天地者，形之大也；阴阳者，气之大也。性形与气相资而立，未始偏废。男女媾精，万
物化生，天地阴阳之形气寓焉。语七八之数，七，少阳也；八，少阴也，相感而流通。故女子
二七天癸至，男子二八精气盛，则阴阳交合而兆始故也。语九十之数，九，老阳也；十，老
阴也 相包而赋形。故阴穷于九，女能方之，则以阴阳相生而成终故也。元气孕毓，皆始于子。
自子推之，男左旋，积岁三十而至巳；女右旋，积岁二十而至巳。巳为正阳，阴实从之。自
巳怀任，男左旋十月而生于寅；女右旋十月而生于申。申为三阴，寅为三阳，而生育之时着矣。
其禀赋也，体有刚柔，脉有强弱，气有多寡，血有盛衰，皆一定而不可易也。以至分野异域，
则所产有多寡之宜。是故荆扬薄壤多女，雍冀浓壤多男。吉事有祥，则所梦各应其类∶熊罴为
男之祥，蛇虺为女之兆，是皆理之可推者也。至于胎化之法，有所谓转女为男者，亦皆理之
自然。如食牡鸡，取阳精之存于天者；带雄黄，取阳精之存于地者；操弓矢，藉斧斤，取刚物
之见于人事者。气类潜通，造化密移，必于三月形兆之先。盖方仪则未具，形气藉母神而变化，
阳可以阴，而动静之所以相感也。观夫螟蛉之化，又可知矣。物类且然，况于人乎？
Heaven and Earth are the greatest of forms; Yin and Yang are the greatest of Qi (vital energy). Nature, form, and Qi rely on each other to establish existence, never neglecting one for the other. When male and female unite their essence, myriad things are transformed; the form and Qi of Heaven and Yin and Yang are contained within this process. Regarding the numbers seven and eight: seven belongs to Shaoyang (Lesser Yang); eight belongs to Shaoyin (Lesser Yin). They interact and circulate. Thus, when girls reach fourteen years of age, Tian Gui (menstrual fluid/reproductive capacity) arrives; when boys reach sixteen years of age, Jing Qi (essence and Qi) becomes abundant. This is the initial cause of Yin-Yang union and conception. Regarding the numbers nine and ten: nine represents Laoyang (Old Yang); ten represents Laoyin (Old Yin). They envelop each other to endow form. Therefore, Yin reaches its limit at nine; if women can align with this, it is through the mutual generation of Yin and Yang that life concludes. The gestation of Yuan Qi (Original Qi) begins at Zi (the first earthly branch/position).推算 from Zi: males rotate leftward, accumulating thirty years to reach Si; females rotate rightward, accumulating twenty years to reach Si. Si represents Zhengyang (True Yang), and Yin actually follows it. Conception begins at Si; males rotate leftward for ten months and are born at Yin; females rotate rightward for ten months and are born at Shen. Shen represents Sanyin (Three Yin), and Yin represents Sanyang (Three Yang), thus revealing the timing of birth. In terms of innate endowment, the body has rigidity or softness, the pulse has strength or weakness, Qi has abundance or scarcity, and Blood has excess or deficiency. These are fixed and unchangeable. As for different geographical regions, the proportion of births varies accordingly. Therefore, in Jingzhou and Yangzhou where the soil is thin, more girls are born; in Yongzhou and Jizhou where the soil is rich, more boys are born. Auspicious events have omens; dreams correspond to their respective categories: dreaming of bears and tigers is an omen for a boy; dreaming of snakes and vipers is an omen for a girl. These are principles that can be deduced. Regarding methods of fetal transformation, there is the so-called "turning a female fetus into a male," which is also natural law. For example, eating rooster meat takes the Yang essence existing in heaven; wearing Realgar takes the Yang essence existing in earth; handling bows and arrows, relying on axes and knives, takes the rigid objects seen in human affairs. Qi of similar categories secretly communicates, and Creation shifts subtly, necessarily before the third month when the fetal form is established. At this stage, the physical structure is not yet complete; form and Qi change by relying on the mother's spiritual mechanism. Yang can transform into Yin, which is why movement and stillness interact. Observing the transformation of silk moths (Mingling) into other insects, we can understand this. If it is so for other species, how much more so for humans?