今之治偏枯者多主气虚之说，而习用《医林改错》补阳还五汤。然此方用之有效有不效，更间有服之
即偾事者，其故何也？盖人之肢体运动原脑髓神经为之中枢，而脑髓神经所以能司运动者，实赖脑中血管为
之濡润，胸中大气为之斡旋。乃有时脑中血管充血过度，甚或至于破裂，即可累及脑髓神经，而脑髓神经遂
失其司运动之常职；又或有胸中大气虚损过甚，更或至于下陷，不能斡旋脑髓神经，而脑髓神经亦恒失其司运
动之常职。此二者，一虚一实，同为偏枯之证，而其病因实判若天渊。设或药有误投，必至凶危立见。是以
临此证者，原当细审其脉，且细询其未病之先状况何如。若其脉细弱无力，或时觉呼吸短气，病发之后并无心
热头疼诸证，投以补阳还五汤，恒见效。即不效，亦必不至有何弊病。若其脉洪大有力，或弦硬有力，更
预有头疼眩晕
之病，至病发之时，更觉头疼眩晕益甚，或兼觉心中发热者，此必上升之血过多，致脑中血管充血过甚，隔管
壁泌出血液，或管壁少有罅漏流出若干血液，若其所出之血液，粘滞左边司运动之神经，其右半身即偏枯，若
粘滞右边司运动之神经，其左半身即偏枯。此时若投以拙拟建瓴汤，一二剂后头疼眩晕即愈。继续服
之，更加以化瘀活络之品，肢体亦可渐愈。若不知如此治法，惟确信王勋臣补阳还五之说，于方中重用黄 ，
其上升之血益多，脑中血管必将至破裂不止也，可不慎哉！如以愚言为不然，而前车之鉴固有医案可征也。
邑某君，年过六旬，患偏枯原不甚剧。欲延城中某医治之，不遇。适有在津之老医初归，造门自荐。服
其药后，即昏不知人，迟延半日而卒。后其家人持方质愚，系仿补阳还五汤，重用黄 八钱。知其必系脑
部充血过度以致偏枯也，不然服此等药何以偾事哉？
又尝治直隶王××，其口眼略有歪斜，左半身微有不利，时作头疼，间或眩晕，其脉象洪实，右部尤甚，
知其系脑部充血。问其心中，时觉发热。治以建瓴汤，连服二十余剂全愈。王××愈后甚喜，而转念忽有所
悲，因告愚曰∶“五舍弟从前亦患此证，医者投以参 之剂，竟至不起。向以为病本不治，非用药有所错误，
今观先生所用之方，乃知前方固大谬也。”统观两案及王××之言，则治偏枯者不可轻用补阳还五汤，不
愈昭然哉！而当时之遇此证者，又或以为中风而以羌活、防风诸药发之，亦能助其血益上行，其弊与误用参
者同也。盖此证虽有因兼受外感而得者，然必其外感之热传入阳明，而后激动病根而猝发，是以
虽挟有外感，亦不可投以发表之药也。
当今治疗半身不遂（偏枯）的人，大多主张气虚的说法，因而习惯性地使用《医林改错》中的补阳还五汤。然而，这个方剂使用时有的有效，有的无效，更有甚者服用后反而导致病情恶化甚至危及生命，这是什么原因呢？
原来，人的肢体运动原本由脑髓神经作为中枢控制，而脑髓神经之所以能够主持运动功能，实际上依赖于脑中血管的濡润滋养，以及胸中大气（宗气）的斡旋推动。有时候，脑中血管充血过度，甚至发生破裂，就会累及脑髓神经，致使脑髓神经失去其主持运动的正常职能；又或者，胸中大气虚损过于严重，甚至下陷，无法斡旋推动脑髓神经，那么脑髓神经也常常失去其主持运动的正常职能。这两种情况，一为虚证，一为实证，虽然都表现为半身不遂，但其病因实则天差地别。如果用药有误，必定会立刻出现凶险危急的情况。因此，面对这种病症，原本应当仔细诊察脉象，并且详细询问患者在发病之前的身体状况如何。
如果患者脉象细弱无力，或者时常感觉呼吸短促，发病之后并没有心中发热、头痛等症状，此时投用补阳还五汤，往往能见效。即使不见效，也一定不会产生什么弊病。如果患者脉象洪大有力，或者弦硬有力，并且预先就有头痛眩晕的疾病，到了发病的时候，更觉得头痛眩晕加剧，或者兼有心中发热的感觉，这一定是因为上升的血过多，导致脑中血管充血过甚，血液透过管壁渗出，或者管壁有细微裂缝流出若干血液。如果渗出的血液粘滞了左侧主管运动的神经，右侧半身就会发生半身不遂；如果粘滞了右侧主管运动的神经，左侧半身就会发生半身不遂。
在这个时候，如果投用我建议的建瓴汤，服用一两剂后，头痛眩晕就会痊愈。继续服用，再加上化瘀通络的药物，肢体也可以逐渐恢复。如果不知道这样的治法，只确信王清任（字勋臣）补阳还五汤的理论，在方中重用黄芪，那么上升的血就会更多，脑中血管必将破裂不止，这能不谨慎吗！如果觉得我的话不对，那么前车之鉴确实有医案可以证明。
本县有一位某先生，年龄超过六十岁，患半身不遂原本并不严重。想要请城里的某位医生医治，但医生不在家。恰好有位在天津的老医生刚回来，登门自荐。服用他的药后，病人立刻昏迷不省人事，拖延了半天就去世了。后来他的家人拿着药方来质问我，那方子是仿照补阳还五汤，重用黄芪八钱。我知道他必定是因为脑部充血过度导致的半身不遂，否则服用这种药物怎么会导致病情恶化致死呢？
又曾经治疗直隶的王××，他的口眼略有歪斜，左半身稍微有些不利索，时常头痛，偶尔眩晕，脉象洪实，右部尤其明显，我知道这是脑部充血。问他心里，时常感觉发热。我用建瓴汤治疗，连续服用二十多剂后完全痊愈。王××痊愈后非常高兴，但转念忽然感到悲伤，于是告诉我说：“我的五弟从前也患过这个病，医生给他用了人参等补气药剂，竟然导致死亡。以前我认为这是病根本治不好，不是用药有什么错误，现在看了先生所用的方子，才知道前面的方子确实大错特错。”综合这两个医案以及王××的话，那么治疗半身不遂不可轻易使用补阳还五汤，不是更加明白昭著了吗！而当时遇到这种病症的人，又或许认为是中风而用羌活、防风等药物发散，这也同样会使血益向上行，其弊端与误用人参是一样的。因为这个病症虽然有因为兼受外感而得病的，但必须是外感的热邪传入阳明经，而后激动病根才突然发作，所以即使夹杂有外感，也不可投用发表（解表）的药物。
Currently, those who treat hemiplegia (pian ku) mostly adhere to the theory of Qi deficiency and habitually use Bu Yang Huan Wu Tang from *Yi Lin Gai Cuo*. However, this formula is effective in some cases but ineffective in others, and there are even instances where its administration leads to disaster or death. What is the reason for this?
The movement of human limbs is originally controlled by the brain marrow nerves as the central hub. The ability of these nerves to govern movement actually relies on the nourishment provided by the blood vessels in the brain and the rotation/pivoting action of the Da Qi (Grand Qi / Zong Qi) in the chest. Sometimes, excessive congestion of the blood vessels in the brain, or even their rupture, can affect the brain marrow nerves, causing them to lose their normal function of governing movement. Alternatively, if the Da Qi in the chest is severely deficient or sinks downward, failing to pivot and support the brain marrow nerves, these nerves will also frequently lose their normal function of governing movement. These two conditions, one being deficiency and the other excess, both manifest as hemiplegia, yet their etiological causes are worlds apart. If medication is misapplied, perilous and critical conditions will appear immediately. Therefore, when facing such a condition, one must carefully examine the pulse and inquire in detail about the patient's condition prior to the onset of illness.
If the pulse is fine, weak, and forceless, or if the patient occasionally feels shortness of breath, and after the onset of the disease, there are no symptoms such as heat in the heart or headache, administering Bu Yang Huan Wu Tang often yields results. Even if it is ineffective, it certainly will not cause harm. If the pulse is surging, large, and forceful, or wiry, stiff, and forceful, and the patient has a history of headache and dizziness, which worsen at the time of onset, accompanied by a sensation of heat in the heart, this indicates that excessive ascending blood has caused severe congestion in the brain's blood vessels. Blood may seep through the vessel walls or leak out from minor fissures. If the leaked blood adheres to the nerves on the left side responsible for movement, the right half of the body becomes paralyzed; if it adheres to the nerves on the right side, the left half becomes paralyzed.
At this time, if Jian Ling Tang (Jian Ling Decoction), as I propose, is administered, headache and dizziness will resolve after one or two doses. Continued administration, combined with herbs that resolve stasis and unblock collaterals, will gradually restore limb function. If one does not understand this treatment method and solely believes in Wang Qingren’s (Zixun) theory of Bu Yang Huan Wu Tang, heavily using Huangqi (Astragali Radix) in the formula, the ascending blood will increase further, likely leading to continuous rupture of the brain's blood vessels. Can one be too cautious? If you do not agree with my words, the lessons of the past are evidenced by medical cases.
A gentleman in our county, over sixty years old, suffered from mild hemiplegia. He wished to consult a doctor in the city, but the doctor was unavailable. An elderly physician returning from Tianjin happened to visit and offered his services. After taking the prescribed medicine, the patient fell into a coma and died half a day later. Later, the family brought the prescription to question me. It was modeled after Bu Yang Huan Wu Tang, with Huangqi (Astragali Radix) heavily used at eight qian. I knew he must have suffered from hemiplegia due to excessive cerebral congestion; otherwise, how could such medication lead to disaster and death?
I once treated Wang XX from Zhili, who had slight deviation of the mouth and eyes, slight difficulty in the left half of the body, frequent headaches, and occasional dizziness. His pulse was surging and solid, especially on the right side, indicating cerebral congestion. He reported feeling heat in his heart. I treated him with Jian Ling Tang (Jian Ling Decoction). After more than twenty doses, he was completely cured. Wang XX was very pleased after recovery but then turned sad and told me: "My fifth brother previously suffered from this same condition. The doctor administered tonics containing Renshen (Ginseng Radix), and he passed away. I previously thought the disease was incurable and that the medication was not at fault. Now, seeing the formula you used, I realize the previous prescription was fundamentally wrong." Considering these two cases and Wang XX's words, it is evident that treating hemiplegia requires caution against lightly using Bu Yang Huan Wu Tang. Furthermore, those encountering this condition might mistakenly diagnose it as wind-stroke and use dispersing herbs like Qianghuo (Notopterygii Rhizoma) and Fangfeng (Saposhnikoviae Radix). This would similarly drive blood upward, creating the same detriment as misusing Renshen (Ginseng Radix). Although this condition can sometimes arise from external contraction, it must be that the heat from the external pathogen transmits to the Yangming channel, thereby agitating the root of the disease and causing sudden onset. Therefore, even if accompanied by an external contraction, dispersing (releasing the exterior) medications should not be administered.