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The *Zhizhi* text states: The manifestations of Gu poisoning include a bluish-yellow complexion, fatigue and body pain, dry and cracked lips and mouth, loss of eyebrows and beard, irritability with dizziness and confusion, chest and abdominal fullness and stuffiness, abdominal distension with tight skin, severe abdominal pain as if bitten or crawled by insects, vomiting of fresh blood, dribbling urination, and bloody purulent stools. The food consumed by the patient transforms into insects that erode the Zang-Fu organs; severe damage leads to death. Upon death, toxic vapors circulate throughout the body and infect others, a condition known as "Gu Zhu" (Gu Transmission).

A pulse that is tight and rapid like a hairpin shaft, or wiry and straight accompanied by severe vomiting, indicates Gu poison. Urgent treatment is required. A surging and large pulse in Gu poisoning suggests survival; a faint and fine pulse indicates death.

When entering regions where Gu exists, food and drink can be tested with rhinoceros horn (*Rhinocerotis Cornu*). If toxic, white foam will rise vigorously; if no foam appears, it is non-toxic. Individuals who have eaten cat meat since childhood are immune to Gu poison.

For those poisoned by Gu, if one can recall which specific substance caused the poisoning, one must never consume that substance again for life; otherwise, the toxin will reactivate. If cured by medication, cold foods must be strictly avoided thereafter; consumption of cold food will cause the Gu poison to recur, ultimately becoming incurable.

The *Weisheng* text states: When entering Gu-infested areas, observe households where doorsteps and roof beams are completely free of dust and exceptionally clean; such families likely rear Gu, and one should take precautions. If one must eat their food, secretly hide a piece in hand when first placing chopsticks down; eating the rest is safe. Afterward, bury the hidden piece at a pedestrian crossroads. This causes the Gu spirit to disturb the owner's home instead, compelling the Gu master to beg for forgiveness. Alternatively, allow the host to start eating first, or directly ask, "Do you keep Gu?" Tap the table with chopsticks before eating. These methods prevent harm and have been verified in Gu regions.

Pain and distension in the chest and diaphragm indicate toxin in the Upper Jiao (Upper Burner); emesis is indicated. The method involves mixing 5 fen of Vitriolum (*Chalfan*, Alum) into half a cup of hot water, taking it orally, and after a short while, inducing vomiting with a goose feather quill until all toxins are expelled, leading to recovery. Alternatively, administering Shengma Decoction (*Shengma Tang*) to induce vomiting is also effective.

Abdominal pain and distension indicate toxin in the Lower Jiao (Lower Burner); purgation is indicated. The method involves taking 2 qian of Curcuma Aromatica Powder (*Yujin*, Turmeric Rhizome), mixed with rice soup, taken on an empty stomach to induce purgation, aiming to expel all malignant toxins. Following purgation, administer three doses of Sijunzi Decoction (*Sijunzi Tang*, Four Gentlemen Decoction) for regulation, observing strict dietary restrictions.