经曰。巨阳者。诸阳之属也。其脉连于风府。故为诸阳主气也。又曰。伤寒一
日巨阳受之。头项痛。腰脊强。以其经从头项下肩膊挟脊抵腰中。其所统
者大。其所循者远。故易以犯。犯之则恶寒发热。独甚于他经。仲景以麻黄
汤发之。此有是太阳症。用是太阳药也。若在阳明。则热多而寒少。无是症
矣。在少阳。则寒往而热来。亦无是症矣。传入三阴。则有热而无寒。更无是
症矣。故惟太阳一经。寒独甚。脉独紧。汗独无。未传阳明。则口不渴。未传少
阳。则耳不聋。仲景用麻黄汤为太阳之正治。固非易老九味羌活汤之所
能代也。若苟非太阳而阳明。则用葛根汤。非太阳而少阳。则用柴胡汤。均
非麻黄汤之可假借也。虽然太阳一经。非独冬时严寒。能触犯之。而四时
寒邪。皆能犯之。如犯之而身果寒。脉果紧。其症具在。即四时皆用麻黄可
也。如犯之而寒不甚。紧不盛。其症虽具。即冬时不用麻黄可也。况作劳辛
苦之人。及本元亏损之后。而偶冒寒邪。脉紧少力者。又当从权以治。不必
执用麻黄可也。盖以麻黄骁悍之性。攻邪固易。损正不难。一误投之。为变
不测。可不慎乎。
按麻黄汤。为太阳经正药。余所以谆谆慎之者。盖非其时。非其经。非其
人之质足以当之。鲜不为害。请勿轻试。为天下幸甚。
治验
一友积劳后。感寒发热。医者不审。以麻黄汤进。目赤鼻衄。痰中带血。继以
小柴胡汤。舌干乏津。余诊之。脉来虚数无力。乃劳倦而兼阴虚候也。误
投热药。能不动血而竭其液耶。连进地黄汤三剂。血止而神尚未清。用
生脉散及归脾汤去 术投之。神虽安而舌仍不生津。予曰。肾主五液。
而肺为生化之源。滋阴益气。两不见效。何也。余熟思之。乃悟麻黄性不
内守。服之而竟无汗。徒伤其阴。口鼻见血。而药性终未发泄。故津液不
行。予仍以生脉散固其本。用葛根陈皮引之。遂得微汗。舌果津生。后以
归脾汤六味丸而痊。
一医者素自矜负。秋月感寒。自以麻黄汤二剂饮之。目赤唇焦。裸体罔顾。
遂成坏症。
一药客感冒风寒。自谓知药。竟以麻黄五钱服之。吐血不止而毙。此二症
虽进黄连解毒犀角地黄汤。终不挽回。大可骇也。
麻黄汤
麻黄（二钱） 桂枝（一钱） 甘草（五分） 杏仁（八粒）
加姜枣水煎
九味羌活汤
羌活 防风 苍术（各一钱） 甘草 白芷 川芎 生地黄 黄芩（各一钱五分） 细辛（七分）
加姜枣水煎
《内经》说：巨阳（即太阳经），是诸阳经的统领。它的经脉连接风府穴，所以它是诸阳经主气的经络。又说：伤寒病第一天，巨阳经受邪。症状表现为头项疼痛，腰脊僵硬。因为这条经脉从头项向下经过肩膊，夹着脊柱直达腰部中间。它所统辖的范围大，循行的路线远，所以容易受到外邪侵犯。一旦受邪，就会出现恶寒发热，且程度比其他经络更为严重。张仲景用麻黄汤来发汗解表。这是有太阳病的症状，就用治疗太阳病的药物。如果病在阳明经，则热象多而寒象少，就没有上述症状了。如果病在少阳经，则是寒热往来，也没有上述症状了。如果传入三阴经，则只有热象而没有寒象，更不会有上述症状了。所以只有太阳一经，寒象特别重，脉象特别紧，无汗特别明显。尚未传入阳明经时，口不渴；尚未传入少阳经时，耳不聋。张仲景用麻黄汤作为治疗太阳病的正治法，这确实不是易老（王好古）的九味羌活汤所能替代的。如果不是太阳病而是阳明病，则用葛根汤；不是太阳病而是少阳病，则用柴胡汤。这些都不是可以借用麻黄汤的。虽然如此，太阳一经，不仅仅是冬季严寒能触犯它，四季的寒邪都能侵犯它。如果受邪后身体确实寒冷，脉象确实紧，症状俱全，那么即使在四季都可以使用麻黄汤。如果受邪后寒象不重，脉紧不明显，即使症状具备，那么在冬季也可以不使用麻黄汤。何况是劳累辛苦的人，以及本元亏损之后，偶然冒犯寒邪，脉紧但力气少的，又应当权变处理进行治疗，不必固执地使用麻黄汤。因为麻黄具有骁悍的药性，攻伐邪气固然容易，损伤正气也不难。一旦误用，变化不可预测，能不谨慎吗？
按语：麻黄汤是太阳经的正药。我之所以反复慎重告诫，是因为如果不是相应的时令，不是相应的经络，不是相应体质的人能够承受，很少有不造成危害的。请不要轻易尝试，这对天下人都是幸事。
治验案例：
一位朋友在积劳之后，感受寒邪出现发热。医生没有仔细审察，就给他服用麻黄汤。结果导致眼睛发红、鼻出血，痰中带血。接着又用小柴胡汤治疗，导致舌干缺乏津液。我诊察他的脉象，虚数无力，这是劳倦兼阴虚的证候。误投热性药物，怎么能不动血并耗竭津液呢？连续服用地黄汤三剂，血止住了但神志仍未清醒。我用生脉散及归脾汤去掉白术投服。神志虽然安定但舌头仍然不能生津。我说：“肾主管五液，肺是生化之源。”滋阴益气两种方法都无效，为什么呢？我深思熟虑后，领悟到麻黄药性不内守，服用后竟然没有出汗，白白伤了阴液，口鼻见血，而药性终究没有发泄出来，所以津液不行。我仍然用生脉散固护根本，用葛根和陈皮引导，于是得到微汗，舌头果然生出津液。后来用归脾汤和六味丸治愈。
一位医生平时自视甚高。秋天感受寒邪，自己服用两剂麻黄汤。结果眼睛发红，嘴唇焦裂，赤身裸体不顾形象。最终成了坏病。
一位药材商人感冒风寒，自认为懂药，竟然服用五钱麻黄。吐血不止而死。这两个病例虽然进服黄连解毒汤和犀角地黄汤，最终也无法挽回，非常令人惊骇。
麻黄汤方：
麻黄（二钱） 桂枝（一钱） 甘草（五分） 杏仁（八粒）
加生姜、大枣，水煎服
九味羌活汤方：
羌活 防风 苍术（各一钱） 甘草 白芷 川芎 生地黄 黄芩（各一钱五分） 细辛（七分）
加生姜、大枣，水煎服
The *Neijing* states: Juyang (Taiyang, the Greater Yang channel) is the leader of all Yang channels. Its vessels connect to the Fengfu acupoint (GV16), thus it governs the Qi of all Yang channels. It also states: On the first day of a Shanghan (Cold Damage) disease, the Juyang channel receives the pathogen. Symptoms include pain in the head and nape, and stiffness in the lower back and spine. This is because this channel descends from the head and nape, passes through the shoulders, flanks the spine, and reaches the middle of the waist. Its jurisdiction is broad, and its pathway is long; therefore, it is easily invaded by pathogens. Once invaded, aversion to cold and fever occur, and these symptoms are more severe than in other channels. Zhang Zhongjing uses Mahuang Tang (Ephedra Decoction) to induce sweating and release the exterior. This applies when there are Taiyang symptoms, so Taiyang-specific herbs are used. If the disease is in the Yangming channel, heat predominates over cold, and the aforementioned symptoms would not be present. If the disease is in the Shaoyang channel, there is alternating chills and fever, and again, the aforementioned symptoms would not be present. If the pathogen transmits to the Three Yin channels, there is only heat without cold, and even less likely to have the aforementioned symptoms. Therefore, only in the Taiyang channel is the cold sensation particularly intense, the pulse particularly tight, and anhidrosis (absence of sweating) particularly prominent. Before transmitting to Yangming, there is no thirst; before transmitting to Shaoyang, there is no deafness. Zhang Zhongjing employs Mahuang Tang as the standard treatment for Taiyang diseases. This is indeed not replaceable by Jiwei Qianghuo Tang (Nine-Ingredient Notopterygium Decoction) created by Yi Lao (Wang Haogu). If it is not a Taiyang disease but a Yangming disease, Gegen Tang (Pueraria Decoction) should be used; if it is not a Taiyang disease but a Shaoyang disease, Chaihu Tang (Bupleurum Decoction) should be used. None of these can borrow or substitute for Mahuang Tang. Nevertheless, the Taiyang channel is not only susceptible to invasion by severe cold in winter; cold pathogens in all four seasons can invade it. If upon invasion the body is indeed cold, the pulse is indeed tight, and symptoms are complete, then Mahuang may be used regardless of the season. If upon invasion the cold is not severe, and the pulse is not notably tight, even if symptoms are present, Mahuang may be omitted even in winter. Furthermore, for individuals who are exhausted from labor or whose original Qi is depleted after illness, if they accidentally contract a cold pathogen and present with a tight pulse but weak strength, one must apply flexible treatment strategies rather than rigidly adhering to the use of Mahuang. This is because Mahuang possesses a fierce and potent nature; while it easily attacks pathogens, it readily damages healthy Qi. A single misapplication can lead to unpredictable complications; how can one not be cautious?
Note: Mahuang Tang is the primary medicine for the Taiyang channel. I emphasize caution repeatedly because if the timing, the channel, or the patient's constitution does not match the indication, harm is rarely avoided. Please do not experiment lightly; this would be a great fortune for the world.
Clinical Cases:
A friend, after accumulating fatigue, contracted cold and developed fever. The physician failed to examine carefully and administered Mahuang Tang. This resulted in red eyes, epistaxis (nosebleed), and blood in the sputum. Subsequently, Xiaochaihu Tang (Minor Bupleurum Decoction) was given, leading to a dry tongue lacking fluids. Upon my examination, the pulse was deficient, rapid, and weak, indicating a pattern of fatigue combined with Yin deficiency. Misadministration of hot-natured drugs inevitably caused bleeding and exhaustion of fluids. After administering Dihuang Tang (Rehmannia Decoction) for three doses, the bleeding stopped, but mental clarity had not returned. I prescribed Shengmai San (Generate the Pulse Powder) and Guipi Tang (Restore the Spleen Decoction) with Baizhu (Atractylodis Rhizoma) removed. Although the spirit settled, the tongue still failed to produce fluids. I stated: "The Kidney governs the five fluids, and the Lung is the source of production and transformation." Why did both nourishing Yin and tonifying Qi fail? After deep contemplation, I realized that Mahuang's nature does not retain inward; despite administration, no sweat occurred. It merely injured Yin, causing bleeding from the mouth and nose, while the medicinal properties were never vented outward. Consequently, fluid metabolism remained stagnant. I continued using Shengmai San to secure the root, and added Gegen (Puerariae Radix) and Chenpi (Citri Reticulatae Pericarpium) to guide the Qi. Thus, mild sweating ensued, and fluids finally appeared on the tongue. The patient recovered later with Guipi Tang and Liuwei Wan (Six-Ingredient Rehmannia Pill).
A physician, arrogant by nature, contracted cold in autumn. He self-administered two doses of Mahuang Tang. This led to red eyes, cracked lips, and disregard for propriety (exposing nakedness). Ultimately, he developed a complex disorder (Huai Zheng).
A herbal merchant caught a wind-cold. Believing himself knowledgeable about medicines, he ingested five qian of Mahuang. He suffered continuous hematemesis (vomiting blood) and died. For these two cases, even the administration of Huanglian Jiedu Tang (Coptis Decoction to Relieve Toxicity) and Xijiao Dihuang Tang (Rhinoceros Horn and Rehmannia Decoction) could not save them. This is truly terrifying.
Mahuang Tang Formula:
Mahuang (Ephedrae Herba, 2 qian)
Guizhi (Cinnamomi Ramulus, 1 qian)
Gancao (Glycyrrhizae Radix et Rhizoma, 0.5 qian)
Xingren (Armeniacae Semen Amarum, 8 grains)
Decoct with water, adding fresh ginger and jujube.
Jiwei Qianghuo Tang Formula:
Qianghuo (Notopterygii Rhizoma et Radix)
Fangfeng (Saposhnikoviae Radix)
Cangzhu (Atractylodis Rhizoma) (each 1 qian)
Gancao (Glycyrrhizae Radix et Rhizoma)
Baizhi (Angelicae Dahuricae Radix)
Chuanxiong (Ligustici Chuanxiong Rhizoma)
Shengdihuang (Rehmanniae Radix)
Huangqin (Scutellariae Radix) (each 1.5 qian)
Xixin (Asari Radix et Rhizoma) (0.7 qian)
Decoct with water, adding fresh ginger and jujube.