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Jincha Shihu (Dendrobium nobile), with a sweet and slightly bitter taste, is of a slightly cold nature and non-toxic. It should not be confused with Zhuxu (Bamboo Dendrobium) or Muxu (Wood Dendrobium); using them yields no efficacy. Shihu can calm fright and stabilize the spirit, benefit essence and strengthen Yin, and particularly possesses the power to strengthen the feet and knees. It is excellent for treating Bi syndrome (obstruction syndrome characterized by pain, heaviness, or numbness), descending fire due to Yin deficiency, and holds great special merit. Physicians in the Wu region (Jiangsu and Zhejiang areas) nowadays favor its use, yet people throughout the world do not fully understand its functions. This is because Jincha Shihu grows in rock caves in Guangdong and Fujian. Rock caves are places of extreme Yin, while Guangdong and Fujian are regions of extreme Yang. Born from inheriting the Qi of both Yin and Yang, its cold nature is not excessively cold, and it can descend floating heat. The so-called deficient fire refers to Ministerial Fire (Xianghuo). Ministerial fire is suitable for tonification rather than purgation. The subtlety of Jincha Shihu lies in the fact that although it is a cold herb, it also has tonifying properties, and its action moves downward rather than upward. Ministerial fire tends to ascend easily but descend with difficulty; with Shihu, it descends and does not ascend. During summer, when one's legs feel weak, taking Shihu restores strength. Is this not clear evidence of its ability to descend and simultaneously tonify Extreme Yin? Therefore, using Huangbai (Phellodendron Bark) and Zhimu (Anemarrhena Rhizome) to purge Ministerial fire is far less appropriate than using Jincha Shihu. Huangbai and Zhimu purge without tonifying, whereas Jincha Shihu tonifies while purging.

One might ask: Since Jincha Shihu descends fire due to Yin deficiency, it is a substance that drains Yin. How can it then strengthen the power of the feet and knees? The profound meaning here has not been fully elucidated. I reply: The Kidney is subject only to tonification, never to purgation. Why does Jincha Shihu drain the Kidney yet conversely tonify it? Your doubt is understandable. Although I briefly mentioned this earlier, I shall now explain it thoroughly. Within the Kidney, there is a distinction between Water and Fire. Insufficiency of Water leads to excess Fire; excess Fire leads to insufficiency of Water. The inability of Water and Fire to remain in balance has long existed. Weakness in the feet and knees stems from an insufficiency of Kidney Water. When Water is insufficient, Fire feels excessive; when Fire is excessive, Water becomes even more insufficient, failing to control the Fire. If Fire cannot be controlled, it flares up and boils dry the marrow within the bones. Under such conditions, expecting strength in the feet and knees is impossible. Jincha Shihu is not originally a medicine for directly benefiting essence and strengthening Yin; rather, it is a medicine that descends the deficient fire of the Mingmen (Gate of Life) in the Kidney. By removing the excess Fire, it naturally supplements the insufficient Water. By draining the deficient fire in the Kidney, it naturally replenishes the true Water in the bones. Hence it is said to "strengthen Yin and benefit essence." This is why the feet and knees become strong. Then, since Huangbai and Zhimu are also medicines that drain Kidney Fire, why can they not strengthen the feet and knees? One must understand that for Kidney Fire, herbs of Great Cold nature purge without tonifying, whereas herbs of Slightly Cold nature tonify while purging. The subtlety of Jincha Shihu lies in its Slightly Cold nature, achieving tonification through purgation. [Commentary: Ministerial fire is deficient fire; deficient fire must be tonified to subside. The effect of Shihu in tonifying the Kidney does not compare to Shudi (Prepared Rehmannia Root). However,凭借其 light and empty nature, it penetrates into the Yin fire of the Mingmen, guiding the fire of the Mingmen back to the Kidney. No other herb can replace Shihu. Herbs of Great Cold nature have purgative effects but no tonifying effects; herbs of Slightly Cold nature have tonifying effects but no purgative effects. This insight was not previously developed.]

One might ask: You dislike the use of Huangbai and Zhimu for purging fire, so why do you praise Jincha Shihu? You do not realize that Jincha Shihu cannot be compared to Zhimu and Huangbai. Zhimu and Huangbai are of Great Cold nature, entering directly into Extreme Yin, causing cold to penetrate deep into the bone marrow. Jincha Shihu is merely Slightly Cold; although it enters Extreme Yin, it expels cold from outside the bone marrow. There is a distinct difference between them.

Some may suspect that Jincha Shihu expelling cold from the bone marrow is indeed a novel theory not previously expressed, but lacking evidence makes it hard to believe. I reply: Because Shihu is Slightly Cold, it naturally does not damage the bones. If the bones are not damaged, the heat within the bones naturally resolves. Once the heat in the bones resolves, it necessarily dissipates outward. This is logically inevitable and does not require empirical evidence to be believed.