夫痘之为症，与伤寒相似，从表入里，只见一经，形症痘疹从里出表，而五脏之症
皆见，其所以次第传注者，肾心脾肝肺也。一二日出于肾之骨髓，而传心血脉之分，若
血气充足者，则尽传于血脉，而无少留于骨髓，二三日则尽传于胃肌肉，而无少留于血
脉，三四日则尽传于肝筋，而无少留于肌肉，四五日则尽传于皮毛，而无少留于肝
筋，五六日则尽出于疮疹，而无少留于皮毛，如是则七八日脓水渐干，十日十一日则
乃结痂，十二三日则痂落而体光泽矣。若初出于心而少留于骨髓，则浑身壮热，口干闷
乱，则虽出于肌肉，而少留于血脉，则惊掣烦谵，痘不圆肥，若虽出于肝筋，而少留于
肌肉，则发痈毒多在四肢，若虽出于皮毛，而少留于肝筋，则搐搦抽掣，而紫黑潮热，
若虽出于疮疹，而少留于皮毛，则痂迟落而多麻瘢，故痘传四经，而肾无留邪者，吉，
若初热便作腰痛，而见点紫黑者，多死，盖毒瓦斯深伏于肾经，而不能发越耳。
夫痘起于经络，轻者自轻，重者自重，何有轻变重重变轻也？谓之轻变重者，其意
不言夫轻痘之变于重也，盖言人自轻视其痘，则变于重也。更谓之重变轻者，其意亦
不言夫重痘之变于轻也，盖言人能重视其痘，则变于轻也。假如痘毒将发，枭炎蒸
灼，毛孔俱开，正寒暑易受之时也。及其既发，则中表俱虚，尤为饮食易伤，外邪易感
之际也，痘即顺美，倘恃其症轻而风寒不避，饮食不节，房室不成，污秽不避，过服
寒凉，生人不忌，调理失宜，是以风邪外凑，脾胃内伤，变为坏症矣。倘即痘来稠
密，而郑重视之，谨其调理，节其嗜欲，守其禁忌，调其脾胃，是则阴阳得适，气血相
和，逆者难冀其生，险者保其无咎矣。
痘疹这一病症，与伤寒相似，病邪由表入里，仅涉及一经；而痘疹的形态和症状是从体内发出至体表，五脏的症状都会显现出来。其传变的次序是：肾、心、脾、肝、肺。第一二天，痘毒出于肾之骨髓，并传变至心的血脉之分；如果血气充足，则完全传变于血脉，而在骨髓中无丝毫残留；第二三天，则完全传变至胃的肌肉层，而在血脉中无丝毫残留；第三四天，则完全传变至肝的筋脉，而在肌肉中无丝毫残留；第四五天，则完全传变至皮毛，而在肝筋中无丝毫残留；第五六天，则完全出于疮疹，而在皮毛中无丝毫残留。像这样，到第七八天脓水逐渐干燥，第十一天十二天则结痂，第十二三天则痂皮脱落而身体恢复光泽。
如果痘毒初起时出于心而在骨髓中有少许残留，则会出现全身高热、口干、烦闷神乱的症状；即使痘毒已出于肌肉，但在血脉中有少许残留，则会出现惊厥抽搐、烦躁谵语，且痘粒不圆润饱满；如果痘毒虽出于肝筋，但在肌肉中有少许残留，则容易在四肢发生痈肿毒疮；如果痘毒虽出于皮毛，但在肝筋中有少许残留，则会出现抽搐掣动、痘色紫黑及潮热；如果痘毒虽出于疮疹，但在皮毛中有少许残留，则痂皮脱落迟缓且留下较多麻痕疤痕。因此，痘毒传遍四经（心、脾、肝、肺），而肾经无留邪者，为吉兆；如果初起发热时就出现腰痛，且痘点呈紫黑色，多预后不良致死，这是因为毒瓦斯深伏于肾经，而不能透发外越的缘故。
痘毒起源于经络，轻症保持其轻，重症保持其重，怎么会有轻症转重、重症转轻的情况呢？所谓“轻变重”，其意并非指轻症本身的性质转变为重症，而是指人轻视对待痘病，从而导致病情转为严重。所谓“重变轻”，其意也并非指重症本身的性质转变为轻症，而是指人能重视对待痘病，从而使病情转为轻微。假如痘毒将要发作，炎症炽盛灼热，毛孔全部张开，正是寒暑邪气容易侵袭的时候。等到痘毒已经发出，则表里俱虚，更是饮食容易受伤、外邪容易感应的时机。即使痘疹发展顺利美好，倘若倚仗症状轻微而不躲避风寒，饮食不加节制，房事不知禁忌，不避开污秽环境，过度服用寒凉药物，对生人熟物不加忌讳，调理失当，因此风邪从外部凑集，脾胃从内部受损，从而变为坏证。如果痘毒来得稠密，但郑重地重视它，谨慎进行调理，节制嗜欲，遵守禁忌，调和脾胃，这样阴阳得以适宜，气血相互和谐，即使是逆证也难以期望其生存，险证也能保证没有灾祸了。
The manifestation of smallpox (Xiaochuan) is similar to Shanghan (Cold Damage), with the pathogen entering from the exterior into the interior, affecting only one meridian. In contrast, the morphology and symptoms of smallpox emerge from the interior to the exterior, presenting symptoms of all five Zang organs. The sequence of transmission is Kidney, Heart, Spleen, Liver, and Lung. On the first or second day, the eruption originates from the bone marrow of the Kidney and transmits to the blood vessels of the Heart; if Qi and Blood are sufficient, it fully transmits to the blood vessels without any residue in the bone marrow. On the second or third day, it fully transmits to the muscles of the Stomach without any residue in the blood vessels. On the third or fourth day, it fully transmits to the sinews of the Liver without any residue in the muscles. On the fourth or fifth day, it fully transmits to the skin and hair without any residue in the sinews. On the fifth or sixth day, it fully emerges as pustules/rash without any residue on the skin. In this manner, by the seventh or eighth day, pus and fluid gradually dry up; by the tenth or eleventh day, scabs form; by the twelfth or thirteenth day, scabs fall off, and the body regains luster.
If the eruption initially arises from the Heart but leaves slight residue in the bone marrow, there will be high fever throughout the body, dry mouth, restlessness, and confusion. Even if it emerges from the muscles, if slight residue remains in the blood vessels, there will be convulsions, irritability, delirium, and the pustules will not be round and plump. If it emerges from the sinews of the Liver but slight residue remains in the muscles, carbuncles and sores will frequently occur on the four limbs. If it emerges from the skin but slight residue remains in the sinews, there will be spasms and twitching, purple-black discoloration, and tidal fever. If it emerges as pustules but slight residue remains on the skin, the scabs will fall off late and leave many pockmarks. Therefore, if the smallpox transmits through the four meridians (Heart, Spleen, Liver, Lung) and there is no residual pathogen in the Kidney meridian, it is auspicious. However, if lower back pain appears at the onset of fever and the spots are purple-black, death is likely, because the toxic qi is deeply entrenched in the Kidney meridian and cannot vent outward.
Smallpox originates in the meridians; mild cases remain mild, and severe cases remain severe. How can a mild case become severe or a severe case become mild? When we say "mild becomes severe," it does not mean the nature of the mild disease transforms into severity, but rather that people treat the mild disease lightly, causing it to worsen. When we say "severe becomes mild," it does not mean the nature of the severe disease transforms into mildness, but rather that people take the severe disease seriously, causing it to improve. For instance, when the smallpox toxin is about to erupt, inflammation is blazing and burning, and pores are all open, which is precisely the time when cold and heat pathogens are easily invaded. After the eruption has occurred, both the interior and exterior are deficient, making it especially a time when diet easily injures the body and external pathogens are easily contracted. Even if the smallpox develops smoothly and beautifully, if one relies on the mild symptoms and fails to avoid wind and cold, fails to regulate diet, engages in sexual activity improperly, fails to avoid filth, overuses cold-natured medicines, disregards dietary taboos regarding raw or cooked food, and manages care improperly, then wind pathogens will gather externally, and the Spleen and Stomach will be injured internally, resulting in a complicated and adverse condition. Conversely, if the eruption is dense, but one treats it with utmost seriousness, carefully manages care, moderates desires, observes taboos, and harmonizes the Spleen and Stomach, then Yin and Yang will be balanced, and Qi and Blood will be harmonious. Adverse conditions may hardly be expected to survive, but dangerous conditions can be ensured to have no calamity.