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The manifestations of its diseases are recorded in extreme detail and completeness. Because the purport of the *Classic* (Neijing) is profound and extensive, it cannot be fully recorded here; this merely distinguishes between large and small tendons to elucidate the pathogenesis of shortening with spasm and relaxation with elongation. (From *Yixue Jieti*)

Tendons possess both rigidity and flexibility. The rigid ones bind the bones, while the flexible ones provide mutual support and connection. This is analogous to collaterals within meridians or threads within a net. Therefore, the tendons running straight along the limbs, vertex, and back that attach to the bones are firm and large; whereas the tendons branching horizontally across the chest, abdomen, head, and face are soft and fine. However, the tendons of the twelve meridities of the hands and feet differ from one another. For instance, the three Yang meridians of the hands and feet run on the exterior, so their tendons are mostly rigid; the three Yin meridians of the hands and feet run on the interior, so their tendons are mostly flexible. The tendons of the Foot Three Yin and Foot Yangming meridians all converge at the external genitalia. Thus it is said: "The anterior yin is the gathering place of the Zongjin (Major Tendons)." This represents the great convergence of tendons. (From *Leijing*)

Appendix: Nails
The *Classic* states: "The Liver harmonizes with the tendons; its flourishing manifests in the nails." Essentially, nails are the sprouts of the tendons, formed from the surplus Qi of the Liver. It is also stated: "Excessive consumption of sour flavor leads to tendon spasm and nail withering." Although sour flavor enters the Liver, excessive sourness causes nails to wither, while moderate sourness keeps them moist. Moisture indicates excess Liver Qi, while withering indicates depletion of Liver Qi. It is further stated: "The Gallbladder corresponds to the nails. Thick nails with yellow color indicate a thick Gallbladder; thin nails with red color indicate a thin Gallbladder; hard nails with blue-green color indicate urgent Gallbladder Qi; soft nails with red color indicate relaxed Gallbladder Qi; straight nails with white color and no lines indicate upright Gallbladder Qi; ugly nails with black color and many lines indicate knotted Gallbladder Qi." It is also stated: "When the upper part of the Foot Shaoyang Meridian is affected by cold-dampness, it predisposes to Bi syndrome, bone pain, and nail withering." Since the Foot Shaoyang belongs to the Gallbladder, and the Liver and Gallbladder share the same palace (interior-exterior relationship), their signs are thus similar. (From *Yixue Jieti*)

Appendix: Skin
The *Ling Shu* states: "The Lung corresponds to the skin. Thick skin indicates thick Large Intestine; thin skin indicates thin Large Intestine; loose skin with a distended abdomen indicates a large and long Large Intestine; tight skin indicates an urgent and short Large Intestine; smooth skin indicates a straight Large Intestine; skin and flesh firmly adhered without separation indicate a knotted Large Intestine. The Heart corresponds to the vessels. Thick skin indicates thick vessels; thin skin indicates thin vessels; loose skin indicates relaxed vessels. The Kidney corresponds to the bones. Dense texture with thick skin indicates thick Sanjiao and Bladder; coarse texture with thin skin indicates thin Sanjiao and Bladder; tight skin without hair indicates urgent Sanjiao and Bladder." It is also stated: "Humans have three constitutions: Fei (Fat), Gao (Pasty), and Rou (Muscular). Firm muscle with full skin is Fei; non-firm muscle with loose skin is Gao; skin and flesh firmly adhered without separation is Rou." From this, we can deduce that observing the skin has its own principles. Geographically, people born in the South have soft and fragile skin; people born in the North have strong and thick skin. Thus, skin varies by local environment. Socially, nobles and officials have soft and fragile bodies; the poor and laborers have strong and thick skin. Thus, skin varies by nourishment. Scholars who understand this can discuss the reversal or smoothness of form and Qi, and the conditions of excess or deficiency. (From *Yixue Jieti*)

Just as the essence and Qi of trees ascend through the bark, the essence and Qi of the human body reach the exterior through the Couli (interstices). Among the forms, only the skin is prone to death but also quick to regenerate. If sweat does not penetrate, the skin dies; hence, after illness, the skin peels, and severely, hair falls out. Even more severely, nails may shed, muscles waste away, and bones become flaccid, which are events associated with severe diseases. Skin regenerates easily; thus, even in mild cases of skin peeling, it occurs. Peeling skin heals spontaneously without treatment; fallen hair and shed nails recover with conditioning; wasted muscles and flaccid bones require potent tonification to recover. (From *Yican*)

Appendix: Muscles
The *Classic* states: "The Yangming Meridian governs the surface of the muscles." It also states: "Abundant Qi and Blood fill the skin and warm the muscles; if Blood alone is abundant, it渗 (seeps) into the skin, generating hair." There are distinct differences among muscle layers. The entire human body consists externally of hair and skin, internally of muscle and flesh, and further includes meridians, fatty membranes, bones, and tendons. What is called 'Zhi' (fat) is the grease near the muscle. What is called 'Ji' (muscle proper) is the tender grease connected to the skin. Zhi permeates the interior, being fatty and void; Ji connects to the skin, being tender and solid. Solidity makes the skin firm; tenderness makes the skin moist. Generally, beautifying the body's magnificent shell lies in moistening the muscle and shining the skin, and the function of moistening and shining depends on nourishing Ying and Wei Qi. Therefore, there are conditions such as rice-grain-like bumps in muscle, emaciated muscle, cold muscle, and hot muscle. Although muscle is superficial, each disease has its specific cause. Why do people simply say that diseases in muscle and skin are exterior syndromes! (From *Yixue Jieti*)

Bone, tendon, fatty membrane, muscle, skin, and hair—these ten elements are what humans borrow to form their shape. Bone is the root; tendons bind the bones; membranes wrap the tendons; fat consolidates the membranes; muscles guard the fat; muscle nourishes the meat; skin governs the muscle; skin flourishes the skin; hair protects the skin; fine hair assists the hair. It is like a house: bone serves as beams and pillars; tendons serve as hinges; fatty membranes and muscles serve as walls; skin and hair serve as doors and windows, filling the gaps in the walls. Any damage leads to a dilapidated house; any injury leads to collapse. (From *Yican*)

Appendix: Flesh/Muscle
The *Classic* states: "The Spleen governs the flesh. In the body, it manifests as flesh; in the zang organs, it corresponds to the Spleen." A person's robust physique throughout life stems from sufficient endowment; congenital emaciation belongs to insufficient innate True Yuan. Middle-aged obesity results from excessive nourishment; late-life vitality arises from guarding the True Yuan. All these are evidenced by the state of the flesh. Does not the *Classic*'s statement that "flesh acts as a wall" warrant verification? Regarding treatment, one must examine the cause. Dampness injures the flesh; Wind overcomes Dampness. Sweet flavor injures the flesh; Sour overcomes Sweet. Prolonged sitting injures the flesh. Physical ease and mental joy lead to diseases arising in the flesh. Pathogenic factors in the Spleen and Stomach result in muscle pain; overflowing pathogens and stagnant Qi cause heat in the pulse and failure of the flesh. Thus, regulation and maintenance involve many methods. (From *Yixue Jieti*)

Appendix: Couli (Interstices)
The *Ling Shu* states: "Couli vent, causing profuse sweating." It also states: "Wei Qi warms the fenrou (divided muscles), fills the skin, plumps the Couli, and controls opening and closing." Hence, they are called Yuanfu (Original Gates) and Guimen (Ghost Gates). There is also discussion of open Couli and massive sweating. Sweat and grime exit here; wind pathogens enter here. Every hair follicle on the body has an orifice, which is the boundary of the Couli. Closed Couli prevent external pathogens from entering; open Yuanfu facilitate sweating. Southerners value cleanliness, so their Yuanfu and Guimen open easily; Northerners bathe infrequently, so grime and oil protect the Couli, preventing easy invasion by pathogens and making sweating difficult. However, individual constitutions vary, and sometimes North and South are reversed; one need not rigidly adhere to a single theory. (From *Yixue Jieti*)

Appendix: Orifices
Humans have nine orifices, actually thirteen. The tongue is the Heart orifice; Lianquan is the fluid orifice; Guimen (sweat pores) is the sweat orifice; the penis is the essence orifice. Combined with the nine standard orifices, there are thirteen. (From *Yican*)

The obstruction or smoothness of Qi in the human body is consistent with the principles of the *I Ching*. Earth over Heaven constitutes Tai (Peace); Heaven over Earth constitutes Pi (Stagnation). Two ear orifices, two eye orifices, and two nasal orifices combine to symbolize the Kun trigram (Earth). Below the nose lies the middle of the human body. One mouth orifice, one anterior yin orifice, and one posterior yin orifice combine to symbolize the Qian trigram (Heaven). From the head to the lips is motionless, representing the Earthly Dao. From the mouth to the feet is mobile, representing the Heavenly Dao. The head is above as Heaven, the feet are below as Earth; the upper and lower parts of the human body combine, allowing for upright standing. Going against this leads to Tai (smoothness/peace), following it leads to Pi (stagnation/blockage), which is the natural order. People simply fail to observe this. ○ Master Wang said: Horizontal orifices have Qi moving in and out; vertical orifices have Yin and Yang ascending and descending. The nine upper and lower orifices, plus eighty-four thousand external hair pores, are all gates for Qi. (From *Wu Yi Hui Jiang*)