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The *Kaogong Ji* (Record of Examination of Craftsman Skills) states: "When oranges cross the Huai River to the north, they become trifoliate orange." This is because the orange receives the warm and hot qi of Jiangnan, thus its aroma and flavor are pungent and warm, capable of reaching the qi of the central earth (spleen and stomach), and irrigating the four extremities. The trifoliate orange (Zhi Shi) bears the cold and cool qi of Jiangbei; its nature and flavor are bitter and cold, capable of expelling pathogenic cold and heat downwards. It is one substance with different natures due to the qi of heaven and earth. The *Shennong Bencao Jing* (Divine Farmer's Materia Medica) records that it governs severe wind in the skin, causing itching like hemp seeds or bitter beans; it can initiate the emergence of cold water qi to counteract yang pathogens. (Trifoliate orange leaves do not fall in winter, indicating they have obtained the qi of cold water.) Oranges are harvested only after ripening, when heavenly qi is full, so their action spreads horizontally across the four limbs. Trifoliate orange fruits are immature and small; their qi is astringent, so they specifically descend and drain downwards. Regarding the bitter draining property of Zhi Qiao (Immature Bitter Orange Peel), its nature can also expand horizontally. Therefore, the *Bencao Jing* mentions only the fruit (Shi) and not the peel (Qiao). It was not until the Song Dynasty that a distinction between Qiao and Shi was made. If the disease involves solid accumulation in the chest and abdomen requiring purgation, one should use Shi (the fruit); using Qiao as a substitute indicates superficial understanding and lack of efficacy.

Ju Pi (Tangerine Peel) has an aromatic odor, yellow color, sweet taste with a hint of pungency. Sweetness, aroma, and yellow color belong to Earth; pungency belongs to Metal. Stomach Earth governs the collaterals (the Stomach also belongs to the Yangming channel, and Autumn Metal is white); Spleen Earth governs muscles; Lung Metal governs the skin and hair. The white membrane inside Ju Pi resembles the collaterals governed by the Stomach; the white part inside the peel resembles muscle; the pores on the outer surface resemble the skin. This represents a pathway from the interior to the exterior, from channels to collaterals, from collaterals to muscles, and from muscles to skin. Ju Pi can disseminate sweat from the Yangming channel and resolve rebellious Stomach Qi causing hiccups, as it can promote the flow of Stomach Qi outward to the skin and hair. If pathogenic factors in the couli (skin and interstices) rebel inward causing wheezing and urgency, or phlegm above the diaphragm accumulates upward causing coughing, and one wishes to resolve phlegm and direct Qi downward, this follows the reverse path: from muscles to collaterals, from collaterals to channels, and from channels to the Stomach. Whether pathogenic or righteous Qi desires to exit or enter, using Ju Pi as a guide relies on the internal white membrane. If this white membrane is removed, the pathway for entry and exit is severed. Therefore, the *Bencao Jing* refers only to "Ju Pi" without distinguishing between retaining or removing the white pith.