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In Zhang Zhongjing's writings, there is a distinction between "turbid saliva" (zhuo tuo) and "thin saliva" (xian tuo). The term "thin saliva" is sometimes referred to by later authors as "dan tuo" (light/thin saliva). The character "dan" describes its thinness, used to distinguish it from turbid saliva. Removing the water radical (氵) from the character "dan" yields the character for "phlegm" (tan). From *Zhubing Yuanhou Lun* (General Treatise on the Causes and Symptoms of All Diseases) by Chao Yuanfang onwards, all forms of saliva were termed "phlegm," even those that were not thin; they were called phlegm rather than saliva. For instance, coagulated saliva was called "glutinous phlegm" (jiao tan), and sticky saliva was called "greasy phlegm" (ni tan); both contradict ancient texts. However, ancients named diseases based on visible characteristics. Thin saliva is called "dan" because the quality of being "thin/light" is visible. If there is no visible "thinness," how can it be named "dan"? Therefore, it can be inferred that in the *Jingui Yaolue* (Essential Prescriptions of the Golden Cabinet), among the Four Types of Fluid Retention (Si Yin), the "Tan Yin" (Phlegm-Fluid), although some versions write it as "Dan Yin," refers to water flowing in the intestines. Whether this fluid is thin or thick is uncertain, yet Zhang Zhongjing would not have named it arbitrarily. The "Dan" in "Dan Yin" should be a scribal error for "Liu" (Flow). Flowing in the intestines precisely denotes its "flowing" nature. This parallels "Yi Yin" (Overflowing Fluid), "Xuan Yin" (Hanging Fluid), and "Zhi Yin" (Supporting Fluid), all of which differentiate fluid retention by the manner of water movement. The imagery of water movement requires these four terms to be complete. *Zhubing Yuanhou Lun* discusses fluid retention entirely based on *Jingui Yaolue*, but among the Four Types, it lacks "Dan Yin" and instead lists "Liu Yin." The symptoms listed for Liu Yin correspond exactly to the Dan Yin in *Jingui Yaolue*. The Sui dynasty version of *Jingui Yaolue* was correct; thus, Chao Yuanfang's account serves as definitive evidence. *Qianjin Yifang* incorporated Liú Yin into five categories, changed Xuan Yin to "Yan Yin," and Zhi Yin to "Dan Yin," while also describing fluid with audible movement in the intestines as "Liu Yin," aligning with Chao's view. Since the character "Liu" resembles "Dan," a transcription error occurred, which was subsequently altered to "Tan" (Phlegm), leaving obvious traces. Recently, some who superficially understand philology argue that since the character "Tan" contains the radical "Yan" (flame), the disease must belong to Fire. Treating according to such theory would be a grave error. Such distinctions must be examined with utmost care!

A pulse that rises and falls alternately on the left and right sides is called the "Scattered Pulse" (San Mai), resembling the motion of leaves or the falling of elm seeds. (*Yuyan Jing* states: "Rustling like falling elm seeds is named Scattered Pulse." *Nan Jing·81st Difficulty* writes "Yan Yan Nie Nie." Based on meaning, it should be "Qi Qi"; *Guang Yun* defines Qi Qi as the appearance of moving leaves.) It is like a light object floating on water (*Su Wen* states: "The Autumn pulse comes rapid and goes scattered, hence it is called Floating; similarly, like an object floating, it indicates Death of the Lung."), or like looking at a carriage canopy from afar (*Shanghan Lun* states: "A pulse vast and grand like a carriage canopy is named Yang Jie (Yang Knot)." *Nan Jing·81st Difficulty* considers this the normal pulse of the Lung.). The imagery is none other than these, hence the various analogies are employed. Alternating rise and fall resembles the Rapid Pulse (Shu Mai). However, the urgency of the Rapid Pulse is described longitudinally, whereas the rise and fall of the Scattered Pulse is described transversely; the Rapid Pulse's urgency forms a straight line, while the Scattered Pulse's undulation does not form a straight line—they are vastly different, hence it is said to resemble the Rapid Pulse. (*Su Wen* states: "The Winter pulse departs like a Rapid pulse," which precisely refers to the Scattered Pulse. The *Shi Cong Rong* chapter notes that Liver Stagnation with Deep Scattered pulse resembles Kidney pulse.) Furthermore, "like an object floating" refers to a Scattered Pulse that is adherent and combined with Excess; "like a carriage canopy" refers to a Scattered Pulse that is forceful and combined with Bigness. (*Su Wen* mentions "like an object floating, like wind blowing feathers." Cheng Wuji's commentary on *Shanghan Lun* explains "vast and grand like a carriage canopy" as large and rustling/weak.) Thus, one is the Pulse of Death of the Lung, and the other is the Pulse of Yang Jie; neither is the true image of the Scattered Pulse. Therefore, Zhang Zhongjing takes "falling like elm seeds" as the standard image. Moreover, since only the Scattered Pulse's rise and fall is described transversely, the Tight Pulse (Jin Mai) also shares the image of the Scattered Pulse. (Wang Bing's commentary on *Su Wen·Shi Cong Rong*: "Urgent, tight, and scattered is the Liver pulse.") Only because the Scattered Pulse's rise and fall does not form a straight line does the Surging Pulse (Hong Mai) also bear the name "Scattered." (*Nan Jing·81st Difficulty*: "Floating, large, and scattered is the Heart.") Extending these principles and applying them by analogy, the mastery of medical arts is complete.