Why Can the Pulse Be Fast or Slow, Long or Short? The Meaning of One Cun Five Fen per Movement

The earlier six-cun measure described qi movement across a complete respiratory cycle. The Mirror Classic of Bian Que now reduces the scale one step further and asks: how much qi movement should correspond to one pulse movement itself?

The text says:

In the breath of a normal person, one pulse movement carries qi one cun and five fen. If one movement carries qi less than fourteen fen, the breath is rapid and short; if it exceeds sixteen fen, the breath is gradual and long. The divisions that combine into one breath constitute the lü of the pulse.

Here, “fast/slow” and “long/short” are formally tied together.

One cun five fen per movement is the differential scale of the six-cun model

During one exhalation the pulse moves twice while qi travels three cun, so each movement corresponds on average to one cun five fen. This matches the earlier proportion exactly.

One cun five fen per movement can therefore be treated as the basic pulse-event reference for a normal person.

If the distance per movement is smaller, the text calls it “rapid breath and short.” If larger, it calls it “gradual breath and long.” This is noteworthy: “rapid” and “long” are not treated as two unrelated pulse qualities, but described through a shared spacetime ratio.

Fast and slow are not merely beats per minute

Today, a “fast pulse” usually first suggests heart rate per minute. But the Mirror Classic’s “rapid breath and short” also includes a spatial concept: within a unit pulse event, the proportional distance traveled by qi is shorter.

Conversely, “gradual breath and long” is not only slower frequency; the ratio between pulse events and qi-travel distance has shifted in another direction.

The book may therefore be concerned not with a single frequency variable, but with the whole relation of a pulse event to respiratory phase and spatial division.

Lü is therefore more than pitch

The final sentence says: “The divisions that combine into one breath constitute the lü of the pulse.”

This is the real preparation for the Twelve Lü.

If lü meant only musical pitch, it would be hard to understand why the text first discusses fourteen, fifteen, and sixteen fen per movement. But if lü describes the proportional regulation of pulse and breath movement, the sequence makes sense.

Later, different lü are assigned different divisions, including Huangzhong at sixty fen, Dalü at fifty-seven and a half fen, and Ruibin at fifty-three fen. All of them must be read against this breath/movement/division baseline.

This is the first genuine concept of deviation

Once roughly fifteen fen per movement is established as the normal reference, the text can speak of falling short or exceeding it. Once six cun per breath is established, one can say a channel’s lü is shorter than Huangzhong. Once normal phase is defined, one can discuss being in position or out of position.

In other words, diagnosis begins not with the disease name, but with deviation from a baseline.

This idea continues directly into Qiheng: heng is the measurable normal, and qi is deviation from that normal.

The next article closes the first series by asking why the Mirror Classic regards tone, breath, and pulse as different projections of the same qi-transformational process.