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The *Huangdi Neijing* (Yellow Emperor's Inner Canon) states: When the metal qi of the year is excessive, cough and reverse flow (Ke Ni) occur; when metal qi is stagnant and erupts, cough and reverse flow also occur; disharmony between Shaoyin (Lesser Yin) and Jueyin (Terminal Yin) qi can also lead to cough and reverse flow.

Examining the mentions of "cough and reverse flow" in the *Huangdi Neijing*, they are limited to these instances. In other medical texts, only the *Shanghan Lun* (Treatise on Cold Damage) mentions that "if pulse is scattered in cough and reverse flow, it is fatal," and the *Jingui Yaolue* (Essential Prescriptions of the Golden Cabinet) contains various formulas for treating cough and reverse flow with upward rushing qi. These seem to refer primarily to diseases involving Lung Metal and Fire pathogens.

The *Lei Zheng Huo Ren Shu* (Book of Active People for Classifying Patterns) considers the syndrome of "cough and reverse flow" to be extremely malignant and unrecorded by Zhang Zhongjing. Sun Simiao (Sun Zhenren) stated: "Searching through all formula theories, there is no name for 'cough and reverse flow'; thus, I conclude that cough and reverse flow is synonymous with hiccups (Yue)." However, the *Lingshu* (Spiritual Pivot) states: Hiccups occur because food enters the stomach, and Stomach Qi ascends to the Lungs. Therefore, cold qi and the qi of newly ingested food enter the stomach together. The old and new qi confuse each other, righteous qi and pathogenic qi attack each other, the qi merges and reverses, and re-emerges from the stomach, hence it is called hiccups. The commentary notes: "Yue" refers to qi clashing or conflicting. "Wu" means opposing or confronting.

The *Baoming Ji* (Collection for Preserving Life) further interprets "cough and reverse flow" as belching (Yi). Belching refers to the failure of qi interaction in the chest. The Shaoyin channel reaches the chest and intersects with the Jueyin channel; water and fire transmit to each other, producing sound. The *Lingshu* states: Belching occurs because cold qi lodges in the stomach, and rebellious qi rises from below and re-emerges from the stomach, hence it is called belching. The commentary notes: Belching resembles smoke following flames. Since the Heart does not accept pathogenic qi directly, belching emanates from it.

I believe both explanations have their merits, but I am uncertain if they are correct. Given the difficulty in determining the truth, I strongly refute Zhu Shi’s (Zhu Gong’s) errors regarding this matter; his arguments are presented later.

The *Lei Zheng Huo Ren Shu* states: Cough and reverse flow is what Zhang Zhongjing referred to as hiccups (Yue), which arises from Stomach Cold. In cold damage, if the body is already deficient, attacking the heat will inevitably cause hiccups. It also states: After severe vomiting and purging in cold damage, leading to extreme deficiency, followed by profuse sweating, hiccups may result. This is because the middle jiao is cold. Treatment involves Ju Pi Gan Jiang Tang (Tangerine Peel and Dried Ginger Decoction), Qiang Huo Fu Zi San (Notopterygium and Aconite Powder), Ban Xia Sheng Jiang Tang (Pinellia and Fresh Ginger Decoction), or Tui Yin San (Retreating Yin Powder). If ineffective, moxibustion at the point below the nipple will cure it. However, there are also Yang syndrome cases where cough and reverse flow are accompanied by tidal fever and frequent hiccups, treated with Xiao Chai Hu Tang (Minor Bupleurum Decoction) or Ju Pi Zhu Ru Tang (Tangerine Peel and Bamboo Shaving Decoction). It further states: In cold damage, if hiccups are accompanied by abdominal fullness, observe the anterior and posterior orifices; whichever is obstructed, unblock it to achieve recovery.

Analysis: Since the *Lei Zheng Huo Ren Shu* equates cough and reverse flow with hiccups, I now follow its classification, incorporating Zhang Zhongjing’s discussion of hiccups under the category of cough and reverse flow. Even if Zhang Zhongjing’s “hiccups” do not exactly match this syndrome, the patterns and medications discussed in the *Lei Zheng Huo Ren Shu* indeed target cough and reverse flow rather than vomiting or simple hiccups. Generally, cough and reverse flow often arises after sweating or purging therapies due to Stomach deficiency. The *Lei Zheng Huo Ren Shu* treats this as deficiency-cold, hence using various warming and tonifying drugs. However, there are also cases of deficiency with heat and excess with heat; the cited Ju Pi Zhu Ru Tang does not exhaustively cover all scenarios.