干父坤母，化生万物，独阳勿克以自生，独阴勿克以自成，而生物之本系焉。是
以男女交媾，亦必二五妙合，而生人之本系焉。（夫二五者，谓阴阳二气及五行也。）此人生之所
自来，而痘之原，亦根于此矣。人皆知其种于淫火之毒，而不知由乎交媾之微，胶稠如
脂者，真元之精也，稀清如水者，淫火之液也。痘原之美恶，乃于此分。故人禀清明之
气，修养之纯，则真元之精浓，而水火相济，淫火之液自少，痘之所发必稀疏而顺
美。人禀淆浊之气，情欲之杂，则真元之精混，而水火相激，淫火之液自倍，痘之所发
必密。比而逆恶，岂俟孕于母腹，而为五辛六疏之物，腥膻煎爆之味，酿成胎毒，传
于男女。结为恶逆之痘乎！李还丹曰∶人有七情，而欲之所动，火之使然。盖欲无火不
动，太过即是淫液也。可见痘之为症，本于阳毒，恶烈而莫御，其母胎之毒，不过发为
疮疥丹瘤而已。更有谓儿含胎血致毒者，尤为不经之论耳。
万物轻清则高，健运则圆，天之象也，气之功也。虽然如以水法丸者，非转运不
停，不能以圆其形；非湿润敛束，不能以遂其圆。故气虚者，果难高耸而致圆晕；血虚
者，亦多燥涩而难流通。然名之曰痘者豆也，因形之类而名之也。又曰∶痘者，头
也，痘毒之标峻，欲其先达头额，以诸阳总会于斯也。又曰∶痘者，投也，投诸时令而
感也。相传谓自西域归染，而痘从此始。又以人身必出一次，故名百岁疮。又类天行疫
疠，故名天花，复以形象而又名之豌豆，更有名之曰斑者，义虽各不同而理则一致也。
然人之生，莫不患痘，有年纪耄耋而不出者，可见其痘可以出，可以不出，嗟嗟！独
不观诸物乎，鹤不发顶，则不能以宏其声，蚕不三眠，则不能以成其绪，蟹不脱壳，则
不能以大其腔，虎不转爪，则不能以奋其威，人之出痘亦犹是也。间有枭毒原少，痘
暴稀鲜，乍出数颗不自知觉，或偶患疮疥，杂出其中，故不晓其为痘耳。若据其可以有
可以无之说，是不求夫人身之原也。
乾为天父，坤为地母，化生万物。纯阳之气不能独自生成，纯阴之气也不能独自成就，万物的根本便在于此。因此，男女交合，也必须是阴阳二气与五行精微结合，才能形成人类的根本。（所谓“二五”，指的是阴阳二气和五行。）这是人类生命的来源，而天花的根源，也是根植于此。人们都知道天花是由淫火之毒引起的，却不知道它源于交合时的细微之处：胶稠如脂的是真元之精，稀清如水的是淫火之液。天花原发的美恶，就在此处区分。所以，人如果禀受清明之气，修养纯正，那么真元之精就会浓稠，水火相互济助，淫火之液自然减少，所发的痘疹必然稀疏且顺美。人如果禀受混浊之气，情欲杂乱，那么真元之精就会混杂，水火相互激荡，淫火之液自然加倍，所发的痘疹必然密集而且逆乱凶恶。难道一定要等到在母腹中孕育时，因为吃了五辛六疏之物、腥膻煎爆的味道，酿成胎毒，传给男女，结为恶逆的痘疹吗！李还丹说：人有七情，而欲望的发动，是火的作用。大概欲望没有火就不会动，太过就是淫液了。由此可见，天花这种病症，本于阳毒，性质恶劣猛烈而无法抵御，其母体中的胎毒，不过表现为疮疥、丹瘤等而已。更有说法认为婴儿含咽胎血导致中毒，这更是荒诞不经的言论。
万物轻清则向上，健运则呈圆形，这是天的形象，是气的功能。虽然如此，但像用水和泥做丸子，如果不是运转不停，就不能使其形状圆满；如果不是湿润收敛束缚，就不能使其成为圆形。所以气虚的人，果然难以高耸并形成圆晕；血虚的人，也多因燥涩而难以流通。然而命名为“痘”是因为它像豆子，是根据形状相似来命名的。又说：“痘”通“头”，指痘毒的标象严峻，希望它先到达头额，因为诸阳经总会聚于此。又说：“痘”通“投”，指投合时令之气而感染。相传说是从西域归来时感染的，天花从此开始。又因为人身必出一次，所以名叫百岁疮。又类似天行疫疠，所以名叫天花，再根据形象又名叫豌豆，更有名叫斑的，含义虽然各不相同，但道理是一致的。然而人生下来，无不患痘，有年纪老迈而不出的，可见痘是可以出，也可以不出。唉！难道不看看其他事物吗？鹤如果不发顶（换羽），就不能使声音宏大；蚕如果不三次眠伏，就不能结成丝绪；蟹如果不脱壳，就不能扩大胸腔；虎如果不转爪，就不能振奋威风。人出痘也是如此。间或有枭毒原少，痘暴稀疏鲜亮，刚出几颗自己没察觉，或者偶然患疮疥，夹杂在其中，所以不知道那是痘罢了。如果依据它可以有也可以无的说法，这就是不探求人体生命本源的做法。
Qian (Heaven) is the father, Kun (Earth) is the mother, giving birth to all things. Pure Yang cannot generate by itself, and pure Yin cannot complete by itself; the root of generating life lies in their interaction. Therefore, when man and woman unite, it must be the subtle combination of Yin-Yang Qi and the Five Elements that forms the basis of human life. ("Er Wu" refers to Yin-Yang Qi and the Five Elements.) This is the origin of human life, and the origin of smallpox is also rooted here. People know that smallpox originates from the toxin of excessive sexual fire, but do not realize its subtle source in conception: the essence that is thick and sticky like fat is the True Yuan Essence, while the fluid that is thin and clear like water is the fluid of excessive sexual fire. The beauty or ugliness of the smallpox origin is distinguished here. Thus, if a person inherits clear and bright Qi and cultivates purity, the True Yuan Essence will be dense, Water and Fire will assist each other, and the fluid of excessive sexual fire will naturally decrease; the resulting smallpox will surely be sparse and smooth/beautiful. If a person inherits turbid Qi and has mixed desires, the True Yuan Essence will be confused, Water and Fire will clash, and the fluid of excessive sexual fire will double; the resulting smallpox will surely be dense and adverse/evil. Must it wait until gestation in the womb, where eating pungent spices and rough foods, or greasy and fried flavors, brews fetal toxin transmitted to the couple, forming evil and adverse smallpox? Li Huan Dan said: "Humans have Seven Emotions, and the movement of desire is caused by Fire. Desire does not move without Fire; excess constitutes the fluid of excessive sexual fire." It can be seen that smallpox as a syndrome is based on Yang Toxin, which is fierce and uncontrollable; the fetal toxin in the mother is merely manifested as sores, carbuncles, erysipelas, or tumors. Furthermore, the claim that infants swallowing amniotic blood causes toxicity is an absurd theory.
All things are light and clear, thus rising high; they move vigorously and form circles, representing the image of Heaven and the function of Qi. Nevertheless, just as making pills with water requires continuous rotation to achieve roundness, and moisture to bind them into shape, so too, those with Qi deficiency find it difficult to rise high and form round halos; those with Blood deficiency often suffer from dryness and obstruction, making circulation difficult. However, it is named "Dou" (Smallpox/Pox) because it resembles beans, named after its shape. It is also said: "Dou" sounds like "Tou" (Head), indicating that the severe manifestation of the pox toxin wishes to reach the head first, as all Yang meridians converge there. It is also said: "Dou" sounds like "Tou" (Cast/Throw), meaning contracting the infection by casting oneself into the seasonal climates. Legend says it was contracted upon returning from the Western Regions, marking the beginning of smallpox. Since every person experiences it once, it is called "Hundred-Year Sore". Similar to epidemic fevers, it is called "Heavenly Flowers"; based on its appearance, it is also called "Pea"; some call it "Ban" (Macules/Rashes). Although the meanings differ, the principles are consistent. Yet, no one is born without the potential for smallpox; some live to old age without manifesting it, showing that smallpox can manifest or not. Alas! Do we not observe other creatures? If the crane does not shed its crown feathers, its voice cannot be loud; if the silkworm does not sleep three times, it cannot spin silk; if the crab does not molt its shell, its cavity cannot expand; if the tiger does not sharpen its claws, it cannot display its majesty. Human smallpox is similar. Occasionally, those with little inherent toxic poison may have very sparse and fresh eruptions, appearing only a few spots unnoticed, or mixing with accidental sores/rashes, leading people to mistake them for something else. To rely on the argument that it can exist or not exist is to fail to seek the origin of human life.