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The *Shanghan Lun* (Treatise on Cold Damage) is a work dedicated to elucidating exterior and interior patterns. Since cold pathogenic factors invade the body in a sequential manner from exterior to interior, the text divides the disease process into six meridians (Six Channels) to delineate their chronological order. In the manifestation of cold damage diseases, exterior and interior patterns often coexist; therefore, the text is further divided into six chapters corresponding to the six meridians to distinguish the degree of such concurrent involvement. Consequently, in organizing terminology and narrating clinical events, it becomes necessary to establish a unified methodological principle. Cases presenting with pure exterior patterns are classified into the exterior section; those with concurrent interior patterns are also included in the exterior section; only cases presenting with pure interior patterns are placed in the interior section. For instance, if symptoms of all six meridians are present, they must be recorded in the Taiyang chapter, because Taiyang represents the most superficial layer of the exterior. Once Taiyang patterns resolve, the disease enters Yangming; once Yangming patterns resolve, it enters Shaoyang; once Shaoyang patterns resolve, it enters Jueyin, Shaoyin, and Taiyin. Each meridian’s presentation is categorized based on its most superficial layer. Thus, there are the most discussions regarding Taiyang, while Jueyin has the fewest. This is not due to negligence. Rather, according to the established principle, if other meridians’ patterns involve Taiyang, they cannot be discussed under their respective headings but rather under Taiyang. Conversely, if Jueyin patterns involve other meridians, they have already been distributed into their respective sections; thus, the Jueyin chapter merely records its specific meridian symptoms and the prognosis for resolution.

Regarding the content starting from the Sini Tang (Four Reversal Decoction) and subsequent formulas, ancient editions treated this as a separate chapter. The *Yuyuan Jing* (Jade Box Classic) titled it "Comprehensive Treatment of Vomiting, Hiccups, Cold Limbs, Diarrhea, Pulse, and Symptoms." The Song Benben (Song Dynasty Edition annotated by Cheng Wuji) erroneously merged it. Some scholars, relying on the Song edition, still found the content insufficient and, failing to understand the reason, claimed this was an unfinished work by Zhang Zhongjing, or alternatively, that it was disrupted by Wang Shuhe during compilation.

I have frequently argued that the Six Meridians in the *Shanghan Lun* serve to record the progression of exterior and interior patterns. What is the evidence? The answer lies in the theories of Hua Tuo. The *Qianjin Yaofang* (Essential Prescriptions Worth a Thousand Gold) cites his view: "Generally, in cold damage, on the first day the pathogen is in the skin, on the second day in the flesh/subcutaneous tissue, on the third day in the muscles, on the fourth day in the chest, on the fifth day in the abdomen, and on the sixth day it enters the Stomach." This classification into six layers to record the sequence of exterior and interior originated with Hua Tuo. What he termed "entering the Stomach" corresponds to Yangming disease characterized by Wei Jia Shi (Stomach House Excess/Intestinal Dryness-Heat Excess); "in the skin, flesh, and muscles" corresponds to Taiyang and Yangming meridian diseases; "in the chest" corresponds to Shaoyang and Taiyin diseases manifesting as vomiting and inability to ingest food; "in the abdomen" corresponds to Taiyin disease with abdominal fullness and pain, as well as Shaoyin and Jueyin diseases. The differences lie merely in the style of expression (literary vs. plain) and the granularity of the stages (detailed vs. condensed). However, the underlying meaning of recording the exterior-interior progression remains identical. Zhang Zhongjing retained the text from the *Suwen* (Basic Questions) regarding the transmission through six meridians over six days as a foundational principle, and further enriched it with Hua Tuo’s concept of six days and six layers, modifying the titles to establish the chapters. This reflects an intention to prioritize herbal therapy while simplifying acupuncture methods. Chao Yuanfang understood this, which is why the *Bingyuan* (Source of Diseases) preserved Hua Tuo’s theory in its general discussion and subsequently arranged the *Suwen*’s text on disease generation via pulses across six days and six meridians. This aligns perfectly with Zhang Zhongjing’s approach, providing further confirmation. What, then, is there to doubt?