古方所用之药，当时效验显著，而本草载其功用凿凿者，今根据方施用，竟有应与不应，
其故
何哉？盖有数端焉∶一则地气之殊也。当时初用之始，必有所产之地，此乃其本生之土，故
气浓而力全；以后传种他方，则地气移而力薄矣。一则种类之异也。凡物之种类不一，古人
所采，必至贵之种。后世相传，必择其易于繁衍者而种之，未必皆种之至贵者。物虽非伪，
而种则殊矣。一则天生与人力之异也。当时所采，皆生于山谷之中，元气未泄，故得气独浓
。今皆人功种植，既非山谷之真气，又加灌溉之功，则性平淡而薄劣矣。一则名实之讹也。
当时药不市卖，皆医者自取而备之。迨其后，有不常用之品，后人欲得而用之，寻求采访，
或误以他物充之，或以别种代之。又肆中未备，以近似者欺人取利，此药遂失其真矣。其变
迁之因，实非一端。药性既殊，即审病极真，处方极当，奈其药非当时之药，即效亦不可必
矣。今之医者，惟知定方，其药则惟病家取之肆中，所以真假莫辨。虽有神医，不能以假药
治真病也。
药之治病，有可解者，有不可解者。如性热能治寒，性燥能治湿。芳香则通气，滋润则
生津
，此可解者也。如同一发散也，而桂枝则散太阳之邪，柴胡则散少阳之邪。同一滋阴也，而
麦冬则滋肺之阴，生地则滋肾之阴。同一解毒也，而雄黄则解蛇虫之毒，甘草则解饮食之毒
，已有不可尽解者。至如鳖甲之消痞块，使君子之杀蛔虫，赤小豆之消肤肿，蕤仁生服不眠
，熟服多眠，白鹤花之不腐肉而腐骨，则万不可解者。此乃药性之专长，即所谓单方秘方也
。然人只知不可解者之为专长，而不知常用药之中，亦各有专长之功。后人或不知之，而不
能用，或日用而忽焉，皆不能尽收药之功效者也。知医者，当广集奇方，深明药理，然后奇
症当前，皆有治法，变化不穷。当年神农着《本草》之时，既不能睹形而即识其性，又不可
每药历试而知，竟能深识其功能，而所投必效，岂非与造化相为默契，而非后人思虑之所能
及者乎？
古代方剂中使用的药物，在当时疗效显著，且《本草》明确记载其功效的，如今依据古方使用，竟然有适用与不适用之分，这是什么原因呢？大概有几个方面：一是地域气候的差异。刚开始使用时，必定有其产地，那是它原本生长的土地，所以药气浓厚而力量完整；后来传播种植到其他地方，地域气候改变，药效就变薄弱了。二是种类的差异。凡是物品的种类不止一种，古人所采集的，一定是最高贵的品种。后世相传，一定选择容易繁衍的品种来种植，未必都是最高贵的品种。物品虽然不是假的，但品种却不同了。三是天然生成与人工培育的差异。当时所采集的，都生长在山谷之中，元气没有泄露，所以得气特别浓厚。现在都是人工种植，既不是山谷中的真气，又加上灌溉的人工功夫，那么药性就变得平淡而低劣了。四是名称与实际不符的错误。当时药物不上市售卖，都是医生自己采集准备的。等到后来，有不常用的药材，后人想要得到并使用，寻求采访，或者误用其他物品冒充，或用别的品种替代。又有药店里没备货，用近似的东西欺骗人谋取利益，这种药于是失去了真实性。其变化的原因，实在不只一端。药性既然不同，即使诊断病情极其准确，处方极其恰当，无奈药物已经不是当时的药物，即使有效也不能保证。现在的医生，只知道确定方子，药物则只从病家所在的药店获取，所以真假难以分辨。虽然有神医，也不能用假药治疗真病。
药物治病，有可以解释清楚的，有无法解释清楚的。比如药性热能治寒证，药性燥能治湿证。芳香的能通气，滋润的能生津液，这些是可以解释的。同样是发散表邪，桂枝（Cinnamon Twig）则发散太阳经（Taiyang channel）的邪气，柴胡（Bupleuri Radix）则发散少阳经（Shaoyang channel）的邪气。同样是滋阴，麦冬（Ophiopogonis Radix）则滋养肺阴，生地黄（Rehmanniae Radix）则滋养肾阴。同样是解毒，雄黄（Realgar）则解蛇虫之毒，甘草（Glycyrrhizae Radix et Rhizoma）则解饮食之毒，这已经不能完全解释了。至于像鳖甲（Trionycis Carapax）消除痞块，使君子（Quisqualis Fructus）杀灭蛔虫，赤小豆（Phaseoli Semen Rubrum）消除皮肤肿胀，蕤仁（Prunus cerasiformis seed）生服使人不眠，熟服使人多眠，白鹤花（Hemidesmus indicus root? Note: Context implies a specific herb with bone-rotting property, likely referring to a toxic plant or specific traditional usage, keeping as 白鹤花）不腐蚀肌肉而腐蚀骨头，这些是万万无法解释的。这是药性的专长，也就是所谓的单方秘方。然而人们只知道无法解释的是专长，却不知道常用药物中，也各有专长的功效。后人有的不知道，所以不能使用；有的日常使用却忽略了这一点，都不能完全收尽药物的功效。懂医术的人，应当广泛收集奇方，深刻理解药理，然后面对疑难病症时，都有治疗方法，变化无穷。当年神农撰写《本草》的时候，既不能看到形状就立即识别其性质，也不可能每种药都逐一尝试来了解，竟然能深刻认识其功能，而且投药必有效，这难道不是与自然造化暗中契合，而不是后人思虑所能达到的吗？
The herbs used in ancient prescriptions produced significant effects at that time, and their functions were clearly recorded in the *Bencao* (Materia Medica). However, when applied according to these ancient prescriptions today, there are cases where they are appropriate and others where they are not. What is the reason for this? There are several factors: First, the difference in local climate and geography. When initially used, there was necessarily a place of origin; this was the native soil where they grew, so their qi (vital energy) was dense and their potency complete. Later, when propagated to other regions, the change in local environment led to diminished potency. Second, the difference in species. The varieties of any substance are not uniform. The ones collected by the ancients were invariably the most precious varieties. In later generations, people chose varieties that were easy to propagate for cultivation, which were not necessarily the most precious ones. Although the substances were not counterfeit, the species differed. Third, the difference between natural growth and human cultivation. Herbs collected at that time all grew in mountain valleys, where their primordial qi had not been depleted, thus acquiring a particularly dense qi. Today, all are cultivated artificially; lacking the true qi of mountain valleys and subjected to irrigation efforts, their nature becomes bland and inferior. Fourth, errors in nomenclature versus reality. At that time, medicines were not sold in markets but were gathered and prepared by physicians themselves. Later, for rarely used items, those who sought to obtain and use them might mistakenly substitute other substances or replace them with different species. Furthermore, shops lacking stock might deceive customers with similar-looking substitutes for profit, causing the medicine to lose its authenticity. The reasons for these changes are manifold. Since the medicinal properties differ, even if the diagnosis of the disease is extremely accurate and the prescription is perfectly appropriate, the fact remains that the medicine is no longer the same as it was then, and efficacy cannot be guaranteed. Modern physicians only know how to determine the prescription; the herbs are obtained by patients from local pharmacies, making it difficult to distinguish between authentic and fake products. Even a divine physician cannot treat a genuine disease with counterfeit medicine.
In treating diseases, some aspects of herbal action can be explained, while others cannot. For instance, hot-natured herbs can treat cold syndromes, and dry-natured herbs can treat dampness. Aromatic herbs can promote the flow of qi, and moistening herbs can generate body fluids; these are explainable. However, consider dispersion: Guizhi Tang (Cinnamon Twig Decoction) dispels pathogenic factors from the Taiyang channel (Solar channel), whereas Chaihu (Bupleuri Radix) dispels pathogenic factors from the Shaoyang channel (Lesser Yang channel). Consider nourishing yin: Maidong (Ophiopogonis Radix) nourishes lung yin, whereas Shengdi Huang (Rehmanniae Radix) nourishes kidney yin. Consider detoxification: Xionghuang (Realgar) detoxifies snake and insect venom, whereas Gancao (Glycyrrhizae Radix et Rhizoma) detoxifies food poisoning; these cannot be fully generalized. As for Bi Jia (Trionycis Carapax) eliminating masses, Shi Jun Zi (Quisqualis Fructus) killing roundworms, Chi Xiao Dou (Phaseoli Semen Rubrum) reducing skin edema, Rui Ren (Prunus cerasiformis seed) causing insomnia when taken raw and drowsiness when cooked, and Bai He Hua (Hemidesmus indicus root/flower) rotting bone without affecting flesh—these are utterly inexplicable by general principles. These represent the specialized functions of herbs, what is referred to as single-herb formulas or secret recipes. Yet people only recognize the inexplicable as specialized functions, failing to realize that commonly used herbs also possess specific specialized efficacies. Later generations either do not know this and thus fail to use them effectively, or use them daily without recognizing these specific attributes, thereby failing to fully harness the benefits of the herbs. A knowledgeable physician should extensively collect unique prescriptions and deeply understand herbal pharmacology, so that when facing rare or complex conditions, there are always treatment methods available, allowing for infinite adaptability. When Shen Nong compiled the *Bencao*, he could not identify the nature of a herb merely by its appearance, nor could he test every herb individually to learn its properties. Yet he was able to profoundly comprehend their functions, ensuring that his applications were always effective. Was this not a tacit understanding with the creative forces of nature, far beyond the reach of later generations' intellectual reasoning?