圣济总录∶小儿在母腹中，受其精气而成形。一月血凝，二月成胚胎，三月如桃花，阳神为魂，四月分四肢，阴灵
为魄，五月五行分五脏，六月六律定六腑，七月七精开窍，八月八景俱全，九月气象成，十月百神集备而生也。生后六
十日瞳子成，笑语识人；百日任脉生能反复；一百八十日尻骨成能独坐；二百一十日掌骨成能匍匐；三百日胫骨成能独
倚；三百六十日为一期，骨节成乃能移步而行。夫医之道至难也，治小儿则尤难。盖周岁之间，精神未备，骨格未坚，
形声未正，脉息未全。语不能问其得病之由，脉不能诊其必然之理。故云∶冠壮易明，幼童难治。苟不潜心玩味，何乃
寄幼儿之司
命也。
人皆谓婴儿满十月而生，余究内经理，二百七十日实为定论。盖就中虚计一月，以应十个月之数也。经云∶九九为
上，八八次之，七七又次之。凡人之生，禀二仪之气会合，三才之道各得其九，三九二十七，则二百七十日而生。八八
者，三才各得其八，三八二十四则二百四十日而生。七七者，三才各得其七，三七二十一则二百一十日而生。
其逾十月而生者为大过，其七八月而生者为不及。大过者气血阴之有余；不及者，血气养之不足也。大抵人得中道而生，
阴阳剂合，刚柔兼济；气血相和，百脉相调；心智明通，精神全备；脏腑充实，形体壮健。观其颅囟便可知矣。未周之
儿，颅囟坚合，睛黑神清，口方背浓，骨粗臀满，脐深肚软，茎小卵大，齿细发润，声洪睡稳，此乃受气得全者。如二
三岁，其囟尚大解开，齿发未生，手脚挛缩，膝如鹤节；或五六岁，尚不能行，身体手足瘦瘠者，此皆受气不足故也。
《圣济总录》记载：小儿在母腹中，接受父母的精气而成形。怀孕第一个月血气凝聚，第二个月形成胚胎，第三个月形状像桃花，阳神化为魂；第四个月四肢分化，阴灵化为魄；第五个月五行分别对应五脏，第六个月六律确定六腑，第七个月七精开启孔窍，第八个月八景全部具备，第九个月气象形成，第十个月百神聚集完备后出生。出生后六十天瞳孔成型，能笑能语认识人；一百天任脉生成，能够翻身；一百八十天尻骨长成，能够独自坐立；二百一十天掌骨长成，能够匍匐爬行；三百天胫骨长成，能够独自倚靠站立；三百六十天为一个周期，骨节长成才能迈步行走。医学之道非常艰难，治疗小儿病则尤其困难。因为在一周岁之间，精神尚未完备，骨骼尚未坚固，形体声音尚未端正，脉象气息尚未齐全。孩子不能说话询问得病的原因，医生也不能通过脉诊完全诊断其必然的病理。所以说：成人容易诊断，幼儿难以治疗。如果不潜心钻研玩味医理，怎么能把幼儿的性命寄托给医生呢？
人们都说婴儿满十个月才出生，我研究《内经》理论，认为二百七十天才是确定的结论。大概是因为中间虚计一个月，以应合十个月的数目。经书说：九九为上等，八八为次等，七七又为再次等。大凡人的出生，禀受天地二仪之气会合，三才之道各得其九，三九二十七，就是二百七十天出生。八八的情况，是三才各得其八，三八二十四，就是二百四十天出生。七七的情况，是三才各得其七，三七二十一，就是二百一十天出生。超过十个月出生的属于“大过”，七八个月出生的属于“不及”。“大过”是气血阴气有余；“不及”是血气滋养不足。大致上人得到中和之道而生，阴阳调和，刚柔兼济；气血相和，百脉协调；心智明通，精神全备；脏腑充实，形体壮健。观察其头颅囟门就可以知道了。未满周岁的婴儿，颅囟坚实闭合，眼睛黑亮神态清明，口型方正背部厚实，骨骼粗壮臀部丰满，肚脐深腹部柔软，阴茎小睾丸大，牙齿细头发润泽，声音洪亮睡眠安稳，这是禀受精气完备的表现。如果到了两三岁，囟门还大且未闭合，牙齿头发未长出，手脚挛缩，膝盖像鹤节一样突出；或者五六岁了，还不能行走，身体手足瘦弱干枯的，这都是禀受精气不足的缘故。
*Shengji Zonglu* records: The fetus in the mother's womb takes shape by receiving the essence and qi (vital energy) of its parents. In the first month, blood coagulates; in the second month, the embryo forms; in the third month, it resembles a peach blossom, with the Yang spirit becoming Hun (ethereal soul); in the fourth month, the four limbs differentiate, with the Yin spirit becoming Po (corporeal soul); in the fifth month, the Five Elements correspond to the five Zang organs; in the sixth month, the Six Harmonies determine the six Fu organs; in the seventh month, the Seven Essences open the orifices; in the eighth month, the Eight Sceneries are fully complete; in the ninth month, the phenomena take form; and in the tenth month, the hundred deities gather and prepare for birth. After birth, at sixty days, the pupils form, and the infant can smile, speak, and recognize people; at one hundred days, the Ren Mai (Conception Vessel) generates, enabling turning over; at one hundred eighty days, the sacral bone forms, enabling sitting alone; at two hundred ten days, the palm bones form, enabling crawling; at three hundred days, the tibiae form, enabling standing with support; at three hundred sixty days, completing one cycle, the joints form, enabling walking. The way of medicine is extremely difficult, and treating children is particularly so. This is because within the first year of life, the spirit and mind are not yet complete, the skeletal structure is not yet firm, the physical form and voice are not yet regular, and the pulse and breath are not yet fully developed. The child cannot speak to inquire about the cause of illness, and the pulse cannot be diagnosed to ascertain the inevitable pathology. Thus it is said: Adults are easy to diagnose, while young children are difficult to treat. If one does not devote oneself to studying and pondering medical principles, how can one entrust the lives of infants to their care?
People all say that infants are born after ten full months, but I have investigated the theories of *Neijing* (The Inner Canon), concluding that two hundred seventy days is the definitive standard. This is roughly calculated by accounting for one virtual month to correspond to the number of ten months. The classics state: Nine times nine is the highest grade, eight times eight is the next, and seven times seven is again lower. Generally, human birth results from the convergence of the Qi of Heaven and Earth (Yin-Yang). The Way of the Three Powers (Heaven, Earth, Human) each obtains nine; three nines make twenty-seven, resulting in birth at two hundred seventy days. For eight eights, the Three Powers each obtain eight; three eights make twenty-four, resulting in birth at two hundred forty days. For seven sevens, the Three Powers each obtain seven; three sevens make twenty-one, resulting in birth at two hundred ten days. Birth exceeding ten months is termed "excess" (Da Guo), while birth at seven or eight months is termed "deficiency" (Bu Ji). "Excess" indicates an abundance of Yin Qi in blood and qi; "deficiency" indicates insufficient nourishment of blood and qi. Generally, those born according to the Mean Dao have harmonized Yin and Yang, balanced rigidity and softness, harmonized blood and qi, regulated the hundred vessels, possess clear and penetrating mental faculties, complete spirit and mind, substantial Zang-Fu organs, and robust physical health. This can be observed through the fontanelle. An infant under one year old with a firm and closed cranial fontanelle, black and bright eyes with clear spirit, square mouth and thick back, coarse bones and full buttocks, deep umbilicus and soft abdomen, small penis and large testes, fine teeth and lustrous hair, resonant voice and steady sleep, is one who has received complete essence and qi. Conversely, if at two or three years old the fontanelle remains large and open, teeth and hair have not grown, hands and feet are contracted, knees resemble crane joints; or if at five or six years old the child still cannot walk, and the body and limbs are emaciated and dry, these are all due to insufficient reception of essence and qi.