舌诊

The tongue is called "the sprout of the Heart" and "the exterior reflector of the Spleen," and through its meridian connections it is linked to nearly every internal organ. Changes in the qi, blood, fluids, and organs are therefore mirrored on the tongue with unusual fidelity. Tongue inspection has very ancient roots, but it became a distinct subdiscipline only with the Yuan dynasty work the Golden Mirror of Cold Damage Tongue Inspection (《敖氏傷寒金鏡錄》), and developed rapidly through the Ming and Qing.

Two aspects of the tongue are evaluated in parallel. The tongue body (舌质, shé zhì) — the underlying flesh — primarily reflects the state of the zang-fu organs and the qi and blood. The tongue coating (舌苔, shé tāi) — the layer that overlies the body — primarily reflects the strength of stomach qi and the nature and depth of any pathogen present.

A normal tongue body is pale red and moist, of medium size and shape. Common abnormalities and their meanings:

Pale tongue: lighter in color than normal. Indicates qi and blood vacuity or yang vacuity with cold.

Red tongue: darker in red than normal. Indicates a heat pattern. A bright red tongue indicates excess heat; a deep crimson (绛, jiàng) tongue indicates that heat has entered the nutritive (营, yíng) and blood levels, a serious development in febrile disease.

Purple tongue: the whole tongue or patches of it appear purple. A dark purple or stasis-spotted tongue indicates blood stasis; a bluish-purple tongue indicates congealing cold or yang vacuity.

Enlarged tongue: the tongue is bigger than the patient's mouth comfortably accommodates, often with tooth-marks at the edges from pressing against the teeth. Indicates Spleen vacuity with damp accumulation or phlegm-fluid retention.

Thin tongue: a notably small, thin tongue indicates depletion of qi, blood, or yin fluids.

Cracked tongue: visible furrows on the tongue surface. Indicates yin vacuity or blood vacuity, depending on the pattern of cracks.

A normal tongue coating is thin, white, and moist. Common abnormalities:

White coating: a thin white coating may be normal or may indicate an exterior or cold pattern. A thick white coating indicates accumulation of damp turbidity in the interior.

Yellow coating: indicates a heat pattern. Pale yellow indicates mild heat; deep yellow indicates strong heat; scorched yellow indicates extreme heat that has begun to damage fluids.

Gray or black coating: indicates either severe interior heat or severe cold-damp, depending on the moistness of the tongue and the color of the body beneath it.

Thick coating: a notably thickened, often greasy coating indicates dampness, phlegm, or food accumulation.

Thin coating: a coating of normal thinness usually indicates that the upright qi is not yet damaged and the illness is not severe.

Greasy coating (腻, nì): the coating appears sticky, oily, or curdled. Indicates damp turbidity, phlegm, or food stagnation.

Dry coating: indicates insufficient body fluids — either depleted or scorched off by heat.

Peeled coating: patches of the coating have flaked away, leaving "map-like" bare areas. Indicates damaged stomach qi or depleted stomach yin.