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The disease has persisted for seven days. After two administrations of warm resolving methods, the chills and fever subsided but recurred, accompanied by dry retching, absence of thirst, greasy tongue coating, and headache. The etiology lies in the patient's inherent deficiency; due to greed for coolness amidst heat, the pathogen of Yin-Shu (Yin Summerheat) was contracted, and those with weak constitution easily fell ill. The prescription Liyin Decoction (Nourishing Yin Decoction) was formulated, hoping that through its action, the internal qi mechanism would transform like clouds steaming and rain condensing, allowing the pathogen to pivot from Shaoyang (Lesser Yang) and return to the pathway of malaria, which would be auspicious.

The chills and fever occur at regular intervals, accompanied by yawning and discoloration of the fingernails, suggesting a progression toward malaria. However, since the Yin-Shu pathogen lingers, this condition is not comparable to typical malaria presenting at onset. It is still appropriate to employ methods to strengthen the middle jiao and warm/support the interior, combined with Ginger and Jujube to harmonize. Currently, chills are present; let us observe the severity of the fever tonight and discuss further tomorrow.

The chills and fever persist, indicating the pathogen remains unresolved. The mouth is still not thirsty, and the body still fears wind. Although it is midsummer, four doses of Ginger and Aconite have been administered without signs of fire/heat excess. If this were not Yin-Shu, how could such warming medicines be tolerated? Regardless of whether it is malaria or not, it fundamentally belongs to deficiency of righteous qi and lingering pathogen. Assisting righteous qi is tantamount to dispelling the pathogen; strengthening the host is tantamount to driving out the bandit. Yesterday, fever lasted until the fifth watch (5-7 AM), subsiding only after sweating. Today, it resumed at noon (11 AM-1 PM), accompanied by vomiting, nausea, and yawning. Previously, there was slight aversion to cold; this time, there was no sense of cold. The pulse is wiry and rapid, indicating a shift from Yin to Yang. Generally, when a Yin syndrome transforms into a Yang syndrome, it is favorable. Since the syndrome has transformed to Yang, warm medicines should be withdrawn. One should stop upon hitting the target; excessive caution may damage Yin. The disease has lasted many days, depleting righteous qi; assisting righteous qi to drive out the pathogen is correct.

After sweating and fever reduction, the headache decreased slightly, but the pulse remains wiry and rapid. The tongue coating has turned yellow, and pruritic papules (skin eruptions) are fully visible; it is undeniable that the Cold pathogen has transformed into Heat. Fearing that excessive Heat will damage Yin, Bu Yin Yi Qi Decoction (Supplementing Yin and Boosting Qi Decoction) is selected for modification. With constitutional deficiency and external contraction lasting twelve days, now there is only fever without chills. Onset occurs at noon, and cooling follows dawn sweating. This is indeed caused by latent Summerheat. Compared to Shanghan (Cold Damage), the presentation is slightly milder; compared to typical malaria, the chills and fever are indistinct. The Classic states: "Shaoyang serves as the pivot." If the latent Yin-Shu pathogen can pivot through Shaoyang, it is a good sign; otherwise, pathogen and righteous qi will mix chaotically, like lead and copper mixed into silver, losing its true nature. Shanghan can be resolved with one sweat; Warm-Shu requires multiple sweats to eliminate. This is because Damp-Heat pathogens hide in the Membrane Source (Moyuan), making them difficult to expel. Now that the Cold pathogen has transformed into Heat, it seems clear heat-clearing methods could be used. However, the origin of the illness ultimately stems from the Yin aspect. Having just transformed to Yang, bitter-cold medicines should not be introduced abruptly. Yesterday, using nourishing Yin and harmonizing methods, night fever lightened slightly, headache decreased slightly, and rapid pulse flattened slightly. Viewing the overall situation, maintaining this approach for two periods (approx. 4 days) should yield results.

Fever onset is slightly later, and the momentum feels peaceful. Cooling occurs at dawn, but thirst and fluid intake are increased. Sweating continues until noon without stabilizing. Summerheat sweat differs from deficiency sweat. The Classic says: "Summerheat should be released with sweat; do not stop it prematurely." The rapid pulse gradually slows, headache lightens, urine becomes lighter, and little pathogen remains. Approaching the end of the second period, recovery is near. Pure fever without chills is termed Dan Malaria (Crimson Fever Malaria); "Dan" refers to hyperactive Yang, so medication strategy must change. Yesterday, fever fluctuated, pulse rapidness normalized, and spirit improved slightly. However, yellow coating remains at the tongue root, and thirst persists, indicating residual latent Summerheat. For the next two days, fever will not cease abruptly, but since attacks are timed, it aligns with Dan Malaria. The Inner Canon attributes this to isolation of Yin qi and solitary emission of Yang qi. Add Jianyi Yiyin Decoction (Modified One-Yin Decoction). Yesterday's fever occurred again but with lesser intensity. The syndrome is Dan Malaria due to latent Summerheat, leaving no ambiguity. Yu Jiayan discussed Dan Malaria, grasping the subtle principles of the *Inner Canon* and *Jin Gui Yao Lue*, inspired by "adjust diet and regulate with sweet medicines," advocating sweet-cold herbs to preserve Yin and fluids. *Zhinan Yi An* treats this with pear and sugarcane juice, sharing this intent. Analyzing the symptoms, they resemble late-onset autumn conditions, differing only slightly in climate context but largely similar in presentation. Only after two or three periods, with daily reduction, can full resolution be achieved, promising a complete cure at that time.

An Bo notes: Regarding autumn latent qi diseases, only *Jiren Bian* offers unique insights with clear discussions. To date, Ye Tianshi alone has mastered these subtleties; few others have achieved this.