人身之气血。与天地同流。人身之经络。与昼夜同度。苟或六淫之感。七情之伤。饮食不时。房劳不节。致
使阴阳乖错。荣卫蕴结而成痈者。总不出于三因。故以三因首例
运气痈疽有四。
一曰、火热助心为疮疡。经曰。少阴所至为疡疹。又云。少阴司天。热气下临。肺气上从。甚则疮疡。又云。少
阴司天之政。补之气。寒乃始。阳气郁。炎暑将起。中外疮疡。又云。少阳所至为疮疡。又云。少阳司天之政。
风热参布。太阴横流。寒乃时至。民病寒中。外发疮疡。初之气。候乃太温。其病肤腠中疮。二之气。火反郁。
其病热郁于上。疮发于中。三之气。炎暑至。民病脓疮。又云。太阳司天之政。初之气。气乃太温。肌腠疮疡。
此皆常化。病之浅也。又云。少阴司天。热淫所胜。甚则疮疡。又云。少阴司天。客胜。甚则疮疡。又云。少阴之
复。病 疹痈疽痤痔。又云。火太过曰赫义。其病疮疽血流。又云。火郁之发。民病疮疡痈肿。此是邪变。病
之甚也。
二曰、寒邪伤心为疮疡。经曰。太阳司天。寒淫所胜。血变于中。发为痈疡。病本于心。又云。太阳司天之政。
三之气。寒气行。民病寒。反热中。痈疽注下。又云。阳明司天之政。四之气。寒雨降。民病痈肿疮疡是也。
三曰、燥邪伤肝为疮疡。经曰。木不及曰委和。上商与正商同。其病支发痈肿疮疡。邪伤肝也。又云。阳明
司天。燥淫所胜。民病疮疡痤痈。病本于肝是也。
四曰、湿邪疮疡。经曰。太阴司天。湿气变物。甚则身后痈。又云。太阴之胜。火气内郁。疮疡于中。流散于外
是也。
上四条天行时气也。此由外感。故曰外因。然外来之因。则肌肉血脉筋骨受之。其见症多寒热交作。筋
骨疼痛。及湿痰流注。风湿风温。时毒等类。治宜发之。如苍术复煎散、绀珠丹之类。经云。汗之则疮已。使
荣卫通行。邪气不得干于内也。又云。阳气者。开阖不得。寒气从之。乃生大偻。又云。此寒气之种。八风之
变。四时之病。以其胜者治之。此亦外因也。
人体的气血运行，与天地自然界的规律同步；人体的经络循行，与昼夜的时间变化相合。如果受到风、寒、暑、湿、燥、火六淫（六种外感病邪）的侵袭，或受喜、怒、忧、思、悲、恐、惊七情（七种情志活动）的损伤，加之饮食没有定时，房事生活不节制，导致阴阳失调，营气（行于脉中，具有营养作用的气）和卫气（行于脉外，具有防御作用的气）郁结阻滞，从而形成痈肿疮疡，其病因总括起来不出于“三因”（内因、外因、不内外因）。因此，在书中将“三因”作为首篇论述。
关于运气学说中的痈疽有四种情况：
第一是火热之气助长心火而引发疮疡。医经说：“少阴君火所至之时，会出现疡疹。”又说：“当少阴司天（主管上半年气候）时，热气向下临照，肺气随之上应，严重时会出现疮疡。”又说：“当少阴司天时，若补益太过导致气机壅滞，寒气开始显现，阳气被郁遏，炎暑即将兴起，体内外部都会发生疮疡。”又说：“少阳相火所至之时，会出现疮疡。”又说：“当少阳司天时，风热散布，太阴湿土之气横逆流行，寒气按时令而至，民众易患胃脘冷痛，体表发出疮疡。初之气阶段，气候偏温，病症表现为皮肤腠理间的疮；二之气阶段，火气反而被郁遏，病症表现为热邪郁结于上部，疮疡发于中部；三之气阶段，炎暑到来，民众易患脓疮。”又说：“当太阳寒水司天时，初之气阶段，气候偏温，肌肤腠理出现疮疡。”这些都属于正常的运气变化，病情较轻。又说：“少阴司天时，热气过盛，严重时出现疮疡。”又说：“少阴司天时，客气胜主气，严重时出现疮疡。”又说：“少阴之复气（报复之气），会导致疹子、痈疽、痤疮、痔疮等疾病。”又说：“火气太过称为‘赫义’，其病症为疮疽出血。”又说：“火气郁结而爆发时，民众易患疮疡痈肿。”这些属于邪气变异，病情严重。
第二是寒邪伤心引发疮疡。医经说：“当太阳司天时，寒气过盛，血液在中焦发生变化，发为痈疡。病的根本在于心。”又说：“当太阳司天时，在三之气阶段，寒气盛行，民众感到寒冷，但内部反现热象，导致痈疽、腹泻。”又说：“当阳明燥金司天时，在四之气阶段，寒雨降落，民众易患痈肿疮疡。”
第三是燥邪伤肝引发疮疡。医经说：“木运不及称为‘委和’，其表现与正常金运相同，病症为四肢发作痈肿疮疡，这是因为邪气伤害了肝脏。”又说：“当阳明司天时，燥气过盛，民众易患疮疡、痤疮、痈肿，病的根本在于肝脏。”
第四是湿邪引发的疮疡。医经说：“当太阴湿土司天时，湿气改变万物性质，严重时会导致背部生痈。”又说：“当太阴湿土胜复时，火气在内郁结，疮疡发于体内，流散于体表。”
以上四条属于天时气候流行的致病因素。这是由于外感邪气所致，所以称为“外因”。然而，外来邪气会侵犯肌肉、血脉、筋骨，其临床表现多为寒热交替发作，筋骨疼痛，以及湿痰流注、风湿、风温、时毒等类别。治疗适宜采用发散法，如苍术复煎散、绀珠丹之类的方剂。医经说：“通过发汗可以使疮疡痊愈”，目的是使营卫之气通行无阻，邪气不能侵入体内。又说：“阳气者的开阖功能失常，寒气乘虚而入，就会形成严重的脊柱弯曲（大偻）。”又说：“这是寒气的种类，由八风（八方之风）的变化引起，属于四季的疾病，应当用克制它的五行属性来治疗。”这也属于外因范畴。
The Qi and Blood of the human body flow in accordance with the laws of Heaven and Earth; the meridians (Jingluo) of the human body circulate in sync with the cycle of day and night. If one is affected by the Six Evils (Liu Yin, six external pathogenic factors: wind, cold, summer-heat, dampness, dryness, fire), injured by the Seven Emotions (Qi Qing, seven emotional activities: joy, anger, worry, thought, grief, fear, fright), or suffers from irregular diet and immoderate sexual activity, it leads to a disorder of Yin and Yang. When Ying Qi (nutritive Qi) and Wei Qi (defensive Qi) become stagnant and knotted, carbuncles and sores (Yong) form. These causes generally fall under the "Three Categories of Etiology" (San Yin). Therefore, the text begins with the discussion of the Three Causes.
There are four types of carbuncles and sores related to the Five Movements and Six Qi (Yunqi):
First, Fire-Heat assists Heart Fire to cause sores. The Classics state: "When Shao Yin (Lesser Yin) prevails, ulcers and rashes occur." It also says: "When Shao Yin governs the year, Heat descends, causing Lung Qi to rise in response; severely, this results in sores." Furthermore: "When Shao Yin governs, if tonification leads to Qi stagnation, Cold begins to appear, suppressing Yang Qi. As scorching heat rises, sores appear both internally and externally." Also: "When Shao Yang (Lesser Yang) prevails, sores occur." And: "When Shao Yang governs, Wind-Heat spreads, while Tai Yin (Greater Yin) Dampness flows excessively. Cold arrives at its proper time, causing people to suffer from internal cold and external sores. In the First Qi phase, the climate is too warm, leading to sores in the skin and interstices. In the Second Qi phase, Fire is suppressed, leading to Heat stagnating above and sores appearing in the middle. In the Third Qi phase, scorching heat arrives, causing people to suffer from pustular sores." Additionally: "When Tai Yang (Greater Yang) governs, in the First Qi phase, the climate is too warm, resulting in sores on the skin and interstices." These represent normal transformations, indicating mild disease. Further: "When Shao Yin governs, excessive Heat wins, severely causing sores." Also: "When Shao Yin governs, if the Guest Qi (Ke) overcomes the Host Qi (Zhu), severely sores occur." Also: "The Rebound of Shao Yin causes rashes, carbuncles, sores, acne, and hemorrhoids." Also: "Excessive Fire is called 'He Yi', causing sores and abscesses with bleeding." Also: "When Fire is depressed and erupts, people suffer from sores and swelling." These represent pathological changes, indicating severe disease.
Second, Cold Evil injures the Heart to cause sores. The Classics state: "When Tai Yang governs, excessive Cold wins, altering blood in the interior, manifesting as carbuncles and sores. The root of the disease lies in the Heart." Also: "When Tai Yang governs, in the Third Qi phase, Cold Qi dominates. People feel cold, but experience internal heat, leading to carbuncles, sores, and diarrhea." Also: "When Yang Ming (Bright Yang) governs, in the Fourth Qi phase, cold rain falls, causing people to suffer from swelling, sores, and ulcers."
Third, Dryness Evil injures the Liver to cause sores. The Classics state: "When Wood is deficient, it is called 'Wei He'. Its manifestation is similar to correct Metal Qi. The disease involves limb eruptions, swelling, sores, and ulcers, due to evil injuring the Liver." Also: "When Yang Ming governs, excessive Dryness wins, causing people to suffer from sores, acne, and carbuncles. The root of the disease lies in the Liver."
Fourth, Dampness Evil causes sores. The Classics state: "When Tai Yin governs, Dampness alters things. Severely, this leads to sores on the back." Also: "When Tai Yin prevails, Fire Qi stagnates internally, causing sores within that spread outward."
The above four categories belong to epidemic Qi transmitted through the heavens. These arise from external contraction, hence termed "External Causes." However, exogenous pathogens affect muscles, blood vessels, and sinews/bones. Symptoms often include alternating chills and fever, pain in sinews and bones, as well as wandering phlegm-dampness, wind-dampness, wind-warmth, and seasonal toxins. Treatment should favor dispersing methods, such as Cang Zhu Fu Jian San (Atractylodes Decoction for Double Decoction) or Gan Zhu Dan (Cyan Pearl Pill). The Classics say: "Sweating will cure the sore," aiming to unblock Ying and Wei Qi so that evil cannot invade internally. It also states: "If the opening and closing functions of Yang Qi fail, Cold Evil enters, resulting in severe curvature of the spine (Da Lou)." It further explains: "This is the nature of Cold Evil, arising from changes in the Eight Winds (Ba Feng) and seasonal diseases. Treat them using the element that conquers them." This also belongs to External Causes.