Heavenly tenth

Also tian-gui.

1. Reproductive viability; that upon which development of the human body, sexual function, and in women the ability to produce offspring depends. Plain Questions (素问 sù wèn, shàng gǔ tiān zhēn lùn) states, [In the male] at the age of two eights [i.e., sixteen] kidney qì is exuberant, heavenly tenth tiān guǐ arrives, essential qì flows forth, yīn and yáng are in harmony, and [he] can beget offspring... At the age of seven eights [i.e., fifty-six] the heavenly tenth is exhausted, essence diminishes, the kidney grows weak, and the body loses its tone; at eight eights, the teeth and hair fall out. [In the female] at the age of two sevens, the heavenly tenth arrives, the controlling (rèn) vessel flows, and the thoroughfare (chōng) vessel fills, the menses come according to their times, and [she] can bear offspring... At seven sevens, the controlling (rèn) vessel empties, the thoroughfare (chōng) vessel weakens, the heavenly tenth is exhausted, the passages of the earth are cut, the body deteriorates, and she can no longer bear children. These statements indicate that the arrival of the heavenly tenth corresponds to the point at which reproductive maturity is reached, and its exhaustion to the point at which reproductive function disappears. They further appear to indicate that the heavenly tenth is a product (material or functional) of the exuberant kidney qì, kidney qi being most clearly understood in this context as the essential qì of the kidney. The term tiān guǐ is composed of guǐ, meaning the tenth heavenly stem (S10) preceded by the tiān, heaven. According to one interpretation, heaven denotes earlier heaven (congenital constitution), whereas guǐ denotes yīn water (as in the combination 壬癸 rén guǐ, yīn and yáng water), by which tiān guǐ would be the yīn water of earlier heaven, i.e., kidney yīn or original yīn. However, this interpretation is difficult to reconcile with the association of tiān guī with kidney qì in the cited passage.

2. Original yīn.

3. Menstruation.

Etymology

Chin 天 tiān, heaven; 癸 guǐ tenth heavenly stem.