fluids cannot move, thus [again] there is lack of sweat, fever and aversion to cold. When wind damages the protective level, protective qi drains outward and cannot stand guard by [or contain] the nutritive internally, so the nutritive qi weakens and the yin and yang-fluids lose containment, thus sweating occurs with fever and aversion to wind.
Now both pathogenic wind and cold enter by way of the skin, which is associated with the Lungs. The Lungs govern the protective qi, covering the whole body: the image of Heaven! Although the pattern of disorder belongs to greater yang stage, yet it is the Lungs that truly suffer the brunt of the pathogenic qi. When the symptoms include red face, anger and constraint, cough with phlegm, wheeze with fullness of the chest, is this not Lung disorder?
When the skin and hair are bound externally, then the pathogen attacks the interior, and Lung qi becomes constrained and breathing difficult. Therefore Ma Huang, Gan Cao and Gui Zhi are used to lead the nutritive-level pathogen out to reach the muscle layer of the exterior, and Xing Ren is brought in to assist draining the Lungs to facilitate qi flow. [This is Ma Huang Tang (Ephedra Decoction)].
After sweating, if there is no high fever but still wheezing, then Shi Gao is added — Zhu Gong’s Book to Safeguard Life adds Shi Gao and Zhi Mu after midsummer — all are Lung heat draining herbs [and make up Ma Huang Xing Ren Gan Cao Shi Gao Tang (Ephedra, Apricot Kernel, Gypsum and Licorice Decoction)]. Thus although Ma Huang Tang (Ephedra Decoction) is a powerful greater yang-stage sweat-inducing formula, in fact they are herbs to spread and disperse Lung channel constrained heat.
If the pores and interstices are not tightly closed, then yin and yang-fluids drain outward so that Lung qi is naturally deficient. Deficiency is addressed by tonifying the mother, therefore Gui Zhi and Gan Cao are utilised: externally, to disperse the wind pathogen and rescue the exterior; internally, to cut down Liver Wood and protect the Spleen. Assisting with Shao Yao (Paeonia) drains the Liver and conserves Spleen, draining the East [Liver] thus tonifies the West [the direction of Lungs, for whom Spleen (centre) is the mother]. Ginger and dates as envoy mobilise Spleen’s yin and yang-fluids and harmonise the nutritive and protective qi. [This makes up Gui Zhi Tang (Cinnamon Twig Decoction)].
If the bowels are open but there is still slight wheezing then Hou Po and Xing Ren are added, in order to facilitate Lung qi. [This makes up Gui Zhi Jia Hou Po Xing Zi Tang (Cinnamon Twig Decoction plus Magnolia Bark and Apricot Kernel)]. If after sweating the pulse is deep and slow, then Ren Shen (ginseng) is added, to augment Lung qi. [This makes Gui Zhi Xin Jia Tang (Cinnamon Twig Decoction with new additions)].
All of these are Lung and Spleen herbs. Thus although Gui Zhi Tang is a light formula for releasing the greater yang muscle layer, in fact they are herbs to regulate Spleen and rescue Lungs.
The above is secret tutelage not brought out through a thousand ages; I humbly disclose it, for clarity’s sake.