How Long Are the Thirty-Seven Channel Passages? The Mirror Classic’s Whole-Body Geometric Ledger

“Kuidu (IV)” returns to a principle introduced as early as the fourth chapter of the work:

Human beings differ in height and length; use the divisions of bone measure and compare them as chi.

The text then begins listing channel-passage lengths one group at a time: the six hand yang together measure three zhang; the six hand yin, two zhang one chi; the six foot yang, four zhang eight chi; the six foot yin, three zhang nine chi. It then adds Yinwei, Yangwei, Yinqiao, Yangqiao, the left and right Chong, Ren, Du, and Dai vessels.

This is not merely a list of channel names but a geometric ledger of the whole body.

Every length is converted into a number of breaths

Because the text has already established that “in one breath of a normal person qi travels six cun,” distance can be converted into the number of breaths required.

For example, if the six hand yang channels together measure three zhang, the text says normal-person qi requires fifty-plus breaths; for the six foot yang channels at four zhang eight chi, it gives eighty-plus breaths.

Once again, “channel length” and “qi-movement time” are bound together.

The extraordinary vessels receive geometric roles of warp, weft, and pivot

The text says:

Ren and Du are the warp; Wei and Dai are the weft; Chong and Qiao are the pivots.

This is more than a list. It assigns directional structure to the whole body: Ren and Du provide a longitudinal central axis; Wei and Dai create transverse and binding structure; Chong and Qiao undertake pivoting and vertical communication.

The passage later calls “Chong, Ren, Du, Qiao, Wei, and Dai the root of the spirit mechanism.”

What is the total length of the thirty-seven vessels?

The text concludes:

The thirty-seven vessels of the human channels and vessels—upper and lower, left and right, front and back—are all channel passages that circuit the body. Altogether they total twenty-two zhang, three chi, and six cun.

This total exactly reconnects with the early statement that Nourishing and Defensive qi travel one complete circuit of the body over “twenty-two zhang, three chi, and six cun.”

The numerical closure matters: early in the work, one breath of six cun was scaled upward to whole-body circulation; here, individual channel-passage lengths are added upward to the same total.

The eighth series completes the whole-body scale here

By this point, the Mirror Classic has established a time scale, bone-measure scale, Hou positions, She positions, tonal degree, lü degree, and a total length of whole-body channel passages.

The final series then suddenly reminds us that even such an elaborate ruler cannot be imposed identically on everyone. Different people may have different normal breath-pulse structures.