方脉所主，病证多端，总其纲要，不出外感、内伤两门。然外感则有风、寒、暑、湿、燥、火之异，其为
病不同，而治法迥别，故仲景分六经证治，以辨阴阳、表里、虚实、寒热，此《伤寒论》一书，首当体究者
也。夫伤寒传里，则变为热，要在辨邪之浅深。若表邪未解，必先解表，方可治里，此而错误，反使外邪内陷
而成危证。其有初感风寒，直入于阴者，因其本元不足，则当温中助阳，不可误发其表，仲景皆已详辨者也。
惟大江以南，风寒无北方之厉，略用辛温表散即解，其内传者，多由初治失当，致表气反闭而变重病，此辨证
不明之故也。盖风由阳气所化，经言风为百病之长，善行而数变，故随寒、热、温、凉之气而变，时令寒则为
风寒，时令温则为风温。自霜降后，寒气日甚，及冬至一阳下升，至立春阳气始出于地，阴气自上而降者尚盛，
故寒邪多也；春分以后，阳渐上升，阴渐入地，其气方温，至巳月而阳尽升地上，则寒少矣。故经言夏至前病
名温，夏至后病名暑。温者，纯阳之气，温甚，则为火邪矣。其名暑者，夏至一阴下升，阳气上降，阴阳变
迁，火湿合化之气也。故人身之气，亦随之而变。夏至前人身内阳外阴，或有寒邪，易于化热；夏至后外阳内
阴，而暑由火湿合化，湿为阴邪，故不可轻投寒剂，而暑病古方，有用姜、附、玉桂者，皆本阴阳至理，而与
温热之邪治法不同，学人不可不知也。若秋燥之气，亦有阴、阳、寒、热之异，余前集《六气论》中，俱已辨
晰。此为外感之大略也。若夫内伤杂证，仲景《金匮要略》已明大纲，要在分别虚实两端。凡七情妄动而伤本元
者，为虚；饮食不调而有积滞者，为实。其虚者，须辨阴阳、气血。阴阳根于肾元，气血生自脾胃。故伤气血
者，调补脾胃尚易；伤阴阳者，培其肾元为难。如其阴损，而脾胃强、大便固者，可用滋润养阴之法；倘脾胃
弱，而兼大便滑者，阳亦伤矣，不可治也。其阳损者，脾胃弱而便不固，必能受助阳之药为吉；如不能受，阴
亦枯矣，不可治也。其有阴阳虽伤，而脾胃尚强者，调理得宜，犹可带病延年；如阴阳虽非无根，而脾胃先败
者，终归不起。故经曰∶有胃气则生，无胃气则死也。若由饮食、劳倦而伤脾胃，轻者可以调治，久伤不复，
必至阴阳俱败，以无生化之源也。此皆内伤之大略也。且如纯虚纯实，而可用补用泻之病少；内伤外感，虚实
夹杂之病多。变幻多端，莫可测识。苟非洞明阴阳、气血生化之理，脏腑、经络浅深之殊，则不能辨本元之虚
实，病邪之所由，难免误治之失矣。此《内经》之不可
不研究以明之也。本门所集病证，有未尽者，当于四诊、脏腑、经络诸门，参合观之。至于六气流行，主客
变化，每有酿成疫疠者，经分金、木、水、火、土五疫，详运气门中。如能悟其至理，病变虽多，皆可一以
贯之。故方脉为诸科领袖，则神而明之，存乎其人也。
方书脉法所论述的疾病证候繁多，总括其纲要，不外乎外感和内伤两大类。然而外感病又有风、寒、暑、湿、燥、火六淫之异，它们致病不同，治疗方法也截然不同，所以张仲景将疾病分为六经（太阳、阳明、少阳、太阴、少阴、厥阴）进行辨证论治，以辨别阴阳、表里、虚实、寒热，这是《伤寒论》一书首要深入探究的内容。伤寒邪气传入体内，会转化为热证，关键在于辨别邪气的深浅。如果表邪未解，必须先解除表邪，然后才能治疗里证，若在此处出错，反而会使外邪内陷而形成危重证候。那些初感风寒，直接侵入阴经的，是因为患者本元不足，此时应当温中助阳，不可误用发汗解表的方法，这些张仲景都已详细辨析了。只有长江以南地区，风寒不像北方那样猛烈，稍微使用辛温解表的药物即可痊愈，其病情向内传变的，多是因为初期治疗不当，导致表气闭塞反而变成重病，这是辨证不明造成的。大概风气是由阳气变化而来的，医经说风是百病的先导，善于游走且变化迅速，所以它随着寒、热、温、凉的气候而变化，时令寒冷就是风寒，时令温暖就是风温。自霜降之后，寒气日益加重，直到冬至一阳初生开始上升，到立春阳气才从地下发出，此时自上而降的阴气仍然旺盛，所以寒邪较多；春分以后，阳气逐渐上升，阴气逐渐入地，气候方才温和，到了巳月（农历四月）阳气完全升于地上，那么寒邪就少了。所以医经说夏至前得的病名叫温病，夏至后得的病名叫暑病。温病，是纯阳之气，温气过盛，就变成了火邪。所谓暑病，是夏至时一阴初生开始下降，阳气上降，阴阳变迁，是火与湿气化合而成的气候。所以人体的气机也随之变化。夏至前人体内部阳气盛而外部阴气盛，若有寒邪，容易化热；夏至后人体外部阳气盛而内部阴气盛，而暑病由火湿化合而成，湿属于阴邪，所以不可轻易投用寒凉药物，而古代治疗暑病的方剂中，有用干姜、附子、肉桂的，这都是基于阴阳至理，与温热邪气的治疗方法不同，学习者不可不知道。至于秋季的燥气，也有阴、阳、寒、热的区别，我在之前的《六气论》中都已经辨析清楚。这是外感病的大略情况。至于内伤杂病，张仲景的《金匮要略》已经明确了大纲，关键在于分别虚证和实证两端。凡是七情妄动而损伤本元的，属于虚证；饮食不调而有积滞的，属于实证。其中的虚证，必须辨别阴阳、气血。阴阳根源于肾元，气血生成于脾胃。所以损伤气血的，调理补益脾胃还比较容易；损伤阴阳的，培补肾元就比较困难。如果是阴精亏损，但脾胃功能强、大便干燥的，可以使用滋润养阴的方法；倘若脾胃虚弱，并且兼有大便滑泄的，阳气也已经受伤了，这就难以治疗了。如果是阳气亏损，脾胃虚弱且大便不固，一定能够耐受助阳的药物才是吉兆；如果不能耐受，阴精也就枯竭了，这也是难以治疗的。如果有阴阳虽然受损，但脾胃尚且强健的，只要调理得当，还可以带病延年；如果阴阳虽然并非无根，但脾胃先衰败的，最终终究无法挽回。所以医经说：有胃气就能生存，无胃气就会死亡。如果是由于饮食、劳倦而损伤脾胃，轻症可以调治，久病损伤不能恢复，必然导致阴阳俱败，因为没有生化之源了。这些都是内伤病的大略情况。况且纯粹虚证或纯粹实证，可以用补法或用泻法治疗的病较少；内伤和外感夹杂，虚实并见的病较多。病情变幻多端，难以预测识别。如果不是透彻明白阴阳、气血生化的道理，脏腑、经络深浅的差异，就不能辨别本元的虚实，以及病邪的来源，难免出现误治的错误。这就是《内经》不可不深入研究以弄懂它的原因。本门汇集的病证，有不详尽的，应当在四诊（望、闻、问、切）、脏腑、经络各门类中，参考综合观察。至于六气流行，主气和客气的变化，每每有酿成疫疠的，医经将其分为金、木、水、火、土五类疫病，详见运气学说门类中。如果能领悟其中的至理，病变虽然多，都可以用一个道理贯穿起来。所以方脉诊断是各科的领袖，能否神妙地阐明它，取决于人本身。
The diseases and syndromes discussed in medical texts and pulse diagnosis are numerous, but summarizing their essentials, they do not go beyond the two categories of External Contraction (Wai Gan) and Internal Injury (Nei Shang). However, External Contraction involves differences among Wind, Cold, Summerheat, Dampness, Dryness, and Fire. Since they cause different diseases, their treatment methods are distinctly different. Therefore, Zhang Zhongjing divided the diseases into Six Stages (Taiyang, Yangming, Shaoyang, Taiyin, Shaoyin, Jueyin) for syndrome differentiation and treatment, to distinguish Yin and Yang, Exterior and Interior, Deficiency and Excess, Cold and Heat. This is the primary content that must be thoroughly studied in the *Treatise on Cold Damage Pathogens* (*Shanghan Lun*). When Cold damage pathogens transmit inward, they transform into Heat syndromes; the key lies in distinguishing the depth of the pathogen. If the Exterior pathogen has not been resolved, one must first resolve the Exterior before treating the Interior. Making an error here may cause the external pathogen to sink inward, resulting in critical conditions. In cases where initial contraction of Wind and Cold directly enters the Yin channels, due to insufficiency of the patient's original Qi, one should warm the Middle and assist Yang, and must not mistakenly induce sweating to release the Exterior. Zhang Zhongjing has already detailed these distinctions. Only in the regions south of the Yangtze River, where Wind and Cold are not as severe as in the North, slight use of Acrid-Warm exterior-releasing herbs can resolve the condition. Cases transmitting inward often result from improper initial treatment, causing the Exterior Qi to become closed and the disease to worsen, which is due to unclear syndrome differentiation. Generally, Wind is transformed from Yang Qi. The classics state that Wind is the leader of a hundred diseases; it moves freely and changes frequently, so it varies with Cold, Heat, Warmth, and Coolness. In cold seasons, it is Wind-Cold; in warm seasons, it is Wind-Warmth. After Frost Descent, Cold Qi intensifies daily. Until Winter Solstice, when a single Yang begins to rise from below, and until Start of Spring when Yang Qi emerges from the earth, the Yin Qi descending from above remains strong, so Cold pathogens are prevalent. After Spring Equinox, Yang gradually rises and Yin gradually sinks into the earth, and the climate becomes warm. By the Si month (lunar April), Yang Qi fully ascends above ground, so Cold pathogens decrease. Thus, the classics state that diseases occurring before Summer Solstice are named Warm Diseases, while those after Summer Solstice are named Summerheat Diseases. Warmth refers to pure Yang Qi; when warmth is excessive, it becomes Fire pathogen. Summerheat is named so because at Summer Solstice, a single Yin begins to descend while Yang descends from above. The transformation of Yin and Yang creates an atmosphere of combined Fire and Dampness. Consequently, the Qi of the human body also changes accordingly. Before Summer Solstice, the human body has abundant internal Yang and deficient external Yin; if there is a Cold pathogen, it easily transforms into Heat. After Summer Solstice, the body has abundant external Yang and deficient internal Yin. Since Summerheat is formed by the combination of Fire and Dampness, and Dampness is a Yin pathogen, one must not lightly administer Cold medicines. Ancient formulas for treating Summerheat sometimes use Sheng Jiang (Prepared Ginger), Fu Zi (Aconite Lateralis Radix Praeparata), and Rou Gui (Cinnamon Bark), all based on the profound principles of Yin and Yang, differing from the treatment methods for Warm-Heat pathogens. Students must understand this. As for Autumn Dryness, there are also differences in Yin, Yang, Cold, and Heat, which I have clearly distinguished in my previous work, *Six Qi Theory*. This is the general overview of External Contraction. Regarding miscellaneous Internal Injury syndromes, Zhang Zhongjing’s *Essential Prescriptions Worth a Thousand Gold for Emergencies* (*Jingui Yaolue*) has clarified the main outline, focusing on distinguishing between Deficiency and Excess. Any injury to the Original Qi caused by erratic emotional movements is Deficiency; any accumulation caused by irregular diet is Excess. For Deficiency syndromes, one must distinguish between Yin/Yang and Qi/Blood. Yin and Yang are rooted in Kidney Yuan (Original Qi), while Qi and Blood are generated from Spleen and Stomach. Therefore, injuries to Qi and Blood are relatively easy to treat by regulating and tonifying the Spleen and Stomach; injuries to Yin and Yang are difficult to treat by nourishing the Kidney Yuan. If Yin essence is damaged but the Spleen and Stomach are strong and stools are firm, moistening and nourishing Yin methods can be used. However, if the Spleen and Stomach are weak and accompanied by loose stools, Yang is also injured, making it untreatable. If Yang is damaged, and the Spleen and Stomach are weak with unconsolidated stools, the patient must be able to tolerate Yang-assisting herbs for a favorable outcome; if they cannot tolerate them, Yin essence is also withered, making it untreatable. If both Yin and Yang are injured but the Spleen and Stomach remain strong, proper regulation can still allow the patient to live with the illness for a long time. If Yin and Yang are not without root, but the Spleen and Stomach fail first, recovery is ultimately impossible. Thus, the classics say: "With Stomach Qi, there is life; without Stomach Qi, there is death." If the Spleen and Stomach are injured by diet or overwork, mild cases can be regulated; chronic injury without recovery will inevitably lead to the failure of both Yin and Yang, due to the lack of the source of generation and transformation. These are the general overview of Internal Injuries. Moreover, purely Deficient or purely Excess conditions suitable for Tonification or Purging are few; most diseases involve mixed Internal Injury and External Contraction, with simultaneous Deficiency and Excess. Conditions change endlessly and are unpredictable. Unless one thoroughly understands the principles of Yin-Yang and the generation/transformation of Qi-Blood, and the differences in depth among Zang-Fu organs and meridians, one cannot distinguish the Deficiency/Excess of the Original Qi and the origin of pathogens, inevitably leading to misdiagnosis and mistreatment. This is why the *Inner Canon of the Yellow Emperor* (*Neijing*) must be studied to clarify its principles. The syndromes collected in this section may be incomplete; they should be cross-referenced with sections on Four Diagnostic Methods (Inspection, Auscultation-Olfaction, Inquiry, Palpation), Zang-Fu Organs, and Meridians. Regarding the circulation of the Six Qi, and the changes between Host and Guest Qi, epidemics are often brewed. The classics divide these into five epidemics corresponding to Metal, Wood, Water, Fire, and Earth, detailed in the Section on Luck (Yun Qi). If one can comprehend these profound principles, despite the variety of pathological changes, they can all be understood through a single principle. Therefore, Pulse Diagnosis and Formula Medicine are the leaders of all medical specialties; whether one can divine and illuminate them depends on the individual.