味辛甘微苦。气平而温。气薄味浓。降也。入足少阴厥阴经。 肝经气分药。 主治
腰膝痛。补中益精气。坚筋骨强志。除阴下痒湿。小便余 。治肾劳腰脊挛。脚中酸疼。不
欲践地。（此阴不得阳以运者）除肾冷 。润肝燥。补肝经风虚。 能使筋骨相着。（东垣）
虽温而不助火。（士材） 色紫而润。气温平而和阳。味辛甘而裕阴。故能由肾而致肝之功
用若此。（濒湖） 肾苦燥。急食辛以润之。肝苦急。急食甘以缓之。杜仲辛甘具足。正能
解肝肾之所苦。而补其不足者。 同牛膝枸杞子续断白胶地黄山药五味子菟丝子黄柏。治肾
虚腰痛。及下部软弱无力。 胎孕三四月惯堕者。于两月前。以杜仲八两。糯米煎汤浸透。
炒去丝。续断二两。酒浸焙干。为末。以山药末五六两糊丸。梧子大。空心米饮下。 少年
新娶得脚软病疼甚。作香港脚治不效。用杜仲一两。每半酒半水煎服。取愈。
〔论〕 杜仲味先辛。次甘。又次苦。甘不敌辛。而苦则微甚。以辛始而以苦终。是苦
乃辛甘归宿之地。而引辛甘致其用者。固在苦也。苦属火。苦所就下之火。即元气。兹味由
辛甘而苦。是其归于中五之冲气者。皆降而浓育乎阴中之阳也。即其色紫。非下就相火之一
证乎。夫三焦元气。上下际蟠。（水中有火。乃肾中元气。而三焦布之。） 兹何以独致其用
于下。盖中土之甘。化归于肾。而天气之辛化。又因中土而归之。则所谓益元阳。致津液者。
其
总之。此味功用。全以元气为本。（身半以下。腰膝与脚。皆借此阴中元阳以为张弛之主。
至于疗堕胎。尤以化为主。不徒恃形器之相维也。） 本经所谓益精气强志。皆不离元气而
言。但于阴中生阳。即于阳中含阴。非偏于阳者。（非偏于补阳。故兹味以益精气为主。精
气益则筋骨自坚。）经故谓其气平。李氏亦云温而不助火也。抑三焦元气即肾气。乃又言其
为肝经气分药者。以肝本肾为化原。而还为肾畅其化育之用。试参东垣能使筋骨相着一语。
则可见肝之化原在肾。而肾之资益在肝。此味由肾益肝。即由肝资肾。故得筋骨相着。肝之
借以致其气化者此耳。非谓其更入肝也。（能补肾中元气。即是肝经气分药。即是能补风虚
润肝燥药。肝燥者何。元阳虚而风木之真气不达。故燥急也。）藉非本于三焦之元气。阴中
生阳。阳中含阴。其能使风虚肝燥胥以受益乎。至如阴下痒湿。小便余沥。皆阳气之不周于
阴也。虽贵其脂润。而取用在皮。亦可以思矣。审此则凡阴虚以为腰痛者。犹当酌而施之矣
。甄权疗肾冷 腰痛。日华子治肾劳腰脊挛。夫冷与劳。皆属肾气之虚。肾中元阳虚。即有
腰痛脊挛之证。亦即有阳虚而病于风之证。盖阳虚而并。不能达阴。故病于风。即海藏所谓
风虚也。又所谓肝燥者。即阳不得致于肝。而阴亦不得随之以至肝也。阴阳合一之义。可于
兹味见一班。惟由益肾以致肝。比于石枣（即山萸肉）之先温肝以助肾者有异耳。
肾虚火炽者。不宜用。即用当与知柏同入。（仲淳）
〔修治〕削去粗皮。每一斤。用酥一两。蜜三两。和涂火炙。以尽为度。一法。用酒炒
断丝。以渐取屑。方不焦。 浓而实者。能强筋骨。用面炒去丝。童便浸七日。新瓦焙干为
末。
杜仲味辛、甘，微苦。气平而温。气薄味浓，性主沉降。入足少阴肾经和足厥阴肝经。是作用于肝经气分的药物。
主治腰膝疼痛。补益中气，增益精气。坚固筋骨，增强意志。消除外阴瘙痒潮湿。治疗小便淋漓不尽。治疗肾劳引起的腰脊拘挛。脚部酸痛，不想踩地。（这是由于阴精得不到阳气的运化所致）消除肾脏寒冷。（李东垣认为能）使筋骨紧密结合。（马士材认为）虽然性温但不助长火邪。（李时珍认为）其色紫且润泽，气温平能和缓阳气，味辛甘能滋养阴液。所以能产生从补肾到养肝的功效。（张景岳认为）肾怕干燥，急需食用辛味药来润燥；肝怕拘急，急需食用甘味药来缓和。杜仲兼具辛甘之味，正好能解除肝肾的困苦，并补充其不足。
与牛膝、枸杞子、续断、白胶（阿胶）、地黄、山药、五味子、菟丝子、黄柏同用，可治疗肾虚腰痛及下部软弱无力。对于怀孕三四月习惯性流产者，在孕前两个月，用杜仲八两，糯米煎汤浸透，炒去丝，加续断二两，酒浸焙干，研为细末，再用山药末五六两制成糊丸，如梧桐子大，空腹米饮送服。少年新婚得脚软病，疼痛剧烈，按香港脚（痛风/下肢肿痛）治疗无效，用杜仲一两，半酒半水煎服，痊愈。
〔论〕 杜仲味先辛，次甘，又次苦。甘不敌辛，而苦则微弱。以辛始而以苦终，说明苦是辛甘归宿之地，而引导辛甘发挥作用的，关键在于苦。苦属火，苦所趋向的下行之火，即是元气。此药由辛甘转为苦，是其归于中土冲和之气，都是沉降而浓厚地孕育阴中之阳。从其色紫来看，不也是趋向相火的一个证据吗？三焦元气，上下盘结。（水中有火，即肾中元气，由三焦布散全身。）为何此药独独在下部发挥作用？大概是因为中土的甘味化归于肾，而天气的辛味又因中土而归肾，所谓益元阳、致津液的作用，总归于此。此药的功用，全以元气为本。（身体下半部分的腰膝与脚，都借此阴中的元阳作为张弛的主宰。至于治疗堕胎，尤其以气化为主，不仅仅依靠形器的维系。）《本经》所说的益精气强志，都不离开元气而言。只是在阴中生阳，即在阳中含阴，并非偏于阳。（并非偏于补阳，所以此药以益精气为主，精气益则筋骨自然坚固。）因此说它气平，李氏也说温而不助火。况且三焦元气即肾气，却又说它是肝经气分药，是因为肝的本源在于肾，而反过来帮助肾畅达其化育的作用。参看李东垣“能使筋骨相着”这句话，可见肝的化原在肾，而肾的资助在肝。此药由肾益肝，即由肝资肾，所以能得到筋骨相着的效果。这是肝借以发挥气化作用的原因罢了。并不是说它更直接入肝。（能补肾中元气，就是肝经气分药，就是能补风虚、润肝燥的药。什么是肝燥？元阳虚而风木的真气不达，所以燥急。）如果不是基于三焦的元气，阴中生阳，阳中含阴，难道能让风虚肝燥都受益吗？至于外阴瘙痒潮湿，小便余沥，都是阳气不能周流于阴的表现。虽然珍贵其脂润，但取用在皮，也可以深思了。明了这一点，那么凡是阴虚导致的腰痛，还应当斟酌施用。甄权治疗肾冷腰痛，日华子治疗肾劳腰脊拘挛。冷与劳，都属于肾气虚。肾中元阳虚，就有腰痛脊挛的证候，也就是有阳虚而受风的证候。因为阳虚而合并，不能达于阴，所以病于风，即海藏所说风虚。又说肝燥，即阳气不能到达肝，而阴也不能随之到达肝。阴阳合一的道理，可以从这味药见一斑。只是由益肾以致肝，与石枣（即山萸肉）先温肝以助肾有所不同。
肾虚火炽者，不宜使用。即使使用也应当与知母、黄柏同入。（陈实功认为）
〔修治〕削去粗皮。每一斤，用酥一两，蜜三两，调和涂在火上炙烤，直到烤尽为止。另一种方法，用酒炒断丝，慢慢取屑，这样才不会焦。质地浓密坚实的，能强筋骨。用面炒去丝，童便浸泡七日，新瓦焙干研为细末。
Du Zhong (Eucommiae Cortex) tastes pungent, sweet, and slightly bitter. Its nature is neutral and warm. Its qi is thin while its flavor is dense, and it has a descending property. It enters the Foot-Shaoyin Kidney Meridian and the Foot-Jueyin Liver Meridian. It is a herb that acts on the Qi level of the Liver Meridian.
It mainly treats pain in the lower back and knees. It tonifies the Middle Jiao, benefits Essence and Qi, strengthens sinews and bones, and fortifies the will. It eliminates itching and dampness in the genital area. It treats urinary dribbling. It treats kidney labor causing spasms of the lower back and spine, soreness and pain in the feet, and an unwillingness to tread on the ground. (This occurs when Yin fails to be transported by Yang.) It eliminates cold in the kidney. (Li Dongyuan stated it can make sinews and bones adhere closely together.) (Ma Shicai stated that although it is warm, it does not aid fire.) Its color is purple and lustrous; its temperature is neutral and harmonizes Yang; its pungent and sweet flavors enrich Yin. Therefore, it can achieve effects from benefiting the Kidney to nourishing the Liver. (Li Shizhen noted this.) The Kidney dislikes dryness and urgently needs pungent foods to moisten it; the Liver dislikes tension and urgently needs sweet foods to relax it. Du Zhong possesses both pungent and sweet flavors, perfectly resolving the distress of the Liver and Kidney and supplementing their deficiencies.
When used with Niuxi (Achyranthis Bidentatae Radix), Gouqizi (Lycii Fructus), Xuduan (Dipsaci Radix), Baijiao (Ejiao, Donkey-hide Gelatin), Dihuang (Rehmanniae Radix), Shanyao (Dioscoreae Rhizoma), Wuweizi (Schisandrae Fructus), Tusizi (Cuscutae Semen), and Huangbai (Phellodendri Cortex), it treats lumbar pain due to Kidney deficiency and weakness in the lower body. For those prone to habitual miscarriage at three or four months of pregnancy, two months prior to conception, take eight taels of Du Zhong, soak it thoroughly in decoction made from glutinous rice, stir-fry to remove silk fibers, add two taels of Xuduan soaked in wine and dried over low heat, grind into powder, mix with five or six taels of Shanyao powder to form pills the size of wutong seeds, and swallow with rice water on an empty stomach. A young man who recently married suffered from severe leg weakness and pain. Treatment for Hongxiangjiao (Gout/Lower limb swelling and pain) was ineffective. Using one tael of Du Zhong, decocted with half wine and half water, he recovered.
[Discussion] Du Zhong's taste begins with pungency, followed by sweetness, and finally bitterness. Sweetness does not overpower pungency, while bitterness is slight. Beginning with pungency and ending with bitterness indicates that bitterness is the destination of pungency and sweetness, and it is bitterness that guides their efficacy. Bitterness belongs to Fire; the downward-moving fire associated with bitterness is Yuan Qi (Original Qi). This herb transitions from pungent and sweet to bitter, returning to the central Earth's harmonious Qi, thereby sinking and densely nurturing Yang within Yin. Its purple color is also evidence of its affinity with Ministerial Fire. The Yuan Qi of the Sanjiao (Triple Burner) coils up and down throughout the body. (Fire within Water refers to the Yuan Qi of the Kidney, distributed by the Sanjiao.) Why does this herb exert its effect primarily in the lower part? Presumably because the sweetness of Central Earth transforms and returns to the Kidney, and the pungency of Heaven's Qi, via Central Earth, also returns to the Kidney. Thus, the functions of benefiting Yuan Yang and generating fluids converge here. The efficacy of this herb relies entirely on Yuan Qi as its foundation. (The lower half of the body, including the waist, knees, and feet, relies on the Yuan Yang within Yin as the master of tension and relaxation. Regarding treating miscarriage, it relies primarily on Qi transformation, not merely on physical support.) The *Shennong Bencao Jing* states it benefits Essence and Qi and strengthens the will, all referring to Yuan Qi. It generates Yang within Yin and contains Yin within Yang; it is not biased toward Yang alone. (It is not biased toward tonifying Yang, so this herb focuses on benefiting Essence and Qi; when Essence and Qi are benefited, sinews and bones naturally strengthen.) Hence, it is said to have a neutral nature, and Li Shi-zhen also noted it is warm without aiding fire. Furthermore, since the Yuan Qi of the Sanjiao is the Qi of the Kidney, why is it described as acting on the Qi level of the Liver Meridian? Because the Liver originates from the Kidney, and conversely helps the Kidney facilitate its generative functions. Considering Li Dongyuan's statement that it "makes sinews and bones adhere," we see that the origin of Liver transformation lies in the Kidney, and the Kidney's supplementation comes from the Liver. This herb benefits the Liver through the Kidney, and thus the Kidney is supported by the Liver, resulting in adherent sinews and bones. This is how the Liver utilizes Qi transformation. It does not mean it directly enters the Liver meridian in a separate sense. (To benefit the Yuan Qi of the Kidney is to act on the Qi level of the Liver Meridian, meaning it is a herb that tonifies Wind-Deficiency and moistens Liver Dryness. What is Liver Dryness? It is when Yuan Yang is deficient and the true Qi of Wind-Wood fails to reach, causing dryness and tension.) If it were not based on the Yuan Qi of the Sanjiao, generating Yang within Yin and containing Yin within Yang, could it benefit Wind-Deficiency and Liver Dryness? As for itching and dampness in the genital area and urinary dribbling, these are manifestations of Yang failing to circulate fully into Yin. Although its lipid richness is valued, its utility lies in the bark, which invites deep thought. Understanding this, for lumbar pain caused by Yin deficiency, one should still exercise discretion in its use. Zhen Quan treated lumbar pain due to Kidney Cold; Ri Huazi treated lumbar and spinal spasms due to Kidney Labor. Cold and Labor both belong to Kidney Qi deficiency. Deficiency of Yuan Yang in the Kidney leads to symptoms of lumbar pain and spinal spasms, which are also signs of Wind pathology due to Yang deficiency. When Yang is deficient and combined, it cannot reach Yin, leading to Wind pathology, known as Haizang's "Wind-Deficiency." Also, "Liver Dryness" means Yang cannot reach the Liver, nor can Yin follow it. The principle of the unity of Yin and Yang can be glimpsed in this herb. However, benefiting the Liver through the Kidney differs from Shizao (Corni Fructus), which first warms the Liver to assist the Kidney.
It is not suitable for cases of Kidney deficiency with blazing Fire. If used, it should be combined with Zhimu (Anemarrhenae Rhizoma) and Huangbai (Phellodendri Cortex). (Chen Shigong stated this.)
[Processing] Scrape off the rough bark. For every jin (500g), mix with one liang of Su (Butyrum) and three liang of Mi (Honey), apply evenly, and roast over fire until completely processed. Another method: stir-fry with wine to break the silk fibers, then gradually crush into powder to avoid burning. Those that are dense and solid can strengthen sinews and bones. Stir-fry with flour to remove silk fibers, soak in Tongbian (Child's Urine) for seven days, dry on new tile tiles, and grind into powder.