《黄帝内经·灵枢·口问》
岐伯回答说：这是阴气盛而阳气虚，阴气运行快速而阳气受阻、运行缓慢，甚至阴气亢盛而阳气衰微而造成的。
岐伯曰：此阴气盛而阳气虚，阴气疾而阳气徐，阴气盛而阳气绝，故为唏。
Qi Bo answered: "This is caused by vigorous Yin Qi and weak Yang Qi, rapid movement of Yin Qi and sluggish movement of Yang Qi, or even excessive Yin Qi and deficient Yang Qi."