气味辛、平，无毒。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。
（参张隐庵）杜仲气味辛平，得金之气味；而其皮黑色而属水，是禀阳明、少阴金水之
精气而为用也。腰为肾府，少阴主之；膝属大筋，阳明主之；杜仲禀少阴、阳明之气，故腰
膝之痛可治也。补中者，补阳明之中土也；益阴者，益少阴之精气也；坚筋骨者，坚阳明所
属之筋，少阴所主之骨也；强志者，肾藏志，肾气得补而壮，气壮而志自强也。阳明燥气下
行，故除阴下湿痒，小便余沥也。久服则水金相生，精气充足，故轻身耐老也。
气味甘、寒，无毒。主伤中，五劳六极，羸瘦，崩中绝脉，补虚益气。（旧
本列为中品，今从《崇原》。）
叶天士曰∶桑皮气寒，禀水气而入肾；味甘无毒，得土味而入脾。中者，中州脾也。脾
为阴气之原，热则中伤，桑皮甘寒，故主伤中。五劳者，五脏劳伤真气也。六极者，六腑之
气虚极也。脏腑俱虚，所以肌肉削而羸瘦也。其主之者，桑皮甘以固脾气而补不足，寒以清
内热而退火邪，邪气退而脾阴充，脾主肌肉，自然肌肉丰而劳极愈矣。崩中者，血脱也；脉
者，血之府；血脱故脉绝不来也。脾统血而为阴气之原，甘能益脾，所以主崩中绝脉也。火
与元气势不两立，气寒清火，味甘益气，气充火退，虚得补而气受益也。
陈修园曰∶今人以补养之药，误认为清肺利水之品，故用多不效。且谓生用大泻肺气，
宜涂蜜炙之。然此药忌火，不可不知。
张隐庵曰∶桑割而复茂，生长之气最盛，故补续之功如此。
[Dou Zhong / Eucommiae Cortex]
Taste: Acrid, Neutral. Toxicity: Non-toxic. Indications: Primarily treats pain in the lower back and knees; tonifies the Middle Jiao (Central Digestive Function), benefits Essence and Qi (Vital Energy); strengthens sinews and bones; fortifies Willpower (Zhi); eliminates dampness and itching in the genital region, and dribbling of urine. Long-term use makes the body light and resistant to aging.
(Referencing Zhang Yin'an): Dou Zhong has an acrid and neutral taste, inheriting the properties of Metal; its bark is black and belongs to Water. Thus, it acts by inheriting the Essence and Qi of Metal and Water from the Yangming and Shaoyin channels. The lower back is the mansion of the Kidney, governed by Shaoyin; the knee belongs to the large sinews, governed by Yangming. Since Dou Zhong inherits the Qi of Shaoyin and Yangming, it can treat pain in the lower back and knees. "Tonifying the Middle" refers to tonifying the Central Earth of the Yangming channel; "Benefiting Yin" refers to benefiting the Essence and Qi of the Shaoyin channel; "Strengthening Sinews and Bones" refers to strengthening the sinews belonging to Yangming and the bones governed by Shaoyin; "Fortifying Willpower" occurs because the Kidney stores Willpower (Zhi); when Kidney Qi is tonified and becomes robust, strong Qi leads to a strong Will. The dry Qi of Yangming descends, thus eliminating dampness and itching in the genital region and urinary dribbling. Long-term use generates Metal and Water mutually, ensuring sufficient Essence and Qi, hence making the body light and resisting aging.
[Sang Gen Bai Pi / Mori Radicis Cortex]
Taste: Sweet, Cold. Toxicity: Non-toxic. Indications: Primarily treats internal injury, Wu Lao Liu Ji (Five Exhaustions and Six Extremes), emaciation, Bing Zhong (Metrorrhagia/Menorrhagia), and Jue Mai (Absence of Pulse); tonifies deficiency and benefits Qi. (Old editions classified this as a Middle-grade herb; now following *Chong Yuan*.)
Ye Tianshi said: Sang Pi (Morus Bark) has a cold nature, inheriting Water Qi to enter the Kidney; it tastes sweet and non-toxic, obtaining the flavor of Earth to enter the Spleen. "Middle" refers to the Middle Jiao Spleen. The Spleen is the source of Yin Qi; heat injures the Middle, so Sang Pi, being sweet and cold, primarily treats injury to the Middle. "Wu Lao" (Five Exhaustions) refers to the damage of True Qi due to labor of the Five Zang Organs. "Liu Ji" (Six Extremes) refers to the extreme deficiency of Qi in the Six Fu Organs. When both Zang and Fu are deficient, muscles waste away leading to emaciation. Sang Pi treats these conditions because its sweetness consolidates Spleen Qi to supplement insufficiency, and its coldness clears internal heat to retreat Fire Pathogens. As pathogens retreat, Spleen Yin fills; since the Spleen governs muscles, muscles naturally become plump, and the condition of extreme exhaustion heals. "Bing Zhong" refers to Blood depletion; "Jue Mai" refers to the vessel of Blood being exhausted; blood depletion causes the pulse to cease. The Spleen controls Blood and is the source of Yin Qi; sweetness benefits the Spleen, thus treating Bing Zhong and Jue Mai. Fire and Original Qi cannot coexist; Sang Pi's coldness clears Fire, and its sweetness benefits Qi. When Qi is full and Fire retreats, deficiency is supplemented and Original Qi benefits.
Chen Xiuyuan said: Nowadays, people mistakenly regard nourishing herbs as agents for clearing Lung Heat and promoting urination, hence frequent use yields no effect. It is also claimed that raw use greatly drains Lung Qi, and honey-fried preparation is preferred. However, one must know that this herb fears fire.
Zhang Yin'an said: The mulberry tree grows lush again after bark cutting, possessing the most vigorous growth Qi, thus demonstrating such significant功效 (efficacy) in replenishing and continuing vitality.