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This is the human cranial vault. Since the brain is the convergence point of all Yang meridians, and this bone serves as the master of all bones in the body, its taste is salty, nature is neutral, and it is non-toxic. It utilizes the principle of "similar things attracting each other" to treat *Chuan Shi* (a chronic wasting disease caused by "tubercle worms") and *Shi Zhu* (an infectious form of tuberculosis), and is needed for dispelling evil and scattering pathogenic factors. However, the *Du Ling Ying Xian Shu · Yao Xing* states: Even if borrowed for the opportunity to heal a life-threatening condition, one must first ask about the sin of being crushed into pieces. Although the medicinal properties remain, benevolent gentlemen should absolutely not use this substance, lest they harm the Heaven and Earth's virtue of fostering life, and would there not be the tragedy of cannibalism? Tianlinggai (Cranial Vault), even if miraculous powers are established, the karmic retribution in the Yin realm is profound; I dare not lightly elaborate to avoid heavenly punishment. Beware.

It refers to the crotch area of women's trousers. Cut the part corresponding to the external genitalia, burn it to ash, and take it orally. Because it resides in the lower body, it possesses abundant Yin Qi. Following the principle of resonance between similar entities, its Qi interacts to guide out pathogenic heat. Therefore, it primarily treats *Yin Yang Yi* (a condition where Yin and Yang energies become disordered and intermingled due to sexual intercourse shortly after severe illness). If the crotch of an virgin girl is used, the effect is even better. The so-called *Yin Yang Yi* occurs when a person suffering from an acute illness engages in sexual intercourse later, causing Yin and Yang energies to immediately adhere to each other, becoming more severe than the original illness. Symptoms include red and scanty urination with dysuria, severe alternating chills and fever, headache, lumbar pain, tinnitus, and blurred vision. After taking this medicine, free flow is restored; if the glans penis swells slightly, it indicates recovery. If a woman suffers from *Yang Yi*, she needs a man's crotch; if a man suffers from *Yin Yi*, he needs a woman's crotch. To treat diseases obtained through the exchange of Yin and Yang, use substances of Yin and Yang.

Menstrual cloth. Menstruation is called *Tian Gui* (Heavenly Water), which is water generated by Heavenly One. It corresponds to the Tai Yin (Moon) above and sea tides below. The moon has waxing and waning phases, and tides have morning and evening rhythms; thus, menstruation occurs once a month, matching these cycles. Its taste is salty. Salty flavor transforms via Water; heat toxins are resolved by Water. Therefore, it can resolve extremely toxic arrow poisons. *Nü Lao Fu* (female relapse due to labor/sexual activity) occurs after a febrile disease has just healed, triggered by sexual contact. Symptoms include fever, irritability, pulling pain in the lower abdomen and scrotum, or testicles retracting into the abdomen, and abdominal pain nearly causing death. This is because residual heat from the previous illness has not been eliminated, and Yin essence is damaged again, leading to these symptoms. Menstrual blood is a substance containing Yang within Yin; it can tonify Yin and clear heat, hence it is used to treat this condition. For *Jin Chuang* (metal weapon wounds) with unceasing bleeding, as well as wounds from tiger, wild boar, or wolf bites, and male genital ulcers caused by ignoring prohibitions against sexual intercourse during menstruation leading to genital rotting: use blood from a virgin, burn it on a tile until the property remains (*Cun Xing*), grind into powder, and apply mixed with sesame oil. These are all diseases caused by injury to the Blood aspect, treated by supplementing deficiency through the principle of similarity.

The first menstruation of a virgin girl is called *Hong Qian* (Red Lead). It can restore Yang Qi on the verge of collapse. Calculating from the time of conception, by age fourteen, a total of 5,400 periods accumulate. On that specific day and time, when menstruation arrives, this is considered the "Correct Cauldron," and its menstrual blood is the supreme medicine. The method involves attracting Qi; if True Qi arrives before the menstrual blood, collecting it into the body is named obtaining the "Great Medicine," which can extend life. This is what is recorded in the *Shou Leng Yan Jing* as "Essence Immortal." It is absolutely not alchemical interaction in a furnace, nor communication through emotional visualization, nor oral ingestion of dregs; thus, it can also achieve the Dao of Immortality. Xiao Zizhen said: There are those of heterodox schools who love lust, forcing Yang only to collect others' Yin, holding Tian Gui in their mouths calling it medicine. Such wet and filthy practices are futile efforts. This statement refers to the Great Dao of Golden Elixir, which relies only on emptiness and stillness to collect the Pre-Heaven Ancestral Qi. Moreover, without forming the elixir, how can the Four Elements (Earth, Water, Fire, Wind) be sought? Can one seek it in dregs? Those who suffer from extreme heat after taking Hong Qian can only be relieved by child urine and breast milk.

Kuchangzhi (Crotch Juice/Solution): Obtained from virgin boys and girls, the efficacy is stronger. It effectively treats *Yin Yang Yi*. Burn to ash retaining the property, grind into powder, and swallow with decoction. Female patients need male crotch, male patients need female crotch. Menstrual cloth burned to ash resolves drug and arrow poison like magic; if poisoned to near death, taking it brings immediate revival. It is also effective for treating *Nü Lao Fu*. Hong Qian is a point of true Yang in the Kan Palace, falling unintentionally into the mortal world. It is true gold in water, with methods to collect it to extend life.