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The taste is sweet, the nature is neutral, and it is non-toxic. It primarily treats wind-pathogenic bi-syndrome (obstruction syndrome caused by wind) and facilitates the nourishment of bone marrow. It can be used for making external massage medicines. Its nature is cold and purgative, and its efficacy surpasses that of Su (Clarified Butter). It is produced within Su.

The commentary in *Tang Bencao* states: This is the essence fluid of Su. From one dan (a unit of volume) of high-quality Su, three to four sheng (a unit of volume) of Tihu can be obtained. After being cooked, beaten, and refined, it is stored in a vessel to await coagulation. By piercing through the center to the bottom, the liquid flows out and can be collected. Tao Hongjing claimed it could be made into yellow-white cakes; this statement shows a lack of understanding. (This note was originally attached earlier.) Ministers Yu Xi et al. respectfully examined the Shu edition, which states: Another theory says that what exists within Su, does not congeal in deep winter and does not melt in midsummer, is indeed Tihu. Ri Hua Zi stated: Tihu stops palpitations and fright, treats heart-heat and headache, brightens the eyes, and when applied to the vertex of the head...

The *Tujing* has detailed entries under the section for Niuhuang (Calculus Bovis).

Chen Zangqi noted its slippery nature; it permeates through any container holding it; only chicken eggshells and gourd ladles prevent leakage. Lei Gong said: It is the whey of Lao (fermented milk). For medicinal use, it must be filtered repeatedly through thick cotton cloth, boiled two or three times in a copper vessel, and then used. The *Shiliao* records its nature as neutral. It treats wind-pathogens and nourishes bone marrow. Its nature is cold and purgative, being the essential essence of Su.

The *Taiping Shenghui Fang*: Treats stroke with vexation and heat, and skin itching. Use four liang of Tihu, mixed with wine for half a spoonful per dose. The *Shiyi Xinjing* treats all lung diseases, coughing, and continuous discharge of pus and blood. Take five jin of high-quality Su, melt it three times, let it stand until it coagulates; the substance that rises to form Tihu should be taken. One he (a unit of volume) cures the condition. Another prescription: Treats deficiency and removes wind-dampness bi-syndrome. Take two large liang of Tihu, mix with one cup of warm wine, and take together with one spoonful of Tihu.

The *Yanyi* states: When making Lao, the top layer that coagulates is called Laomian (curd surface); the layer above the Laomian that looks like oil is Tihu. It is extracted by heating, but yields are low. It is extremely sweet and delicious. Although obtained this way, its applications are few. It is most suitable for moistening and nourishing scabs.

It stops thirst.

Tao Yingju stated: People nowadays do not consume it much, likely because it is hard to obtain. The *Tang Bencao* commentary notes: Horse milk and donkey milk share the same cold and purgative nature; they stop thirst and treat heat. Making Lao from horse milk makes it even colder. In Jiangnan, horse milk is scarce; currently, it is generally considered cold, which is accurate. Donkey milk treats mild yellow fever, childhood internal heat, and convulsive heat; taking it also provides a purgative effect. Hu people claim that horse Lao is warm in nature and helps digest meat. Generally, things control each other based on their categories, without strict adherence to cold or hot natures. Ministers Yu Xi et al. respectfully examined the Shu edition, stating: Horse milk, taste is sweet. The *Xiaoke Tongyong Yao* records: Horse milk, nature is cold. The *Yaoxing Lun* records: Horse milk, non-toxic.

Chen Zangqi recorded its sweet taste, ability to treat heat, and cold, purgative nature. Sun Simiao warned that eating it with raw fish causes Jia masses (abdominal lumps). The *Shiyi Xinjing* records that drinking horse milk stops thirst.