Founder’s Note : This is the third of a series of articles we’ll be releasing here about the theory and herbs of the Tang ye jing. The enthusiasm and scholarly integrity of the author – regular contributor Joshua Park, DSOM, LAc – will make this a thought provoking and engaging read that we hope you’ll share with friends and colleagues. Joshua is eager to hear your feedback, either here on the site or on our Facebook page.
All sour belongs to metal, for it is governed by Wuweizi, and Zhishi is wood,Chi is fire, Shaoyao is earth, and Shuyu [better known to modern practitioners as Shan Yao] is water.
Having explored Zhishi as the Wood of Metal, we now move on to the next phase in the cycle and come to Dandouchi (淡豆豉), the Fire of Metal.
Dandouchi is the fermented black soybean (Latin Name: Semen Sojae Preparata). Dandouchi is not the most commonly prescribed herb in classical herbalism (although it does feature prominently in several of Zhang Zhongjing’s formulas, which we will explore shortly). In fact, it is not even included in the Shen Nong Ben Cao Jing.
The first mention of Dandouchi in a Chinese materia medica is the Ming Yi Bie Lu (名醫別錄), an herbal text attributed to the Daoist alchemist Tao Hongjing. Recall that Tao is also the purported author of the Fu Xing Jue Wu Zang Yong Yao Fa Yao (輔行訣臟腑用藥法要), the previously lost manuscript that contains the only passages we have of the Tang Ye Jing.
Here is what the Ming Yi Bie Lu has to say about Dandouchi:
[Dan Dou] Chi: Its flavor is bitter, cold and nontoxic. It governs cold damage, headache, [alternating] cold and heat, malarial qi, evil toxins, vexation agitation, stifling fullness, taxation fatigue, panting on inhalation [and] cold pain of both feet; moreover, it kills all various toxins in the six domestic animals, fetuses and children.
We can see from this that Tao’s understanding of Dandouchi makes it a tremendously useful herb.
However, just as we did with Zhishi, there is a seeming discrepancy here: the Tang Ye Jing classes Dandouchi with Metal, and therefore Sour, and yet the Ming Yi Bie Lu describes it as being bitter and cold. Modern materia medicas such as Bensky tend to agree with this classification, but also emphasize its acrid nature. And of course the Tang Ye Jing associates Fire with Salty, and none of the Materia Medica state that Dandouchi is salty. So how are we to understand this in terms of the Tang Ye Jing’s classification?
Fire of Metal
Let’s consider what it means for Dandouchi to be considered the Fire of Metal. We saw in our exploration of Zhishi as the Wood of Metal that Zhishi’s activity could be seen as carrying the action of Metal into the domain of Wood (specifically, through its activity of strongly descending the Gallbladder and breaking knotted qi).
In a similar fashion, then, we must understand Dandouchi’s action as involving the relationship between Metal and Fire. And we know that this involves the Controlling Cycle, as Fire Controls Metal.
Examining Zhang Zhongjing’s formulas with Dandouchi will help make this more concrete. Most of formulas that contain Dandouchi can be found in Clause 76 of the Shang Han Lun:
After sweating is promoted, if water and medicine are unable to be ingested due to counterflow [but] again sweating is promoted, there will be incessant vomiting and diarrhea. After the promotion of sweating and the use of vomiting or purging [methods], there is empty vexation with inability to sleep; if the condition is severe, with tossing and turning and anguish in the heart, Zhizi Chi Tang governs it. If there is shortage of qi, Zhizi Gancao Chi Tang governs it. If there is nausea, Zhizi Shenjiang Chi Tang governs it.
There’s quite a bit to unpack in this clause, and extensive debate in the commentaries over what is meant precisely by many of the terms in this line, such as ’empty vexation’ (xu fan虛煩). The general consensus though is that describes a presentation of formless (1) stagnant heat in the chest. Improper usage of purgatives, vomiting, or excessive sweating pushes the pathogenic factor further into the body where it becomes trapped in the upper burner. The vexation and anguish described the line are all signs of heat.
Although the line mentions the Heart specifically, we can understand this as involving the chest cavity more generally.
Insofar as the chest cavity houses the Lungs, and is also implicated in Yangming disease we can say that it belongs to Metal. Nausea, vomiting, and shortage of qi (which in this context may simply mean shortage of breath) are also pathologies that all belong to the Metal organs of the Lung and Stomach. The same pathology described by Line 76 can also arise in Yangming disease; see Lines 221 and 228, which also describe a situation of formless heat in the chest, and for which Zhizi Chi Tang is also indicated.
To summarize then, the clinical situation described here then is one of heat (Fire) trapped in the chest (which belongs to Metal) – and a key herb to treat this pathology is Dandouchi, which opens and vents the Lung, allowing the heat an exit. Its cold nature helps to soothe vexation, and also resonate with the cool qi of Autumn that likewise belongs to Metal. Based on this analysis, we can say that the main action of Dandouchi is to protect Metal from being damaged by Fire by venting heat from the chest. It is classified as the Fire of Metal, because it functions to removes Fire from Metal.
Post Classical Formulas
Dandouchi features prominently in a number of post-classical formulas where it performs the same function as it does in Zhizi Chi Tang and its modifications. The most famous of these is the formula Yin Qiao San (銀翹散), which is indicated in the Wen Bing Tiao Bian (温病條辨) for Taiyin Wind Warmth (太陰風溫), a pattern that manifests with signs of heat damaging Metal, such as sore throat. It is also frequently added to the pediatric formula Xie Bai San (瀉白散), devised by the Song Dynasty physician Qian Yi to drain stagnant heat from the Lungs.
Although it is beyond the scope of this article series to delve deeply into these post-classical formulas, it is worth mentioning because their usage of Dandouchi follows the same principles as Zhang Zhongjing’s usage, which is ultimately derived from the Tang Ye Jing. This demonstrates the deep and wide ranging influence that this text has over all of Chinese Herbalism.
I will move on to consider the next herb, Shaoyao, in the sequence in the next article. It’ll be an action-packed exploration since Shaoyao is such a frequently used herb!