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The *Huangdi Neijing* (Yellow Emperor's Inner Canon) states: "If one is injured by cold in winter, one will inevitably suffer from warm diseases in spring." It also states: "If one fails to store essence in winter, one will inevitably suffer from warm diseases in spring." Analyzed separately, the former refers to the excess of pathogenic factors, while the latter refers to the deficiency of healthy qi.

Synthesized together, it implies that because one failed to store essence in winter, causing the kidney qi to be deficient first, the cold pathogen was able to invade. Although the rhetorical tone seems to place both on equal footing, their underlying meaning is consistent. Yu Jia Yan (Yu Chang) established three separate guidelines for "injured by cold in winter," "failing to store essence in winter," and "failing to store essence and additionally being injured by cold," each with its own syndrome differentiation and treatment. Consider this: if one merely failed to store essence in winter without suffering any cold injury, the resulting illness would be purely a deficiency syndrome, having no relation to warm diseases. It seems Yu Chang only cared about the rhetorical structure of his writing and did not realize that his statements were inconsistent with clinical reality.

Tracing back to the initial invasion of the pathogen, it is because the kidney qi was deficient first, allowing the pathogen to gather and lie dormant in the Shaoyin (Lesser Yin) channel. When spring arrives and yang qi moves internally, the latent cold pathogen transforms into heat and emerges. The onset can occur due to internal movement of yang qi, or it can be triggered by an external seasonal pathogen. In cases where internal yang qi moves and latent cold transforms into heat, although there may be slight chills externally, the interior heat is intense, with no aversion to wind or cold, painful joints, thirst, and scanty sweating (sweating is scanty at the beginning but becomes profuse when reaching the Yangming stage). Medication should assist yin qi to push the pathogen outward, preventing it from lingering. If the disease is triggered by a seasonal pathogen, one must identify what other pathogen is involved, such as Wind-Warmth, sudden Cold, or Summer-Heat. One should incorporate the intention of dispersing and resolving the new pathogen into the previous methods (see details under the section on external new pathogens). Observe the severity of the combined pathogen. If mild, it can be treated concurrently. If severe, priority must be given at the onset to resolving the new pathogen; only after the new pathogen is resolved should the latent pathogen be treated, so as not to interfere with each other. This requires weighing the severity and urgency to determine the treatment method, avoiding preconceived notions.

Cold pathogen lying dormant in Shaoyin inevitably damages yang; since kidney yang is weak, it cannot steam and transform to drive the pathogen out. It is often seen that when warm pathogen initially erupts, kidney yang is already depleted, causing the pathogen to become frozen like ice, unable to emerge. Amidst this struggle, the pathogen may sink inward, becoming incurable. This is the most difficult critical condition to treat (see details under the section on pathogen stagnation in Shaoyin). If the pathogen has already transformed into heat, the pathogenic heat spreads like a prairie fire, easily scorching and damaging yin fluids. Once yin fluids are damaged, complications arise rapidly. Therefore, in treating latent warm diseases, one must constantly protect the yin fluids. At the onset, the route for the pathogen to exit may be through the Three Yang channels or via the Lung and Stomach, with no fixed pathway, as the pathogen remains within the Shaoyin domain. Previous methods for treating warm diseases include: Sun Simiao's use of Yangdan Tang (Yang Decoction), which leans towards the Taiyang (Greater Yang) channel; Lu Jiuzhi's use of Gegen Qinlian Tang (Kudzu and Coptis Decoction), which leans towards the Yangming (Bright Yang) channel; Zhang Shiweng's use of Xiaochaihu Tang (Minor Bupleurum Decoction), which leans towards the Shaoyang (Lesser Yang) channel; Yu Jiayan's use of Mahuang Fuzi Xixin Tang (Ephedra, Aconite, and Asarum Decoction), which is overly aggressive; Ye Tianshi's use of acrid-cool clearing and resolving methods, which is superficial. I believe the most appropriate and unchangeable method is to use Huangqin Tang (Scutellaria Decoction) added with Dou Chi (Fermented Soybean) and Xuanshen (Scrophularia Root). Huangqin Tang is a specialized formula for clearing and draining interior heat. Dou Chi, made from black beans, enters the Kidney channel; it is also produced through steaming and fermenting, similar to the steaming and oppression mechanism of latent pathogens emerging; moreover, its nature and flavor are mild, without the drawback of forcing sweat and consuming yin. Thus, Dou Chi is the specific herb for venting latent pathogens in Shaoyin. Adding Xuanshen to tonify kidney yin allows for simultaneous clearing of heat and venting of pathogens. For all cases where warm pathogen initially erupts and the pathogenic heat has not yet left the Shaoyin channel, the treatment method does not exceed this principle. As for cases complicated by other external invasions, internal injuries, or where the pathogen has not yet left Shaoyin but presents with symptoms of the Three Yang channels, one must consult clinical signs and treat accordingly; this cannot be solved by rigidly applying fixed rules (like carving a mark on a boat to find a sword).