（本经上品）
【气味】辛平，无毒。
【主治】主腰膝痛，补中，益精气，坚筋骨，强志，除阴下痒湿，小便余沥。久服轻身，
耐老。
【核】曰∶出上虞山谷，及上党、汉中。上虞在豫州，虞、虢之虞，非会稽上虞县也。
今出建平、宜都，及商州、成州、峡州，诸山大谷中亦有之。树高数丈，叶似辛夷，又类柘
叶。初生嫩叶可食，谓之棉芽。木皮状似浓朴，拆之白丝相连，江南单呼曰棉。花、实皆苦
涩，亦堪入药。木可作履，以益脚也。修治，削去粗皮。每十六两，用酥一两，蜜三两，和
涂火炙，以尽为度。锉细用。
先人云∶杜仲，从土从中，其色褐，为土克水象，肾之用药也。腰本肾府，湿土为害，
必侵肾水，而腰先受之，据名据色，可以疗也。若象形，能使筋骨相着，又一义矣。
【 】曰∶杜，牝。仲，次，合阴，合耦，合象太阴之始生。自上而下，从外而内者也
。皮络如绵，皮理如革，合至阳沦肤始尽，至阴容平始平也。平则转出为降，降则中实；中
实，遂成入令矣。入则精志益，筋骨强，藏精而起亟矣。何患老之将至，余沥之有；又何患
藏阴之形未充，致奉生者少，转为痿厥，及木用不及之有。既容且平，又何患长夏之土化未
攘，与秋金骤敛，中含润湿之有。
（至阳沦肤始尽，所谓夏三月，此谓蕃莠，至阴容平始平；所谓秋三月，此谓容平。至
阳，即太阳；至阴，即太阴。）
[Shangpin Category of the Classic of Materia Medica]
[Flavor and Nature] Pungent, neutral, non-toxic.
[Indications] Primarily treats pain in the lower back and knees; tonifies the Middle Jiao (Middle Burner); benefits essence and qi; strengthens tendons and bones; fortifies willpower; eliminates itching and dampness in the genital region; and stops dribbling urine after voiding. Long-term consumption lightens the body and delays aging.
[Verification] It is stated: Duzhong grows in the valleys of Shangyu, as well as in Shanggand and Hanzhong. The Shangyu mentioned here is located in Yuzhou, referring to the land of Yu Shun and Guo Shu, not the Shangyu County in Kuaiji Commandery. Currently, it is produced in Jianping, Yidu, Shangzhou, Chengzhou, and Xiazhou, and also grows in major mountain valleys. The tree reaches several zhang in height; its leaves resemble those of Magnolia biondii (Xinyi) and are similar to those of Morus australis (Zheye). The tender young leaves at initial growth are edible and called "Mianya" (Cotton Sprouts). The bark resembles that of Phellodendri Cortex (Houpo); when peeled, white fibrous strands remain connected, and in the Jiangnan region, it is simply called "Mian" (Cotton). Both flowers and fruits are bitter and astringent and can be used as medicine. The wood can be made into footwear to protect the feet. Processing method: Scrape off the rough outer bark. For every 16 liang of the herb, mix with 1 liang of butter (Su) and 3 liang of honey, apply evenly, and roast over fire until the liquid is completely absorbed. Then chop finely for use.
My ancestors said: In the character "Duzhong," 'Du' contains 'Tu' (Earth) and 'Zhong' (Center), and its color is brownish, presenting the image of Earth overcoming Water. Thus, it is a herb for treating Kidney diseases. The waist is the mansion of the Kidney; when Damp-Earth becomes pathogenic, it inevitably invades Kidney Water, causing the waist to suffer first. Based on its name and color, its therapeutic effects can be deduced. If interpreted through form symbolism, it signifies connecting tendons and bones, which is another layer of meaning.
It is discussed: 'Du' implies feminine/yin (Pin); 'Zhong' implies secondary or middle position. Together, they symbolize the convergence of Yin, coupling, and imagery corresponding to the initial generation of Taiyin (Great Yin). Its action moves from top to bottom and from exterior to interior. The vascular network of the bark resembles cotton, while the texture resembles leather. This combines with Zhiyang (Extreme Yang) sinking into the skin to reach completion, and Zhiyin (Extreme Yin) achieving containment and peace to reach balance. When balanced, it transforms into descending movement; descending leads to internal fullness; internal fullness establishes the command of storage/convergence. Storage allows essence and willpower to increase and tendons and bones to strengthen, storing essence and responding promptly to needs. Why worry about approaching old age or residual urinary dribbling? Why worry about insufficiently filled Yin stores leading to weak vitality, resulting in Wei-Jue (flaccidity and cold extremities), or deficiency in Wood function? Since it is both accommodating and balanced, why worry about the persistence of Earth transformation during Late Summer or the sudden constriction of Autumn Metal, which might retain moist-dampness within?
(Zhiyang sinking into the skin to reach completion refers to the three months of summer, described as flourishing vegetation; Zhiyin achieving containment and peace refers to the three months of autumn, described as harvest and stability. Zhiyang is Taiyang; Zhiyin is Taiyin.)