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The *Kanli Sha* (Caini Sand) sold in pharmacies generates heat spontaneously when vinegar is poured on it. Applying it with moxibustion-like warming to leg and arm pain caused by cold exposure is quite effective, yet many physicians are unaware of the underlying reason. Upon investigation, this phenomenon essentially boils down to the principles of chemical combination. This sand is composed entirely of iron filings. Its preparation method involves heating the iron filings until red-hot, then extinguishing them by spraying vinegar, followed by drying and storage. When used again, mixing with vinegar causes it to generate heat. This is because fire requires oxygen (*Yangqi*, 养气) to burn; when the iron filings are red-hot, they contain oxygen within them. After being extinguished by vinegar, this oxygen remains permanently bound within the iron. Furthermore, oxygen is an acid element, and vinegar is extremely sour, containing abundant oxygen. Spraying vinegar onto red-hot iron transfers the oxygen from the vinegar into the iron as well. When vinegar is poured on it during use, the previously stored oxygen is activated and released, generating heat. Applying this to areas painful due to cold-bi syndrome not only expels congealed cold but also promotes blood circulation, as human blood vessels turn red upon receiving oxygen, thereby resolving blood stasis.

Red Jing (a type of plant, likely *Rhus chinensis* or similar tannin-rich shrub) is abundant in my hometown, particularly in Bozhuang north of the county, where thickets surround field paths everywhere. In the late spring of the Yisi year, many cattle died of plague. Butchers discarded the viscera and consumed only the meat, with no reports of poisoning. However, in Bozhuang, over two hundred people simultaneously fell ill after eating beef, prompting me to be summoned for rescue. By the time I arrived (approximately three kilometers away), three had already died. The symptoms of poisoning included fever, nausea, dizziness/confusion, and a tight, rapid pulse. Administration of *Huanglian* (Coptis Rhizome), *Gancao* (Licorice Root), *Jinyinhua* (Honeysuckle Flower), and *Tianhuafen* (Trichosanthes Root) proved immediately effective. Detailed inquiry revealed the cause: the beef was washed in a stream where many Jing branches were steeping, turning the water red. It was then dried on a rack made of Jing branches, and later cooked using Jing branches as firewood. Those who bought and ate this meat became ill; those who ate more suffered severe illness, while those who ate less had mild symptoms. Hearing this, I suddenly recalled the local proverb "Old cow reacts with Jing flowers," which has been passed down through generations. I surmised that ancestors in our region must have suffered from this poisoning, hence the saying persists. Although few have witnessed it personally, leading to its gradual obscurity, the exact mechanism behind this antagonism awaits study by experts in chemistry. I also recalled reading a novel describing a rural woman walking through *Jingjie* (Schizonepeta Herb) fields, mixing it with rice containing beef, resulting in poisoning for the eater. I suspect "Jingjie" might be a misnomer for "Red Jing." Otherwise, how could beef react with both Jing flowers and Jingjie? I hope learned physicians among you can clarify this matter and offer guidance without reservation.