褚尚书曰∶饮食五味，养髓、骨、肉、血、肌肤、毛发。男子为阳，阳中必有阴，阴中
之数八，故一八而阳精升，二八而阳精溢；女子为阴，阴中必有阳，阳中之数七，故一七而
阴血升，二七而阴血溢。阳精阴血，皆饮食五味之秀实也（盛衰之道，在七损八益中）。方其升也，智虑开明，齿牙更
始
，发黄者黑，筋弱者强；暨其溢也，凡充身肢体手足耳目之余，虽针芥之沥，无有不下，凡
子形肖父母者，以其精血尝于父母之身，无所不沥也。是以父一肢废，则子一肢不肖其父；
母一目亏，则子一目不肖其母。精未通，而御女以通其精，则五体有不满之处，异日有难状
之疾；阴已痿而思色，以降其精，则精不出内，故小便道涩而为淋。精已耗而复竭之，则大
小便道牵疼，愈疼则愈欲大小便，愈便则愈疼。女人天癸既至，逾十年无男子合，则不调，
未逾十年，思男子合，亦不调；不调则旧血不出，新血误行，或渍而入骨，或变而之肿，或
虽合而难子。合男子多，则沥枯虚人；产乳众，则血枯杀人，观其精血思过半矣。（血竭者，淫白液；精竭者，必血来。
一以气不及化血，一以血不及化精，二者病则一般，其为害又不止于此）
褚尚书曰∶男女之合，二精皆畅，阴血先至，阳精后冲，血开裹精，精入为骨，而男形
成矣；阳精先入，阴血后参，精开裹血，血入为骨，而女形成矣。阳气聚面，故男子面重，
溺死者必伏；阴气聚背，故女子背重，溺死者必仰。走兽溺死，仰伏皆然。阴阳均至，非男
非女之身，精血散分，骈胎品胎之兆∶父少母老，产女必羸，母壮父衰，生男必弱。古之良
工，首察乎此，气受偏瘁，与之补之。补羸女则养血壮脾，补弱男则壮脾节色。羸女宜及时
而嫁，弱男宜待壮而婚，此疾外所务之本，不可不察也。
丹溪曰∶成胎以精血之后先分男女者，褚澄之论也，愚窃惑焉！后阅东垣方有曰，经水
断后一二日，血海始净，精胜其血，感者成男；四五日后，血脉已旺，精不胜血，感者成女
。此论亦为未莹，何以言之？《易》曰∶干道成男，坤道成女。夫乾坤，阴阳之性情也，左
右，阴阳之道路也，男女，阴阳之仪象也。父精母血，因感而会。精之泄，阳之施也；血能
摄之，阴之化也。精成其骨，此万物资始于干元也；血成其胞，此万物资生于坤元也。阴阳
交媾，胎孕乃凝。胎之所居，名曰子宫，一系在下，上有两歧，一达于左，一达于右。精胜
其血，及刚日阳时感者，则阳为之主，受气于左子宫，而男形成；精不胜血，及柔日阴时感
者，则阴为之主，受气于右子宫，而女形成。或曰∶分男分女吾知之矣，其有双胎者，将何
如？曰∶精气有余，歧而分之，血因分而摄之故也。故夫男女同孕者，刚日阴时感，柔日阳
时感，则阴阳混杂，不属左，不属右，受气于两歧之间者也。亦有三胎四胎五胎六胎者，犹
是而已。或曰，其有男不可为父，女不可为母，与男女之兼形者，又若何而分之耶？予曰，
男不可为父，得阳气之亏者也，女不可为母，得阴气之塞者也；兼形者，由阴为驳气所乘，
而为状不一。以女兼男形者有二∶一则遇男为妻，遇女为夫；一则可妻而不可夫；又有下为
女体，上具男之全角，此又驳之者也。或曰∶驳气所乘，独见于阴，而所乘之形，又若是之
不同耶？予曰，阴体虚，驳气易于乘也。驳气所乘，阴阳相混，无所为主，不可属左，不可
属右，受气于两岐之间，随所得驳气之轻重而成形，故所兼之形，有不可得而同也。
褚尚书说：饮食的五味，能够滋养髓、骨、肉、血、肌肤和毛发。男子属阳，阳中必含有阴，阴中的数理是八，所以男子八岁时阳气升发，十六岁时阳精满溢；女子属阴，阴中必含有阳，阳中的数理是七，所以女子七岁时阴血升发，十四岁时阴血满溢。阳精和阴血，都是饮食五味所化生的精华（盛衰的规律，在于“七损八益”之中）。当精气血气升发之时，人的智虑开明，牙齿更换生长，头发由黄变黑，筋骨变得强健；到了精气血气满溢之时，凡是充盈全身肢体手足耳目等余部，即使是像针尖芥子那样微小的点滴，没有不向下灌注的。胎儿形貌像父母，是因为父母的精血曾在父母身上流淌，无处不到。因此，父亲如果有一只肢体残疾，那么儿子就有一只肢体不像父亲；母亲如果有一只眼睛残缺，那么儿子就有一只眼睛不像母亲。
在肾精尚未通调时，就与女子行房以强行泄精，那么五脏形体就会有不完备的地方，日后会有难以名状的疾病；当阴器已经痿软却仍思慕女色，以致泄精，那么精液不能排出而在体内郁结，导致小便道涩滞而成为淋证。精液已经耗损却又再次竭尽，那么大、小便道会牵引疼痛，越疼痛就越想大小便，越大小便就越疼痛。女子天癸（月经）已经来潮，超过十年没有与男子交合，则月经不调；未满十年，思念男子交合，也月经不调；月经不调则旧血排不出，新血误行，有的渗入骨骼，有的变成肿胀，或者虽然交合但难以受孕。与男子交合过多，则精液枯竭使人体虚弱；生育哺乳众多，则血液枯竭危及生命，观察精血的盛衰，道理已过半了。（血枯竭者，表现为白带异常；精枯竭者，必然出现血崩。一种是因为气不足无法化生血，一种是因为血不足无法化生精，这两种病症状一般相同，其危害还不止于此）
褚尚书说：男女交合，双方的精气都通畅，如果是阴血先至，阳精后冲，血液张开包裹住精液，精液进入化为骨，男胎就形成了；如果是阳精先进入，阴血随后参合，精液张开包裹住血液，血液进入化为骨，女胎就形成了。阳气聚于面部，所以男子面部较重，溺水死亡的人必定俯卧；阴气聚于背部，所以女子背部较重，溺水死亡的人必定仰卧。走兽溺水死亡，无论俯卧还是仰卧都有可能。阴阳之气均等到达，形成非男非女的身体，精血分散分布，这是双胎或异卵多胞胎的征兆：父亲年轻母亲年老，生下的女儿一定瘦弱；母亲强壮父亲衰弱，生下的儿子一定弱小。古代高明的医生，首先考察这一点，如果气受偏颇损伤，就给予补益。补益瘦弱的女子要养血壮脾，补益虚弱的男子要健脾节制房事。瘦弱的女子适宜及时出嫁，虚弱的男子适宜等到身体强壮后再结婚，这是治疗疾病之外应当务求的根本，不可不仔细考察。
朱丹溪说：认为成胎时精血到来的先后决定了胎儿性别的说法，是褚澄的理论，我私下对此感到困惑！后来阅读李东垣的方论中提到，月经干净后一两天，血海刚刚洁净，精胜过了血，受孕则成男孩；四五天后，血脉已经旺盛，精胜不过血，受孕则成女孩。这个论述也不够透彻，为什么这么说呢？《易经》说：乾道成就男性，坤道成就女性。乾坤，是阴阳的性情；左右，是阴阳的道路；男女，是阴阳的仪象。父亲的精和母亲的血，因感应而结合。精液的排泄，是阳气的施予；血液能摄持它，是阴气的化育。精形成骨，这是万物资始于乾元；血形成胞，这是万物资生于坤元。阴阳交媾，胎孕才凝结。胎居住的地方，名叫子宫，有一条系带在下端，上面分为两支，一支通达左边，一支通达右边。精胜过了血，以及在刚日阳时受孕的，则由阳为主，在左子宫受气，男胎就形成了；精胜不过血，以及在柔日阴时受孕的，则由阴为主，在右子宫受气，女胎就形成了。有人问：分男女我知道是怎么回事了，那如果有双胞胎，又该怎么办呢？回答说：精气有余，分流而分配，血液随之分别摄持的缘故。所以同孕男女的情况，是在刚日阴时受孕，或柔日阳时受孕，导致阴阳混杂，不属于左，也不属于右，而是在两歧之间受气形成的。也有三胎、四胎、五胎、六胎的，也是同样的道理。有人问：如果有男的不宜做父亲，女的不宜做母亲，以及男女兼形的人，又怎么区分呢？我说：男的不宜做父亲，是得到了亏虚的阳气；女的不宜做母亲，是得到了闭塞的阴气；兼形的人，是由于阴体被驳杂之气所乘，因而形状不一。以女性兼有男性形态的有两种：一种是遇到男人可以做妻子，遇到女人可以做丈夫；一种是可做妻子但不能做丈夫；还有下身是女性体态，上身具备男性的全部特征，这又是驳杂之气的表现。有人问：驳杂之气所乘，唯独见于阴体，而所呈现的形状，又是如此不同吗？我说：阴体虚弱，驳杂之气容易乘虚而入。驳杂之气所乘，阴阳相混，没有主导，既不属于左，也不属于右，在两歧之间受气，随着所得驳杂之气的轻重而形成不同的形态，所以兼有的形状，不可能完全相同。
Shu Shangshu (Minister Shu) said: The five flavors of food and drink nourish the marrow, bones, flesh, blood, skin, hair, and nails. Men belong to Yang, and within Yang there must be Yin; the number associated with Yin is eight. Thus, at age eight, the Yang essence rises; at age sixteen, the Yang essence overflows. Women belong to Yin, and within Yin there must be Yang; the number associated with Yang is seven. Thus, at age seven, the Yin blood rises; at age fourteen, the Yin blood overflows. Both Yang essence and Yin blood are the refined essences derived from the five flavors of food and drink (The principles of decline and increase lie within the "Seven Damages and Eight Benefits"). When these energies rise, one's mental faculties become clear, teeth are replaced, yellow hair turns black, and weak sinews and tendons become strong. When they overflow, every part of the body—limbs, hands, feet, ears, eyes, and beyond—is filled. Even minute drops, like those from a needle or mustard seed, penetrate everywhere. A child resembles their parents because the parental essence and blood have permeated the parents' bodies entirely. Therefore, if a father has a disabled limb, the son will have a limb that does not resemble the father's; if a mother has a missing eye, the son will have an eye that does not resemble the mother's.
If sexual intercourse is practiced before the Jing (Essence) is fully developed, forcing its release, the five organs and physical forms will have deficiencies, leading to difficult-to-describe illnesses later in life. If one engages in sexual desire when the Yin organ is already flaccid, causing the Jing to be expelled, the Jing remains inside without exiting, leading to a涩 (astringent/stagnant) sensation in the urinary pathway, resulting in Lin syndrome (dysuria). If the Jing is exhausted and then further depleted, it causes pain in the pathways of urination and defecation; the more painful it becomes, the more one feels the urge to urinate or defecate, which in turn increases the pain.
When a woman's Tian Gui (Menstruation) arrives, if she has no sexual intercourse with men for over ten years, her cycle will become irregular. If she desires intercourse with men before ten years have passed since menarche, her cycle will also become irregular. Irregularity means old blood fails to exit, while new blood flows erratically; it may seep into the bones or transform into swelling. Even if intercourse occurs, conception may be difficult. Frequent intercourse with men depletes Jing, weakening the person; frequent childbirth and lactation deplete Blood, endangering life. Observing the state of Jing and Blood reveals half the truth. (When Blood is exhausted, white discharge appears; when Jing is exhausted, hemorrhage occurs. One case arises from Qi failing to transform into Blood; the other from Blood failing to transform into Jing. Both present similarly but their harms extend beyond this.)
Shu Shangshu said: In the union of man and woman, if both essences are smooth, and Yin Blood arrives first while Yang Essence follows, the Blood opens to envelop the Essence. The Essence enters and transforms into bone, forming a male fetus. If Yang Essence enters first and Yin Blood follows, the Essence opens to envelop the Blood. The Blood enters and transforms into bone, forming a female fetus. Yang Qi gathers in the face, so men have heavier faces; drowning men typically float prone. Yin Qi gathers on the back, so women have heavier backs; drowning women typically float supine. For quadrupeds drowning, both positions occur. If Yin and Yang arrive equally, a non-male/non-female body may form. If Jing and Blood are scattered, it indicates twins or multiple fetuses. If the father is young and the mother old, the daughter born will likely be frail. If the mother is robust and the father weak, the son born will likely be weak. Ancient skilled physicians examined this first. If Qi is unevenly damaged, they provide tonification. To tonify frail women, one nourishes Blood and strengthens the Spleen. To tonify weak men, one strengthens the Spleen and regulates sexual activity. Frail women should marry promptly; weak men should wait until they are robust. This is the fundamental principle outside of treating disease, which must not be overlooked.
Zhu Danxi said: The theory that the sequence of Jing and Blood determines the sex of the fetus is attributed to Chu Cheng. I have privately doubted it! Later, I read Li Dongyuan's treatise stating: One or two days after menstruation ends, the Sea of Blood is clean, and Jing surpasses Blood; conception results in a male. Four or five days later, the Blood vessels are vigorous, and Jing cannot surpass Blood; conception results in a female. This argument is also not sufficiently clear. Why? The *I Ching* (Book of Changes) states: "The Way of Qian creates Man, the Way of Kun creates Woman." Qian and Kun represent the nature of Yin and Yang; Left and Right represent the paths of Yin and Yang; Male and Female represent the manifestations of Yin and Yang. Father's Jing and Mother's Blood combine through mutual influence. The emission of Jing is the action of Yang; the retention of Blood by Jing is the transformation of Yin. Jing forms the bone, representing the beginning of all things from Qianyuan (Primordial Heaven); Blood forms the uterus/womb, representing the nurturing of all things from Kunyuan (Primordial Earth). Through the coupling of Yin and Yang, pregnancy condenses. The residence of the fetus is called the Zi Gong (Uterus), which has a single root below and bifurcates above, reaching left and right. If Jing surpasses Blood, and conception occurs on a Yang day/hour, Yang dominates, Qi is received in the Left Uterus, and the male form is created. If Jing does not surpass Blood, and conception occurs on a Yin day/hour, Yin dominates, Qi is received in the Right Uterus, and the female form is created.
Someone asked: I understand how sexes are distinguished, but what about twins? I replied: When Jing Qi is abundant, it divides, and Blood captures each portion separately. Thus, pregnancies containing both male and female fetuses occur when conception happens on a Yang day during a Yin hour, or a Yin day during a Yang hour, causing Yin and Yang to mix. They do not belong solely to the left or right, but receive Qi between the bifurcation. There can also be triplets, quadruplets, etc., following the same logic. Someone asked: What about males unable to be fathers, females unable to be mothers, or individuals with intersex characteristics? I said: Males unable to be fathers suffer from deficient Yang Qi; females unable to be mothers suffer from obstructed Yin Qi. Intersex conditions arise because the Yin body is invaded by mixed/impure Qi, resulting in varied appearances. There are two types of females with male characteristics: one who acts as a wife to men and a husband to women; another who can be a wife but not a husband. Another type has a female lower body but complete male upper features, caused by mixed Qi. Someone asked: Does mixed Qi invasion only affect the Yin body, yet produce such diverse forms? I said: The Yin body is deficient, making it susceptible to mixed Qi. When mixed Qi invades, Yin and Yang mix without a dominant force, neither belonging to left nor right, receiving Qi between the bifurcation. The resulting form depends on the severity of the mixed Qi, hence the variations in intersex characteristics.