The channel system, counted

The channel system, or meridian system, is the fourteen routes across the body on which classical Chinese medicine places most acupuncture points. Each channel runs in a fixed direction and numbers its points along the way, so that a code such as ST36 names a channel and a position on it.

The fourteen

Twelve channels are paired with organs and run in yin and yang pairs along the limbs. Two more, the Conception and Governing vessels, run up the midline front and back. Between them they carry 361 points. A WHO working group agreed on those 361 in Manila in 1982, and part 1 of the WHO nomenclature, revised in 1991, gives each one a code. Three codes in the table below are this catalogue’s rather than WHO’s, and the WHO column gives the standard form beside each; Reading a point code explains why AcuiQ keeps its own.

The counts differ widely. The Bladder channel carries 67 points and runs the length of the body, down both sides of the spine, where it collects the back-shu points. The Heart and Pericardium channels carry nine each and spend eight of them on the arm: each begins on the trunk, at HT01 in the armpit and PC01 beside the nipple, and runs from there to a fingertip.

Where the twelve come from

The 1991 report of the WHO Scientific Group that proposed the international nomenclature traces the channels to the Huangdi Neijing, the Yellow Emperor’s Inner Canon, and states that both of its parts, the Su Wen and the Ling Shu, describe where the twelve main channels begin and end. Older texts describe fewer. Huang and colleagues, writing in 2017, compare the Neijing with two silk manuscripts excavated in 1973 from Han tomb 3 at Mawangdui, which they date to the late Qin or early Han.

The manuscripts describe eleven vessels, each with a start, an end and a course but no acupoints, and none joined to another. The Neijing, by their comparison, has twelve, each affiliated with an organ and joined end to end in a fixed sequence. It also describes other kinds of pathway beside the twelve: Paulo and Zhang list eight extraordinary vessels, twelve network vessels, twelve channel sinews and a set of 28 vessels.

Ling Shu chapter 10, Jingmai (經脈), names each of the twelve from three parts: an organ, a limb, and one of six yin and yang names. The chapter’s account of the vessels opens on 肺手太陰之脈, the vessel of the lung, hand taiyin. The WHO report keeps that structure in the pinyin name it gives each channel, shǒutàiyīn fèijīng for the Lung, and the classical names in the table above are the limb and yin-yang parts in English. Su Wen chapter 24, Xueqi xingzhi, pairs the six names as exterior and interior, on foot and hand alike: taiyang with shaoyin, shaoyang with jueyin, and yangming with taiyin (on the hand the text names the jueyin partner 心主, the heart master). On the arm that pairs Lung with Large Intestine, Heart with Small Intestine and Pericardium with Triple Burner; on the leg, Spleen with Stomach, Kidney with Bladder and Liver with Gallbladder.

The order of the circuit

The table follows the order of Ling Shu chapter 10, which describes the twelve from lung to liver and has each pass on to the next. The lung vessel runs down the arm to the end of the thumb and sends a branch from behind the wrist to the end of the index finger, where the large intestine vessel begins. The last passage closes the loop: a branch of the liver vessel leaves the liver, crosses the diaphragm and rises to the lung.

Chapter 38, Nishun feishou, gives the direction of each group of three: the hand yin channels run from the organs to the hand, the hand yang from the hand to the head, the foot yang from the head to the foot, and the foot yin from the foot to the abdomen. Huang and colleagues tabulate the same four directions for the Neijing, with the foot yin ending at the thorax rather than the abdomen; the Mawangdui vessels, run from the limbs towards the trunk, except the shoulder vessel and hand taiyin in one of the two texts.

The WHO report numbers each channel’s points along “the agreed course” of that channel, and AcuiQ’s ordinals follow the same course, so the numbering traces the directions in chapter 38. The Lung channel runs from LU01 (Zhongfu) below the collarbone to LU11 (Shaoshang) at the thumbnail, and the Large Intestine channel starts at LI01 (Shangyang) at the index fingernail. A foot yin channel counts upwards, from KD01 (Yongquan) on the sole to KD27 (Shufu) below the collarbone; a foot yang channel counts downwards, from BL01 (Jingming) at the inner corner of the eye to BL67 (Zhiyin) at the little toe. The Liver channel ends the sequence at LV14 (Qimen) below the nipple.

The eight extraordinary vessels

The Conception and Governing vessels also belong to a second group. The WHO report lists eight extra meridians and notes that these two, though counted among the fourteen main ones, are by custom also two of the eight, and the only two of the eight with points of their own. The other six carry no points, so this catalogue has no code for them. The extraordinary vessels covers what the classical texts say about them.

English names and codes

Two-letter codes for every channel date from 1989. Part 1 records that the Manila group in 1982 gave one capital letter to a channel whose Han name has one character, and added a lower-case letter where two clashed: L for lung and Liv for liver, S for stomach and Sp for spleen. It also notes that a code such as H could mean heart in one source and liver (hepar) in another. The Geneva meeting of 1989 replaced these with two capitals for every channel, the codes in the WHO column above. An annex to part 1 lists the codes in use before the standard, among them TB for the triple energizer and LV for the liver, two of the three forms AcuiQ keeps; KD is not among its kidney codes.

The English names differ as well. The standard calls the channel the triple energizer and the posterior midline the governor vessel, where this catalogue says Triple Burner and Governing Vessel. AcuiQ also pads the ordinal to two digits, printing LU01 where the standard prints LU1.

Points outside the channels

The channels are not the whole catalogue. The points AcuiQ indexes outside the fourteen fall into seven groups.

The last two groups are coded on different principles from the extra points. Auricular points map the whole body onto the outer ear, and their codes do not borrow the channel abbreviations. Their prefixes name parts of the ear rather than channels or regions of the body: the helix and its crus, the antihelix and its two crura, the tragus, the antitragus and the notch between them, the scapha, the triangular fossa, the two halves of the concha, the lobe and the back of the ear.

The scalp lines are lines rather than points, needled along their length. Part 2 of the 1991 nomenclature defines all fourteen, MS1 to MS14, by the points each starts from or runs between, almost all of them channel points, and this catalogue carries the same fourteen under the same names and in the same order. The ear has no such anchor: the 1991 nomenclature does not contain it, so the ear’s numbering is the part of the catalogue that agrees least with the codes papers use. Reading a point code covers what happened next.

What the count is good for

The 361 are a short, fixed vocabulary, and most prescriptions in AcuiQ’s index take every point they use from it. That is what makes a corpus of prescriptions countable: the same point, ST36 for one, recurs from paper to paper under the same code. AcuiQ’s method rests on that property.