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[Innovation]
The disease of Hongxiangjiao (Hong Kong foot / Gouty arthritis) is essentially caused by water-dampness. Dampness harms the human body, damaging the skin, flesh, sinews, and vessels, and its pathology predominantly resides in the lower part. However, there are two origins: one is contracted from the exterior, and the other arises from the interior. Therefore, their treatment methods should differ; thus, a detailed analysis follows.

This condition presents with symptoms but lacks a specific disease name. The term "Hongxiangjiao" originated with Su Jing during the Jin Dynasty. It was absent in the Guanzhong and Heshuo regions (the North). It only exists in the South, where underground water is cold. The clear-cold damp qi invades the human body, necessarily starting from the feet. Hence, the *Classic* states: "When clear-cold dampness attacks deficiency, illness arises from below." Some may object: "Currently, in the Northern regions, although the terrain is high and cold, and people's couli (pores/skin texture) are dense, many still suffer from this disease. Is it not due to local dampness acting as an evil pathogen?" The answer is: Southern diseases are contracted from the exterior; Northern diseases arise from the interior. (Detailed discussions on the North and South are found in previous sections.)

Exterior invasion results in swelling and pain limited to the lower legs. Interior origin may extend to the hand joints. The *Classic* states: "Swelling of the feet and shins is termed Water disease; swelling occurring at the Taiyin [Spleen] stage." This refers only to the exterior contraction. Predecessors have provided ample formulas and theories for treatment, but methods for interior-origin cases remain undefined.

Upon review, the previous discussion on the causes of Hongxiangjiao in both North and South is quite comprehensive. The present "Innovation" further emphasizes that this syndrome is primarily formed by water-dampness, synthesizing the主旨 (main themes) of the preceding two discussions. Although ancient texts lacked methods for interior-origin cases, observing several formulas proposed by Li Dongyuan reveals that their principles and examples are already well-established.

[Innovation]
The *Neijing* describes southern regions as having low terrain, weak earth and water qualities, and being gathering places for fog and dew. The Jiangdong and Lingnan areas are largely similar. During the transition between spring and summer, heat and moisture vaporize in mountains and rivers, making wind-damp toxic qi prevalent. If the feet are affected, miasma-toxic Hongxiangjiao forms. Its manifestations include initial weakness and flexion difficulty of the feet, progressing to numbness and pain, slight swelling of the shins, insensitivity of the lower abdomen, headache, vexation, phlegm obstruction with counterflow, alternating chills and fever in the chest, and obstruction of urination and defecation. In severe cases, the toxin attacks the heart, creating an urgent situation requiring immediate treatment. Zhifacun paid attention to classical formulas and excelled in treating this technique, likely because such diseases were more common in Jiangdong and Lingnan regions.

Upon review: Southern climates are warm and humid with frequent rain. Earth dampness, steamed by heat, permeates the skin and couli. Those with loose couli and deficient constitutions are prone to infection. Additionally, long-distance travelers whose feet become hot may be injured by cold water when crossing streams. The resulting transformations vary, let alone miasma-toxin cases. Recent cases in Jiangdong are mostly dominated by water-dampness, sometimes complicated by wind or cold. At onset, there may be swelling or pain. When damp-heat prevails, blistering sores form, or red swelling resembling erysipelas occurs. Alternatively, it may act like hernia qi attacking upwards and downwards. All these require detailed differentiation and separate treatments.