其年疫气盛行，所患皆重，最能传染，即童辈皆知言其为疫。至于微疫，反觉无有
，盖毒瓦斯所钟有浓薄也。
其年疫气衰少，闾里所患者不过几人，且不能传染，时师皆以伤寒
为名，不知者固不言疫，知者亦不便言疫。然则何以知其为疫？盖脉证与盛行之年所患之证
纤悉相同，至于用药取效，毫无差别。是以知温疫四时皆有，常年不断，但有多寡轻重耳。
疫气不行之年，微疫转有，众人皆以感冒为名，实不知为疫也。设用发散之剂，虽不合病
，
然亦无大害，疫自愈，实非药也，即不药亦自愈。至有稍重者，误投发散，其害尚浅，若误
用补剂及寒凉，反成痼疾，不可不辨。
所谓杂气者，虽曰天地之气，实由方土之气也。盖其气从地而起，有是气则有是
病，譬如所言天地生万物，然亦由方土之产也。但植物藉雨露而滋生，动物藉饮食而颐养。
盖先有是气，然后有是物。推而广之，有无限之气，因有无限之物也。但二五之精，未免生
克制化，是以万物各有宜忌，宜者益而忌者损，损者制也。故万物各有所制，如猫制鼠，如
鼠制象之类，既知以物制物，即知以气制物矣。以气制物者，蟹得雾则死，枣得雾则枯之类
，此有形之气，动植之物皆为所制也。至于无形之气，偏中于动物者，如牛瘟、羊瘟、鸡瘟
、鸭瘟，岂但人疫而已哉？然牛病而羊不病，鸡病而鸭不病，人病而禽兽不病，究其所伤不
同，因其气各异也。知其气各异，故谓之杂气。夫物者气之化也，气者物之变也，气即是物
，物即是气，知气可以知物，则知物之可以制气矣。夫物之可以制气者药物也，如蜒蚰解蜈
蚣之毒，猫肉治鼠 之溃，此受物气之为病，是以物之气制物之气。犹或可测。至于受无形杂气为病，莫
知何物之能制矣。惟其不知何物之能制，
故勉用汗、吐、下三法以决之。嗟乎！即三法且不能尽善，况乃知物乎？能知以物制气，一病
只有一药之到病已，不烦君臣佐使品味加减之劳矣。
那一年，疫气盛行，人们患的病都很严重，传染性极强，即使是儿童也知道称它为“疫”。至于轻微的疫病，反而觉得没有，这是因为毒气的聚集有浓淡之分。
那一年，疫气衰少，乡里间患病的人不过几个，而且不能传染，当时的医生都将其命名为“伤寒”，不知情的人固然不说它是疫，知情的人也不便说是疫。然而凭什么知道它是疫呢？因为脉象和症状与疫气盛行之年所患的症状完全相同，至于用药取得疗效，也毫无差别。因此可知温疫四季都有，常年不断，只是有多寡轻重罢了。
在疫气不流行的年份，偶尔出现轻微疫病，众人都称之为“感冒”，实际上并不知道那是疫。如果此时使用发散（解表）的药剂，虽然不符合病机，但也没有大害，疫病会自愈，这其实不是药的作用，即使不吃药也会自愈。到了病情稍重的情况，误用发散法，危害还较浅；如果误用补益剂及寒凉药，反而会成为顽固性疾病，这一点不可不辨别。
所谓“杂气”，虽然说来源于天地之气，实际上是由各地方的地气形成的。这种气从地面升起，有了这种气就有了这种病，譬如常说天地生成万物，但也取决于地方特产。植物依靠雨露而滋生，动物依靠饮食而颐养。先有这种气，然后才有这种物。推而广之，有无限的气，因而有无限的物。但是阴阳五行（二五）的精气，难免产生生克制化的关系，所以万物各有适宜和禁忌，适宜的则受益，禁忌的则受损，受损是因为受到制约。因此万物各自有所制约，比如猫制约老鼠，老鼠制约大象之类。既然知道可以用物来制约物，也就知道可以用气来制约物了。用气来制约物的例子，如螃蟹遇到雾气就会死，枣树遇到雾气就会枯萎之类，这是有形的气，动植物的物体都被它制约。至于无形的气，偏重于伤害动物的，如牛瘟、羊瘟、鸡瘟、鸭瘟，难道只有人得的疫病吗？然而牛生病而羊不生病，鸡生病而鸭不生病，人生病而禽兽不生病，究其受伤不同，是因为气各不相同。知道气各不相同，所以称之为杂气。物是气的变化，气是物的转化，气就是物，物就是气，知道气就可以知道物，那么就知道物可以制约气了。能够用物来制约气的，是药物，比如蜒蚰（蜗牛）能解蜈蚣的毒，猫肉能治老鼠咬伤溃烂，这是受物气致病，所以用物的气来制约物的气，这还可以推测。至于受无形杂气致病，就不知道什么物能制约它了。正因为不知道什么物能制约它，所以勉强使用汗、吐、下三种方法来解决。唉！即使这三种方法也不能尽善尽美，何况是了解事物呢？如果能知道用物来制约气，一种病只有一种药到达病灶就能痊愈，不需要烦劳君臣佐使各味药的加减配伍了。
In that year, the epidemic qi (pathogenic factors causing infectious diseases) prevailed, and the illnesses suffered were severe with high contagiousness; even children knew to call it "epidemic" (Yi). As for mild epidemics, they seemed non-existent, due to the varying density of the toxic qi accumulation.
In another year, the epidemic qi was weak, with only a few people in the neighborhoods affected, and no transmission occurred. Contemporary physicians named it "Shanghan" (Cold Damage), and those unaware naturally did not call it an epidemic, while those who knew also hesitated to label it as such. So how could one identify it as an epidemic? Because the pulse and symptoms were identical in every detail to those seen during years of prevalent epidemics, and the therapeutic efficacy of medications was indistinguishable. Thus, it is known that Warm Epidemics (Wenyi) occur throughout all four seasons and persist year-round, differing only in degree and severity.
In years when epidemic qi does not prevail, mild cases may still occur. The general public calls them "Ganmao" (Common Cold), unaware that they are actually epidemics. If dispersing agents (Di-san agents used to induce sweating and release the exterior) are used, although they do not strictly match the pathology, there is little harm; the epidemic resolves spontaneously. This is not due to the medicine itself, as the condition would heal without treatment even so. In slightly more severe cases, misusing dispersing methods causes relatively minor harm. However, if tonifying or cold-cooling agents are mistakenly used, chronic stubborn diseases may result; this distinction must not be overlooked.
The so-called "Zaqi" (Miscellaneous Qi), though described as originating from Heaven and Earth, is actually derived from local terrestrial qi. This qi rises from the ground; where there is this qi, there is this disease. Just as it is said that Heaven and Earth generate all things, yet these things depend on local origins. Plants rely on rain and dew to grow, while animals rely on food and drink to nourish themselves. First comes the qi, then the matter. Extending this logic, infinite qi gives rise to infinite matter. However, the essence of Yin and Yang and the Five Elements inevitably undergo generation, restriction, transformation, and control. Therefore, all things have their preferences and taboos: what is favorable benefits, and what is taboo harms; harm implies restriction. Thus, all things are mutually restricted, such as cats restricting mice, or mice restricting elephants. Knowing that matter can restrict matter, one should understand that qi can also restrict matter. Examples of qi restricting matter include crabs dying in fog and jujube trees withering in fog; here, tangible qi restricts both animal and plant matter. Regarding intangible qi, which predominantly affects animals, consider cattle plague, sheep plague, chicken plague, and duck plague—are humans the only ones affected by epidemics? Yet, cattle get sick while sheep do not, chickens get sick while ducks do not, and humans get sick while livestock do not. This difference in injury arises because the qi varies. Recognizing that the qi differs leads to the term "Miscellaneous Qi." Matter is the transformation of qi, and qi is the change of matter; qi is matter, and matter is qi. Understanding qi allows one to understand matter, and thus understanding that matter can restrict qi. Medicines are substances that can restrict qi. For instance, slugs (Yanyou) resolve the toxicity of centipedes, and cat meat treats ulcers caused by rat bites. These are illnesses caused by receiving matter-qi, treated by using the qi of matter to counteract the qi of matter—a phenomenon that can be deduced. However, for illnesses caused by receiving intangible miscellaneous qi, it is unknown what substance can restrict it. Precisely because the specific restricting agent is unknown, physicians reluctantly resort to the three methods of Sweating (Han), Vomiting (Tu), and Purging (Xia) to resolve the condition. Alas! Even these three methods are not perfect, let alone knowing the specific substances. If one could know how to use matter to restrict qi, a single disease would be cured by a single herb reaching the target, eliminating the need for complex formulations involving Sovereign, Minister, Assistant, and Courier herbs and their adjustments.