Qibo answered, "For a woman, her Shenqi (Kidney-Qi) becomes prosperous and her teeth begin to change at the age of seven. At the age of fourteen, Tiangui begins to appear, Renmai (Conception Vessel) and Chongmai (Thoroughfare Vessel) are vigorous in function. Then she begins to have men­struation and is able to conceive a baby. At the age of twenty-one, as Shenqi (Kidney-Qi) is in vigor, the wisdom teeth begin to grow and the her body has fully developed. At the age of twenty-eight, her musculature and bone become strong, her hair grows long enough. Her body has reached the summit of development. At the age of thirty-five, Yangming Channel starts to decline, her face begins to wither and her hair starts to lose. At the age of forty-two, as the three Yang Channels are deficient [in both blood and Qi], her countenance becomes wane and her hair begins to turn white.At the age of forty-nine, as both the Renmai (Conception Vessel) and Chongmai (Thoroughfare Vessel) become deficient and men­struation stops, she becomes physically feeble and is no longer able to conceive a baby. For a man, at the age of eight, his Shenqi (Kidney-Qi) becomes prosperous and his teeth begin to change. At the age of sixteen, as Shenqi (Kidney-Qi) is abundant and Tiangui occurs, he begins to experience spermatic emission. If he has copulated with a woman at this period, he can have a baby. At the age of twenty-four, his Shenqi (Kidney-Qi) is full, his musculature and bone become strong, the wisdom teeth appear and the whole body is fully developed. At the age of thirty-two, his musculature and bones have well developed and are very strong. At the age of forty, as Shenqi (Kidney-Qi) declines, his hair begins to drop and his teeth start to wither. At the age of forty-eight, Yangqi over the upper part of the body collapses, his face starts to wither and his hair begins to turn white. At the age of fifty-six, as Ganqi (Liver-Qi) declines, his musculature becomes inflexible. With the exhaustion of Tiangui and the reduction of Shenqi (Kidney-Qi), his kidney is weakened and his body becomes very weak, his teeth and hair begin to lose. The kidney controls water, it receives and stores Jing (Essence) from Five Zang-Organs and the Six Fu-Organs. Thus only when the Five Zang-Organs and the Six Fu-Organs are vigorous can [the kidney have enough Essence] to discharge. Now the Five Zang-Organs have declined, the bones become weak and the Tiangui is exhausted, his hair turns white and his body becomes clumsy. [As a result, ] he walks with dif­ficulty and is unable to have a baby."