Besides the twelve regular channels, Chinese medical theory describes eight vessels that run outside their system: the governor vessel (du mai), the conception vessel (ren mai), the thoroughfare vessel (chong mai), the belt vessel (dai mai), the yin and yang heel vessels (yin qiao mai and yang qiao mai) and the yin and yang link vessels (yin wei mai and yang wei mai). The English names are those of the WHO’s International Standard Terminologies on Traditional Medicine in the Western Pacific Region (2007), which calls the eight the “eight extra meridians”. Two classical texts set out what they are for, and they disagree on how qi reaches them: the Nanjing, the Classic of Difficult Issues, and Li Shizhen’s Exposition on the Eight Extraordinary Vessels of the 1570s.
Why “extraordinary”
The word is qi (奇), which commentators have read in more than one way. Charles Chace and Miki Shima, in the introduction and commentary to their translation of Li Shizhen’s Exposition, quote Li’s own explanation, which he took from the 27th issue of the Nanjing: the eight “are not controlled by the 12 main channels, nor are they arranged in exterior-interior combinations, and therefore they are called extraordinary”. The Tang commentator Yang Xuancao read qi as “odd or unpaired”; the Song commentator Yu Shu objected and read it as fundamental and singular. On each reading the vessels stand outside the pairings that bind the twelve channels.
The eight vessels
The WHO terminology defines each vessel by its course. Only the governor and conception vessels carry points of their own: the WHO counts them with the twelve regular channels as the fourteen meridians, and defines channel points as points of a main meridian or of the governor or conception vessel. The other six have no points of their own.
| Vessel | Chinese | Course |
|---|---|---|
| Governor vessel (du mai) | 督脈 | from the lower abdomen, emerges at GV01 (Changqiang) behind the anus and sends a branch forward to CV01 (Huiyin); rises along the midline of the back over the top of the head and down the midline of the face to GV28 (Yinjiao) inside the upper lip |
| Conception vessel (ren mai) | 任脈 | from the lower abdomen, emerges at CV01 in the perineum and rises along the midline of the abdomen and chest to CV24 (Chengjiang) below the lower lip; an internal branch encircles the mouth and reaches the eyes, and another rises along the spine to the throat |
| Thoroughfare vessel (chong mai) | 衝脈 | from the lower abdomen, emerges at the perineum, joins the kidney channel and rises along both sides of the abdomen to the chest |
| Belt vessel (dai mai) | 帶脈 | from the lower edge of the ribs, circles the waist |
| Yin heel vessel (yin qiao mai) | 陰蹻脈 | from the inner heel up the inner leg, through the genitals, abdomen, chest and neck and beside the nose to the eye |
| Yang heel vessel (yang qiao mai) | 陽蹻脈 | from the outer heel up the outer ankle and leg, through the abdomen, chest, shoulder and cheek to the back of the neck |
| Yin link vessel (yin wei mai) | 陰維脈 | from above the inner ankle up the inner leg, through the abdomen, chest and throat to the back of the neck |
| Yang link vessel (yang wei mai) | 陽維脈 | from below the outer ankle up the outer leg, along the side of the trunk, over the shoulder and neck to the top of the head |
AcuiQ’s catalogue gives the governor and conception vessels pages of their own, and
The channel system, counted places them among the
fourteen channels. GB26 on the gallbladder channel
carries the belt vessel’s name, Daimai.
The theory ties the thoroughfare and conception vessels to menstruation and pregnancy. The WHO terminology gives “sea of blood” as a name for the thoroughfare vessel, and names pathologies of the two vessels together, among them their failure “to control menstruation and prevent uterine bleeding and abortion”.
The Nanjing: reservoirs for overflow
The 27th and 28th issues of the Nanjing describe the vessels with an image of irrigation. In the translation Chace and Shima give, the sages “constructed irrigation ditches and kept the waterways open so that they would be prepared for any extraordinary situation”, and when the ditches were full the excess “flowed into deep lakes”. The twelve channels are the ditches and the eight vessels the lakes. Chace and Shima note that in this scheme the flow runs one way: the network vessels take the overflow of the main channels, the extraordinary vessels take the overflow of the networks, and nothing returns. The symptoms the Nanjing attaches to the vessels are, in Chace and Shima’s summary, mostly conditions of excess, such as stiffness of the lower back, chest pain, abdominal urgency and masses, and the only treatment the Nanjing gives is to pierce the affected vessel with a sharp stone.
Li Shizhen: a two-way flow
Li Shizhen’s Exposition on the Eight Extraordinary Vessels (Qi jing ba mai kao) was published between 1576 and 1578, with prefaces dated 1572 and 1577, and the earliest surviving edition dates from 1606. Chace and Shima, whose 2010 translation is the first into English, describe the Exposition as a cornerstone of the literature on the vessels. Li wrote for two readers at once, physicians and Daoist practitioners of internal cultivation, and drew on both literatures. He opens with the Nanjing’s irrigation image but changes its direction: overflow from the channels enters the extraordinary vessels and returns, “providing reciprocal irrigation, interiorly warming the yin viscera and yang receptacles, and exteriorly moistening the interstices”. Chace and Shima call that reciprocal flow Li’s own innovation, and report that it has become the standard understanding of how the vessels relate to the rest of the channel system.
The confluent points
Modern practice reaches the vessels through eight points, which the WHO terminology calls the confluence points of the eight vessels: “points where the main meridians communicate with the eight extra meridians”. Chace and Shima trace the formularies built on them, which they call the master-couple holes, to texts compiled after Li, above all Yang Jizhou’s Grand Compendium of Acupuncture and Moxibustion (Zhenjiu dacheng) of 1601, and describe them as the basis of most modern extraordinary vessel therapeutics. Li himself ignored them. The influential and confluent points lists the eight points. The WHO also records a timed method, the eightfold method of the sacred tortoise (linggui bafa), which selects among the confluent points according to the eight trigrams, the heavenly stems and earthly branches.
What research has tested
Ted Kaptchuk’s 2002 review in Annals of Internal Medicine classes the concepts of the
traditional theory, qi among them, as East Asian conceptual frameworks that many physicians who practise
acupuncture reject as prescientific. Trials have tested point selections built on the vessels. In a
2010 trial by Zhao and Fan at Guangxi University of Chinese Medicine, 60 people with
chronic superficial gastritis diagnosed as a liver-stomach disharmony pattern were randomised to the
linggui bafa method with PC06 (Neiguan) and
LV03 (Taichong), or to a routine prescription that included
ST36 (Zusanli), CV12
(Zhongwan), LV03 and PC06. The authors report their best grade of response on clinical assessment in 20 of 30
people against 8 of 30, and on gastroscopy in 20 of 30 against 7 of 30. The trial is small, the abstract does not report
blinding, and it compares one acupuncture prescription with another rather than with sham.
Qi, blood and body fluids reports a 2008 review of the
search for the channels in the electrical properties of the skin.
What the sources cannot tell you
The two classical accounts describe different systems: one-way reservoirs in the Nanjing, a reciprocal circulation in Li, and a point-pair practice that Li did not use. A modern description of the vessels follows one or a mixture of these. AcuiQ records which points a study prescribed; a prescription that pairs two confluent points may or may not have been chosen for the vessels, and the entry does not say.