Heart governs the tongue

The Magic Pivot (灵枢 líng shū) states, Heart qì flows through to the tongue; when the heart is in harmony, the tongue can distinguish the five flavors. When the heart and spirit are healthy, the tongue can move normally and speech is fluent. When the heart spirit is unclear, as when the heart (or pericardium) is affected by an evil, the tongue becomes sluggish or develops a tremor and speech is impeded. Sufficiency of heart blood is reflected in a fresh vital appearance of the tongue, whereas heart blood vacuity is reflected in a pale dull tongue. In heart yīn vacuity or effulgent heart fire, the tip (or the whole body) of the tongue is red, prickly, or eroded. Stagnation of the heart blood is characterized by a purple tongue with dark blood stasis speckles. For these reasons, it is also said that the tongue is the sprout of the heart and the heart opens at the tongue. Despite the special relationship between the heart and tongue, the condition of all the other organs, particularly the spleen, is reflected in the state of the tongue and its fur.