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Currently, it is generally believed that the collaterals (络脉, luò mài) are small branches of the meridians (经脉, jīng mài), which can be classified into bie luo (别络, secondary collaterals), sun luo (孙络, minor collaterals), and fu luo (浮络, superficial collaterals). The bie luo consists of fifteen branches, hence referred to as the fifteen collaterals. According to the “Zhen Jiu Ji Cheng” (针灸集成), it states: “The collaterals of the fifteen collaterals are those that connect the yin meridians to the yang meridians, and the yang meridians to the yin meridians, traversing between the two meridians, which is what is referred to as the collaterals.” According to the “Ling Shu: Jing Mai” (灵枢·经脉), these fifteen collaterals consist of one collateral from each of the twelve meridians, one from the Ren (任脉) and one from the Du (督脉), plus the major collateral of the Spleen (脾). If we also include the major collateral of the Stomach (胃), it is referred to as the sixteen collaterals.The collaterals are a collective term for the branched parts that diverge from the meridians. The “Ling Shu: Mai Du” (灵枢·脉度) states: “The meridians are the interior, while those that branch out and traverse are the collaterals, and the branches of the collaterals are the sun collaterals.” The term “collateral” implies a network, as they branch out from the meridians, becoming increasingly numerous and finer, forming a network throughout the body, reaching every part.1. Main Lines of the CollateralsThe main lines of the collaterals that branch out from the meridians can be divided into two major categories: one type is the “bie luo” that branches from the acupoints on the surface of the body, and the other type is the “da luo” (大络, major collaterals) that branches from the internal meridians. Both serve as important pathways for the qi and blood to nourish the internal and external tissues and organs, complementing each other and being indispensable, collectively referred to as the major collaterals.1. Bie Luo The bie luo are the main lines of the collaterals that branch from the acupoints on the meridians, connecting to the corresponding meridians. There are fourteen branches of bie luo, corresponding to the twelve meridians plus one each from the Ren and Du meridians, referred to as the fourteen collaterals. It is worth mentioning that the major collateral of the Spleen and Stomach is derived from the internal meridians and should not be included in this count. As Wang Bing commented in his annotations to the “Su Wen: Qi Xue Lun” (素问·气穴论篇), “The fourteen collaterals refer to the twelve collaterals, plus the collaterals of the Ren and Du meridians. The major collateral of the Spleen originates from the Spleen (referring to the Spleen meridian), hence it is not included in this count.” The fourteen collaterals primarily run in the superficial parts of the body, branching out from the acupoints below the elbow and knee joints, connecting to the corresponding meridians, thus the bie luo of the yin meridians connect to the yang meridians, and the bie luo of the yang meridians connect to the yin meridians, maintaining a close relationship between the two meridians. Therefore, the bie luo strengthens the connection between the twelve meridians on the surface of the body and can reach certain areas that the primary meridians do not, compensating for the deficiencies of the primary meridians.2. Da Luo The da luo are the main lines of the collaterals that branch from the internal meridians, primarily connecting with the internal organs. Each of the five zang (五脏, solid organs) and six fu (六腑, hollow organs) has its own da luo, serving as pathways for the qi and blood to nourish the organ tissues. As stated in the “Ling Shu: Yu Ban” (灵枢·玉版), “The qi and blood that emerge from the Stomach are the pathways of the meridians. The pathways of the meridians are the major collaterals of the five zang and six fu.” Historical literature has not systematically discussed the da luo of the five zang and six fu, nor has it been comprehensive. For example, the “Ling Shu: Ni Shun Fei Shou” (灵枢·逆顺肥瘦) mentions: “The Chong Mai (冲脉) injects into the da luo of the Shao Yin (少阴) and emerges from the Qi Jie (气街).” Clearly, the term “da luo of the Shao Yin” is not the same as the “bie luo of the Zu Shao Yin (足少阴)”. This indicates that the da luo of the Zu Shao Yin branches out from the internal Zu Shao Yin meridian. The “Nei Jing” (内经) provides a detailed description of the da luo of the Spleen and Stomach. The “Ling Shu: Jing Mai” states: “The major collateral of the Spleen is called Da Bao (大包). It emerges three inches below the armpit and spreads across the chest and ribs.” The “Su Wen: Ping Ren Qi Xiang Lun” (素问·平人气象论篇) states: “The major collateral of the Stomach is called Xu Li (虚里), which connects the diaphragm and links to the lungs, emerging below the left breast.” The major collateral of the Spleen emerges “three inches below the armpit”, and the major collateral of the Stomach emerges “below the left breast”. Both are derived from the internal meridians. Wang Bing answered the question of where they branch out from: “The major collateral of the Spleen originates from the Spleen.” Therefore, the major collaterals of the Spleen and Stomach branch from the Spleen and Stomach meridians. Referring to the major collateral of the Stomach, which “connects the diaphragm and links to the lungs”, although the major collateral of the Spleen is not explicitly stated, it can be inferred that it primarily connects with the internal organ tissues.The bie luo and da luo are the main lines of the collaterals that branch from the meridians, and they are larger components of the collaterals, collectively referred to as the major collaterals. Currently, the bie luo, also known as the da luo, has a clear direction and pathway, totaling fifteen, also known as the fifteen bie luo. If we include the major collateral of the Stomach, there are a total of sixteen collaterals. The principle is that the twelve meridians and the two meridians of the Du and Ren are collectively referred to as the fourteen primary meridians, which are the main lines of qi and blood circulation. Thus, the bie luo of the fourteen primary meridians nourish the body with qi and blood, forming the main lines of the collaterals. Since the fourteen bie luo primarily run in the superficial parts of the body, they are easy to observe, hence their direction and pathway are clear. Additionally, the Spleen is responsible for the transportation of fluids, and the Spleen and Stomach together form the foundation of postnatal life, the source of qi and blood transformation, making the major collaterals of the Spleen and Stomach also very important main lines of the collaterals. Therefore, the bie luo of the fourteen primary meridians and the major collaterals of the Spleen and Stomach are collectively referred to as the sixteen collaterals.2. Hierarchy of the CollateralsThe collaterals are branches that diverge from the meridians, and after branching from the meridians, they further subdivide into a hierarchical network consisting of major collaterals (bie luo or da luo) down to sun luo (孙络, minor collaterals), forming a layered system known as the collateral system. The “Ling Shu: Mai Du” states: “The meridians are the interior, while those that branch out and traverse are the collaterals, and the branches of the collaterals are the sun collaterals.” After the “Nei Jing”, subsequent generations of physicians have further supplemented and discussed the hierarchy of the collaterals, making it more comprehensive. In the Jin Dynasty, Dou Hanqing in his “Zhen Jing Zhi Nan” (针经指南) stated: “There are fifteen collaterals, over three hundred horizontal collaterals, eighteen thousand silk collaterals, and an unknown number of sun collaterals.” This indicates that the collaterals have different levels, including bie luo, horizontal collaterals, silk collaterals, and sun collaterals. The Ming Dynasty acupuncture text “Ren Jing Jing” (人镜经) states: “The twelve meridians give rise to fifteen collaterals, the fifteen collaterals give rise to one hundred eighty system collaterals, the system collaterals give rise to one hundred eighty entangled collaterals, and the entangled collaterals give rise to thirty-four thousand sun collaterals.” This adds system collaterals and entangled collaterals to the network hierarchy of the collaterals. In the Qing Dynasty, Yu Jiayan inherited the teachings of the “Ren Jing” and further described the hierarchy of the collaterals in his “Yi Men Fa Lu: Luo Mai Lun” (医门法律·络脉论): “The twelve meridians give rise to twelve collaterals, the twelve collaterals give rise to one hundred eighty system collaterals, the system collaterals branch into one hundred eighty entangled collaterals, and the entangled collaterals branch into thirty-four thousand sun collaterals, with entanglements between the sun collaterals.” This clearly states that the collaterals that branch from the meridians are divided into major collaterals, which are further subdivided into system collaterals, entangled collaterals, and sun collaterals.The sun luo are the smallest collaterals, belonging to the further branches of the collaterals, and are the smallest units of the collaterals, distributed throughout the body and difficult to count. Moreover, the sun luo are interconnected and have significant implications. The twelve meridians, “yin and yang interpenetrate, like a ring without end”, serve as the linear pathways for qi and blood circulation, while the collaterals, which are progressively subdivided from the meridians, have entanglements between the sun luo at their ends, forming a planar interconnection, thus constituting a networked life support system that maintains the normal functional activities of the body, primarily serving to nourish the organ tissues with qi and blood and to defend against pathogenic factors. As stated in the “Su Wen: Qi Xue Lun” (素问·气穴论篇), it is referred to as “overflowing of qi pathogens” and “communicating the nutritive and defensive qi”.Additionally, the collaterals distributed on the surface of the skin are referred to as “fu luo” (浮络), which are described in the “Ling Shu: Mai Du” as “the collaterals that are floating and commonly seen”, widely distributed without specific localization, serving to connect the meridians and deliver to the muscle surface; the collaterals visible on the superficial skin are referred to as “xue luo” (血络), which in pathological states refer to the collaterals in the superficial skin layer that have blood stasis. Thus, Zhang Zhichong in his “Huang Di Nei Jing Ling Shu Ji Zhu: Xue Luo Lun” (黄帝内经灵枢集注·血络论) states: “The blood collaterals are the external collaterals and sun collaterals, seen between the skin; if the blood and qi accumulate, it will lose its mechanism of internal and external exchange.”3. Location of the CollateralsThe collaterals crisscross and connect to form a network, with distribution categorized into external and internal. The external ones are called yang collaterals (阳络), while the internal ones are called yin collaterals (阴络). For instance, in the Ming Dynasty, Zhang Jiebin in his “Liu Jing” (类经) stated: “In terms of collaterals, there are also major collaterals and sun collaterals, with distinctions between internal and external; the deep ones are internal, which are yin collaterals… the superficial ones are external, which are yang collaterals.” Wang Yongyan also proposed: “The collaterals have distinctions between yang collaterals and yin collaterals.” It can be seen that the spatial distribution of the collaterals in the body presents a pattern of external (such as the floating collaterals on the surface being yang collaterals), middle (the meridians), and internal (the major collaterals of the internal organs being yin collaterals).1. Yang Collaterals Yang collaterals refer to the collaterals that branch out from the meridians and are distributed on the surface of the body. Yang collaterals are those that are visible on the surface, such as the “Ling Shu: Jing Mai” states: “All the collaterals that are floating and commonly seen are collaterals” and “all the visible collaterals are collaterals.” According to the “Su Wen: Pi Bu Lun” (素问·皮部论篇), “The skin has divisions”, the twelve meridians delineate the skin into twelve skin areas, where the qi and blood of the twelve meridians are distributed on the surface. The skin areas are filled with collaterals that branch out from the corresponding meridians and float on the surface, such as the Yangming skin area being filled with collaterals of the Yangming meridian. As stated in the “Su Wen: Pi Bu Lun”: “The yang of Yangming is called Hai Fei, and the upper and lower follow the same method; observe that there are floating collaterals in this area, all of which are collaterals of Yangming.” The floating collaterals of the twelve meridians on the surface of the body participate in the composition of the skin area, and the qi and blood of the twelve meridians warm, nourish, and protect the skin through the collaterals. Therefore, the “Su Wen: Pi Bu Lun” also states: “The collaterals of the twelve meridians are all part of the skin area.” Yang collaterals are not only an important structure of the collaterals, participating in the composition of the skin area, but also serve as an important window for the occurrence, diagnosis, and treatment of diseases. For example, the “Ling Shu: Bai Bing Shi Sheng” (灵枢·百病始生) systematically discusses how “deficiency pathogens” emerge from the skin and gradually progress from the surface to the interior, ultimately leading to “cessation and accumulation” of diseases, and also mentions that “injury to the yang collaterals can lead to bleeding on the surface and mucous membranes”. The “Nei Jing” records a wealth of diagnostic methods for the collaterals and numerous applications of bleeding techniques, massage methods, and external treatments through yang collaterals to treat various diseases.2. Yin Collaterals Yin collaterals refer to the collaterals that branch out from the meridians and are distributed within the internal organ tissues. Yin collaterals are those that circulate within the body, spreading throughout the organs, thus becoming the collaterals of the organs. For instance, Ye Tianshi in his “Lin Zheng Zhi Nan Yi An: Bian Xue” (临证指南医案·便血) recorded that “yin collaterals are the collaterals beneath the organs.” The collaterals that branch out from the twelve meridians and are progressively subdivided circulate and distribute in the organ areas, becoming an organic part of the structure of the organs. The qi and blood of the twelve meridians nourish and connect the five zang and six fu through these collaterals (yin collaterals), adjusting the balance of yin and yang in the organs. The qi and blood generated from food entering the Stomach circulate through the meridians and enter these collaterals (yin collaterals), distributing to the five zang and six fu, forming the essence of the five zang and six fu. As stated in the “Ling Shu: Yu Ban”: “The qi and blood that emerge from the Stomach are the pathways of the meridians; the pathways of the meridians are the major collaterals of the five zang and six fu.” Yin collaterals are also an important structure of the collaterals, forming an organic part of the organ structure, connecting the organs, and nourishing the qi and blood, allowing the refined essence from the Spleen and Stomach to be distributed to the five zang and six fu. This is the physiological basis of the theory that “the Spleen does not govern time” in the “Su Wen: Tai Yin Yang Ming Lun” (素问·太阴阳明论篇). At the same time, they are also important pathways for the transmission of diseases and treatment of diseases. For example, Ye Tianshi in his “Wen Re Jing Wei: Ye Xiang Yan Wai Gan Wen Re Pian” (温热经纬·叶香岩外感温热篇) recorded that “when warm pathogens invade, the first choice is to affect the lungs”, and if the heat in the meridians does not resolve, it can “reverse and transmit to the pericardium”. In the “Lin Zheng Zhi Nan Yi An: Wen Re”, it is also stated: “Inhaling warm pathogens, the nose connects to the lung collaterals, reversing and transmitting to the pericardium”. Furthermore, in discussing the external pathogens entering from the surface to the interior, or internal injuries and difficult miscellaneous diseases, it is clearly proposed that “chronic diseases enter the collaterals” and “chronic pain enters the collaterals”, indicating that “initially, qi is blocked in the meridians, but over time, blood is injured and enters the collaterals”, revealing a common pattern in the progression of diseases and establishing a system of transmission and differentiation of warm diseases based on the relationship between defensive qi, nutritive qi, and blood.4. Morphology of the CollateralsThrough the study of historical literature, it has been found that collaterals can be divided into qi collaterals and blood collaterals, and it is believed that the meridian system consists of two major systems: the qi vessel system and the blood vessel system. The qi vessel system is the main pathway for the movement of qi, including qi vessels and qi collaterals. The movement of formless qi and the sensory transmission of the meridians are primarily accomplished through the qi vessel system; the blood vessel system is the main pathway for the circulation of blood, including blood vessels and blood collaterals. The circulation of tangible blood, nutritive qi, etc., is accomplished through the blood vessel system. The study of the meridian and blood vessel systems has a long history. The “Ling Shu: Jing Shui” (灵枢·经水) states: “The meridians receive blood and nourish it.” In the Qing Dynasty, Shi Shoutang in his “Yi Yuan” (医原) directly linked the meridians with the heart, stating: “The meridians throughout the body all root in the heart, and connect to the lungs above, returning below, like a tree with roots, trunk, and branches. The entire body, one qi flows through, circulating blood vessels, allowing for mutual exchange, hence the “Nei Jing” states: “The heart generates blood”. It also states: “All the vessels belong to the heart”. Clearly, the meridians referred to here are those that have the function of carrying blood to nourish the body.Due to the formless and difficult-to-detect nature of qi, research on the qi vessel system has been delayed. The term “qi vessel” originates from the “Nei Jing”, which states: “Those who live beyond their natural lifespan have a constant flow of qi vessels, and the kidney qi is abundant.” This “qi vessel” refers to the meridians and collaterals that primarily function to carry and circulate qi. In the Ming Dynasty, Zhang Jiebin proposed the concept of “qi collaterals” based on the “qi vessels” in the “Nei Jing”, stating in his “Liu Jing”: “Blood vessels are internal, while qi collaterals are external.” By juxtaposing blood vessels and qi collaterals, the meanings of meridians and collaterals are mutually inclusive, encompassing both the meridians and collaterals, meaning that blood vessels include blood meridians and blood collaterals, while qi collaterals include qi meridians. In the Qing Dynasty, Zhou Xuehai further clarified the concepts of qi vessels and blood vessels, stating in his “Du Yi Sui Bi” (读医随笔): “The nutritive qi emerges from the Spleen and Stomach, nourishing the tendons, bones, muscles, and skin, filling and circulating within the blood vessels without moving. The ancestral qi is the combined essence of the nutritive and defensive qi, emerging from the lungs, accumulating in the qi sea, circulating within the qi vessels, moving and exchanging.” This outlines the embryonic form of the qi vessel and blood vessel systems.
Disclaimer: This article is selected from the Journal of Liaoning University of Traditional Chinese Medicine, November 2007, Issue 6, by author Wang Jin. The articles shared by this public account are for reference and learning purposes only. If there are any improper uses of the published content, please feel free to contact us for deletion. Please retain copyright information when reprinting. All treatment methods, formulas, and medicines mentioned in the text are for learning reference only and should be used with caution by non-professionals.