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Poria (Fuling), sweet and bland in flavor, neutral in nature, descending, yin within yang, non-toxic. There are two types: red and white, with the white being superior. It enters the five zang organs of the Heart, Spleen, Lung, Liver, and Kidney, and also connects to the Bladder, Large Intestine, Small Intestine, Danzhong (Pericardium), and Stomach meridians. It assists Yang, benefits orifices, unblocks bowels, does not dissipate essence and qi, its blood-invigorating action is limited to the waist and umbilicus, removes dampness and promotes water metabolism, nourishes the spirit and enhances intelligence, generates body fluids, warms the Spleen, eliminates phlegm-heat, benefits the Lung, harmonizes the Hun and refines the Po, opens the appetite and thickens the intestines, treats epilepsy and convulsions, calms the fetus, and long-term use promotes longevity and anti-aging.

Fushen (Poria with Hostwood) is a type of Poria. However, Fushen grows embracing the roots of pine trees, retaining the meaning of remembering one's roots; thus, it is particularly effective in tonifying Heart Qi, stopping dizziness and palpitations, and especially treating forgetfulness. Its other functions are identical to those of Poria. Both herbs possess the characteristic of promoting drainage while providing tonification, making them suitable for both short-term and long-term use. They can serve as Sovereign (Jun), Minister (Chen), Assistant (Zuo), or Envoy (Shi) herbs. Only their dosage weights need differentiation; there is no debate regarding their beneficial or harmful effects. Some say they should be avoided in cases of excessive sweating and Yin deficiency; what harm is there in using a small dose? Others say they should not be taken by those whose urination is normally clear and frequent, fearing they may aggravate dryness and damage Yin; what objection is there to using a slight dose? Acute illness differs from chronic illness, and strengthening the Spleen is precisely suitable for chronic conditions; why completely eliminate Poria? Danxi stated: "Poria has the ability to promote water metabolism; long-term use damages the person." In Ba Wei Wan (Eight-Ingredient Pill with Rehmannia), it is used merely to guide other herbs into the Kidney meridian, remove accumulated stagnation in the uterus, and serve a transport function. Ba Wei Wan contains Cinnamon Twig (Guizhi), Aconite Root (Fuzi), Prepared Rehmannia Root (Shudihuang), and Cornus Fruit (Shanzhuyu) which directly enter the Kidney; why rely on Poria for meridian guidance? Zhang Zhongjing's use of Poria in Ba Wei Wan holds profound significance. Since Prepared Rehmannia is purely Yin and its nature is overly cloying and stagnant, although Alisma Rhizome (Zexie) promotes water metabolism, the moistening effect of Prepared Rehmannia is sufficient to counteract it. However, Alisma is too draining and may not effectively strengthen the Spleen to resolve dampness. Therefore, Poria is also used to assist it; it benefits the waist and umbilicus without dispersing Qi, ensuring that Alisma does not drain excessively. Thus, draining contains tonification, assisting Prepared Rehmannia, Chinese Yam (Shanyao), and Cornus Fruit in rapidly generating Yin. It is certainly not used merely for guiding purposes.

One asks: Poria strengthens the Spleen, yet Zhang Zhongjing uses it to benefit the Kidney; does this imply simultaneous treatment of the Spleen and Kidney? Although Poria enters the Spleen, Zhang Zhongjing’s use of it is entirely not for strengthening the Spleen, but solely for benefiting the Kidney. The Kidney dislikes dryness but also dislikes dampness. Excessive dryness leads to fluid depletion and easy flare-up of Fire; excessive dampness causes pathogenic retention and difficulty in generating Essence. In Liu Wei Wan (Six-Ingredient Pill with Rehmannia), Poria is used to drain evil water from the Kidney to tonify true water within the Kidney. Therefore, it has nothing to do with strengthening the Spleen; do not mistake it for simultaneous Spleen-Kidney treatment.

One asks: If Poria does not strengthen the Spleen but benefits the Kidney, yet Poria is indeed a substance that strengthens the Spleen, does this mean that when the Kidney is healthy, the Spleen is also healthy? That the Kidney is healthy and the Spleen is also healthy is the function of Liu Wei Wan. Poria can only benefit the Kidney to open the Stomach. The Stomach is the gatekeeper of the Kidney; when Kidney Qi is sufficient, the gatekeeper is vigorous. This cannot be attributed solely to Poria. However, the Qi of Poria indeed first communicates with the Stomach. Poria is a downward-draining herb; how can it ascend to the Stomach? One must understand that Poria particularly opens the orifices of the upper and lower parts. The Stomach is also the sea of water and grain. If water is drained but does not enter the sea, where will it flow? Thus, it drains downward to the Bladder and opens upward to the Stomach. When Stomach Qi receives the ascending vapor of Kidney Qi, will Stomach Qi not open further, and will food intake not increase? It seems that a healthy Spleen allows containment, but actually, it is a healthy Stomach that allows reception.

One doubts: Poria and Alisma are both water-draining substances. Some say Alisma is too draining, others say Poria fails to strengthen the Spleen. These views contradict each other. Do you claim novelty, Master? I reply: It is not about novelty. These two herbs truly have distinct functions and must be discussed separately. Alisma: within draining lies tonification; highlighting its tonifying merit shows its draining action is useful. Poria: within tonification lies draining; discussing the benefit of its draining shows its tonifying action is also useful. All herbs have merits and faults. Clearly distinguishing merits and faults in one’s mind ensures no errors in clinical practice.

One asks: The principles in Liu Wei Wan have been fully expounded. Are there other theories regarding Poria beyond the previous discussion? The previous discussion is insufficient to exhaust the meaning of Poria. When Zhang Zhongjing used Poria in Liu Wei Wan, did he merely drain evil water from the Kidney to tonify true water? Poria can further enter the Kidney to communicate the Fire Qi within the Kidney. Kidney Fire Qi communicates upward to the Stomach and downward to the Bladder meridians. Without the communication of Kidney Fire Qi, upper water cannot enter, and lower water cannot exit. Upper water not entering does not mean inability to drink, but rather that the Qi of ingested water fails to transform. Lower water not exiting does not mean inability to hold, but rather that the Qi of water fails to excrete and transform, causing water to surge in the Middle Jiao and fail to metabolize. Only with Fire Qi communication can upper and lower waters circulate freely without stagnation. Liu Wei Wan tonifies Kidney Water but does not tonify Kidney Fire; thus, Fire cannot spontaneously communicate with the Stomach and Bladder. With Poria acting as an agent for dissemination and transformation, upper and lower waters can move. Why worry about failure to transform or excrete? The use of Poria in Liu Wei Wan holds such subtle meanings.

Another question: Poria has such奇 (extraordinary) meanings in Liu Wei Wan; does its use in Ba Wei Wan also carry different significance? I reply: Yes. Poria drains water and can also drain Fire. Draining water refers to draining evil water from the Kidney; does draining Fire not refer to draining evil Fire from the Kidney? Ba Wei Wan uses Cinnamon Twig and Aconite to tonify Fire, specifically tonifying true Fire in the Kidney. However, if true Fire in the Kidney is tonified while evil Fire remains, true Fire will not generate; instead, it will exacerbate evil Fire and cause it to ascend. Zhang Zhongjing’s use of Poria in Ba Wei Wan precisely aims to drain evil Fire to support true Fire. With the assistance of Poria, Cinnamon Twig and Aconite are free from interference by evil Fire, allowing true Fire to grow rapidly. Consequently, Fire generation benefits Spleen Earth, enabling it to receive water and grain; Stomach Earth benefits, allowing dietary intake without obstruction; Lung Qi regulates, Heart Qi descends, and Liver Qi levels out.

Another question: Poria’s use in Si Jun Zi Tang (Four Gentlemen Decoction) and Liu Jun Zi Tang (Six Gentlemen Decoction) seems not primarily for water drainage. Why not speak of its extraordinariness here? When Poria is used within Yin-tonifying formulas, it can produce extraordinary effects. When used among Yang-tonifying herbs, its uniqueness is less apparent; it merely assists Ginseng Radix (Renshen) and Atractylodes Rhizome (Baizhu) to distribute and eliminate dampness, thereby consolidating Spleen Earth and opening Stomach Qi.

Another question: Poria’s use in Du Qi Wan (Duqi Pill) does not seem extraordinary either. It requires Cinnamon Bark (Rougui) to drain water. How can it be considered extraordinary when entering Shen Qi Wan (Kidney Qi Pill)? I reply: The wonder of Shen Qi Wan lies entirely in Poria. Everyone knows Poria promotes water metabolism. Within water drainage, aided by a group of Yin herbs, it can better exercise its authority to drain water during water tonification; aided by two Yang herbs, it can better complete its divine power to transform water during Fire tonification. It drains only evil water without causing turbulent overflow, and does not damage true water but instead transforms heat to steam, communicating the Upper, Middle, and Lower Jiao, and eliminating internal and external dampness. All these are the merits of Poria as the Sovereign herb. If Poria were made a Minister herb and Prepared Rehmannia the Sovereign, stagnation in the Middle Jiao would inevitably occur, water would accumulate in the skin and fail to enter the Bladder directly, and how could it be drained?

One asks: Xia Ziyi collected strange prescriptions for curing diseases. There was a case where a person’s ten finger joints were broken and damaged, connected only by tendons without joint flesh, worms emerged like rush pith, several inches long, covered in green hair all over the body. He was cured by decocting and drinking Poria and Picrorhiza Rhizome (Huhuanglian). Does this also have meaning? I reply: This is worms caused by Damp-Heat. Poria removes dampness, Huanglian (Coptis Rhizome) clears heat. When Damp-Heat scatters, the worms die naturally. However, the green hair on the worm bodies holds a secret meaning. This person likely played with frogs in a pond. A turtle with green hair in the pond tried to swallow the frog but failed. Thus, Qi rushed to the hand, causing rotting over time. The extreme Yin toxin entered but did not disperse, causing skin decay and flesh corruption, leading to the growth of worms with green hair. Unfortunately, I raised this dissenting view, but no one verified it.

One asks: Nowadays, people often soak Poria in human milk. Long processing turns the white color red. Is this beneficial to humans? When using Poria in tonifying medicines, it is feared that pure tonification may cause organ stagnation; thus, Poria is used to ensure smooth circulation, aiding tonification through draining. If processed excessively with milk, its draining and unblocking nature is completely lost. It becomes a rigid tonification, failing to assist tonifying medicines to achieve success. This reflects modern ignorance of the efficacy of herbs and reckless alteration of processing methods, which should not be followed as a standard.