气味苦寒，有毒。主治伤寒寒热，热发温疟，鬼毒，胸中痰结，吐逆。
（常山又名恒山，出益州及汉中，今汴西、淮浙、湖南州郡皆有。生山谷间，茎高三四
尺，
圆而有节，其叶似茗，两两相对，二月作白花，青萼，五月结实青圆。常山者，根之名也。
状似荆根，细实而黄者，谓之鸡骨常山，用之最胜，其苗别名蜀漆。古时根苗皆入药用，今
时但用常山，不用蜀漆，犹之赤箭、天麻，但用天麻，无有用赤箭者，盖以其苗不复远市耳
。）
恒山，北岳也。后以汉文帝讳恒，遂改名常山。此草名常山，亦名恒山。李时珍疑其始
出于
常山，故得此名，余以此思常山之草，盖禀西北金水之化而气出于东南。主治伤寒之寒热者
，从西北之阴而外出于阳也。热发温疟者，乃先发热之温疟。温疟病藏于肾，常山从西北而
出于东南，则温疟可治也。神气乃浮，则鬼毒自散。阳气外行，则胸中痰结自消，痰结消而
吐逆亦平矣。
愚按∶伤寒寒热，言伤寒之病，先寒后热也。热发温疟，言温疟之病，先热发而后寒也。
言
不尽意，以意会之。
《阴阳离合论》云∶圣人南面而立，前曰广明，后曰太冲，太冲之地，名曰少阴，少阴之上
，名曰太阳，是太阳之气根于少阴，主于肤表。常山从少阴而达太阳之气以外出，所谓因于
寒，欲如运枢，起居如惊，神气乃浮者，是也。
[Flavor and Nature] Bitter, cold, toxic.
[Indications] Treats chills and fever caused by Cold Damage (Shanghan), warm-type malaria (Wen Nue), ghost-toxic pathogens, phlegm accumulation in the chest, and vomiting with reflux.
(Changshan is also known as Hengshan. It originates from Yizhou and Hanzhong regions, and is now produced in various prefectures such as Bianxi, Huai-Zhe, and Hunan. It grows in mountain valleys, with stems three to four chi high, round and jointed. Its leaves resemble those of tea plants, growing opposite each other. In the second lunar month, it produces white flowers with green calyces, and bears green, round fruits in the fifth lunar month. "Changshan" refers to the root. The variety resembling the root of Vitex rotundifolia, which is fine, solid, and yellow, is called Jigu Changshan (Chicken Bone Changshan) and possesses the best medicinal efficacy; its aerial parts are alternatively named Shuqi. In ancient times, both roots and aerial parts were used medicinally. Currently, only the root (Changshan) is used, not the aerial part (Shuqi). This is similar to Chijian (Astragali Complanati Radix) and Tianma (Gastrodiae Rhizoma); only Tianma is used, while Chijian is rarely used, likely because the aerial parts are no longer traded over long distances.)
Hengshan is the Northern Great Mountain. Later, due to the naming taboo of Emperor Wen of Han (Liu Heng), it was renamed Changshan. This herb is named Changshan, also referred to as Hengshan. Li Shizhen suspected that it originally originated from Changshan, hence the name. I reason that the herbs of Changshan have absorbed the transformation of Metal and Water from the Northwest, while their Qi emerges from the Southeast. Its ability to treat chills and fever in Cold Damage lies in its action of moving from the Yin aspect of the Northwest outward to the Yang aspect. Regarding warm-type malaria characterized by initial fever, this condition involves pathogens stored in the Kidney. Since Changshan's Qi moves from the Northwest to the Southeast, it can treat warm-type malaria. When the Shen-Qi (Spiritual Qi) floats upward, ghost-toxic pathogens naturally dissipate. As Yang Qi moves outward, phlegm accumulation in the chest naturally resolves; once the phlegm accumulation clears, vomiting and reflux subside.
Commentary: "Chills and fever in Cold Damage" refers to the symptom pattern of Cold Damage where chills precede fever. "Initial fever in warm-type malaria" refers to the symptom pattern of warm-type malaria where fever precedes chills. Words cannot fully convey meaning; one must comprehend through intent.
The *Treatise on the Separation and Union of Yin and Yang* states: "When the sage stands facing south, the front is called Guangming, and the back is called Taichong. The region of Taichong is named Shaoyin; above Shaoyin is named Taiyang. This indicates that the Qi of Taiyang is rooted in Shaoyin and governs the skin surface." Changshan can reach the Qi of Taiyang from Shaoyin and move outward to the body surface. This corresponds to the principle stated in the classics: "Due to cold, [the Qi] desires to move like a pivot; if daily life is disturbed like a startle, the Shen-Qi will float."