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Books on pulse diagnosis are most meticulous in the works of Li Binhu (Li Shizhen) and Zhu Danxi. They can clearly distinguish between similar yet distinct pulses, using writing to depict and compare their shapes, thereby preventing students from making misidentifications. This can be said to be a great contribution to the world. Alas, regarding the method of tongue inspection, these two masters did not write specialized books. What is circulated in the world are only *Shanghan Shejian* (Tongue Diagnosis of Cold Damage) and *Wenyi Shejian* (Tongue Diagnosis of Pestilential Diseases). To find a tongue diagnosis text as detailed as those on pulse diagnosis is impossible.

I have devoted myself to this for over thirty years, recording cases where diagnostic trials and treatments were effective and accurate without error, in notebooks to teach my disciples, daring not to consider myself correct. In the Gengxu year, Mr. Yuan Guisheng and other colleagues in Zhenjiang founded the *Yixue Fulun Bao* (Medical Wheel Support Newspaper) to promote medicine. I joined them, sharing the responsibilities of printing costs and content provision. By the winter of the Gengxu year, many had the intention to withdraw, leading to a lack of funds and content, threatening to halt the project midway. I was merely filling a quota, and the printing was unfinished. By August of the Xinhai year, our *Fulun Bao*, along with us, underwent revolution simultaneous with the fall of the Qing Dynasty. Now, members of the Shaoxing Medical Association and Shanghai Medical Association who have read the newspaper often write to Mr. Yuan and Mr. Yang requesting the complete manuscript. These are old friends who read the *Fulun Bao*, not discarding my humble views because they are insignificant. It seems that my descriptive analogies still have some merit. Therefore, following their advice, I copied the entire manuscript, added a preface, and sent it to the *Shaoxue Yixue Bao* society. Following Mr. Zhou Xiaonong’s method of circulating books, this is also an effort to throw a brick to attract jade. This is the preface. I humbly request guidance from all distinguished experts to correct my deficiencies, which would be my greatest fortune.

In the spring equinox, three days after, in the year Gengxu, Liu Hengrui wrote this preface at Tingyun Guesthouse, Youyu Studio, Jingjiang.

The tongue is the external manifestation of the Stomach, used for transporting food into the esophagus and stomach. The tissue of the tongue body is reached by the fifth cranial nerve, and its function relies entirely on the movement of this nerve. The two purple-blue veins under the tongue are the Shaoyin Kidney meridian ascending, named the acupoints Jinjin (Golden Spring) and Yuye (Jade Fluid), which generate saliva to moisten the tongue substance. If one does not understand these principles, the understanding of syndrome differentiation will inevitably suffer from a slight initial error leading to a massive deviation later; thus, these principles must be studied.

The surface of the tongue is covered with numerous tiny papillae, raised but not easily visible. Because people eat three meals a day, the tongue coating changes three times a day, called "living coating," which is a sign of health. The reason for these changes is that when food enters the stomach, turbid qi is suppressed and descends, causing the coating color to fade; when food decomposes, turbid qi steams upward, causing the coating color to reappear. If there is no turbidity in the Stomach, the coating is thin and scanty; if there is turbidity, the coating is thick and abundant. The true color of the Stomach cannot directly reach the surface, so the coating may temporarily appear white. Green is the color of extremity/despair; if green or bluish-green appears on the tongue, the person's life is in danger. Additionally, various intermediate colors such as yellow-like-but-not-yellow and white-like-but-not-white are listed separately below for careful reference by future students.