随经者引经必要之药也。引者导引也。引领也。如将之用兵。不识其路。纵兵强将勇。不能取胜。
如贼人无抵。脚不能入其巢穴。叩之箱篑此理也。故用引经药。不可不知。太阳经疮疽生于巅顶之上。
必用羌活 本麻黄。在下黄柏。少阳经耳前上用升麻柴胡。下用柴胡连翘。阳明经面上用葛根白芷黄
芩。下用花粉。太阴经中府云门尺泽上用条芩连翘。下则箕门血
海用苍术防己。少阴经少冲少海。上用细辛。下涌泉照海用知母。厥阴经中冲内泽。上用川芎菖蒲。
下太敦曲泉。柴胡之类。上则言其手经。下则言其足经。当察其此。
经云。汗之则疮已。言疮之邪自外而入。脉必浮数而实。在表故当汗之。邪从汗出。毒自消散。
又恐邪之入里。即内托之意也。如内之外者。因七情所得。脉必沉数而实。当先疏其内。以绝其源。
不令外出是也。不内外因者。是跌仆打压。火烧汤烫等疮。宜和其荣卫。调其饮食。适其寒温。此治
疮之大要三法。不可不知也。
夫疮之始生。有表复有里。表里相兼。当诊其脉。浮沉之间。别其表里之虚实。有表多而里少。
有里多而表少。以防风通圣散千金漏芦汤内当消息。表里多少而药亦随之表里多少。加减得宜。可为
上工也已矣。
痈疽发背皆营气不从。逆于肉理之所生。既成之后。 肿痛甚。五七日内或一头从上开发。或两头开
阔上下侵展不住。帝曰。何气使然。岐伯曰。不善于调养。乃七情之扰。房劳之变。秽气所撞。恶气
所袭。皆令开而不住。当以内托大补之剂。内加白蔹白芨等药服之。外以收敛之药敷贴。淋 竟不开
矣。医当鉴之。
所谓“引经药”，就是引导药物直达病所的必需之药。“引”即导引、引领之意。这就像将领用兵一样，如果不熟悉地形道路，即使士兵强壮、将领英勇，也无法取得胜利；这就好比贼人没有路径可走，双脚无法进入巢穴，敲击箱笼也进不去，这是同样的道理。因此，使用引经药是不可不知的。
太阳经发生的疮疽，生于头顶之上，必须使用羌活、藁本、麻黄；若在下部则用黄柏。少阳经发生在耳前上部，用升麻、柴胡；下部用柴胡、连翘。阳明经发生在面部上部，用葛根、白芷、黄芩；下部用天花粉。太阴经发生在上部的中府、云门、尺泽穴处，用条芩（黄芩）、连翘；在下部则用箕门、血海穴处，用苍术、防己。少阴经发生在上部的少冲、少海穴处，用细辛；在下部涌泉、照海穴处用知母。厥阴经发生在上部的中冲、内关（原文作内泽，疑为内关或内庭之误，此处依原文保留内泽或按语境理解为内侧穴位）、太冲、曲泉穴处，上部用川芎、石菖蒲；下部用柴胡之类。上部所言多指手经，下部所言多指足经，应当仔细考察这一点。
经文说：“发汗则疮愈。”意思是疮疡的邪气从外部侵入，脉象必然浮数而实，病位在表，所以应当用发汗法治疗。邪气随汗而出，毒自然消散。又担心邪气深入体内，这时就用“内托”的意思。如果是因内部因素（如七情所伤）导致的疮疡，脉象必然沉数而实，应当先疏通内部，以断绝病源，不让邪气外发，这就是不内外因中的情况。至于不内外因，是指跌打损伤、挤压、火烧、烫伤等造成的疮疡，适宜调和营卫，调理饮食，适应寒温变化。这是治疗疮疡的三大主要法则，不可不知道。
疮疡刚开始生成时，有在表的，也有在里的，往往是表里兼夹。应当诊察脉象，在浮沉之间，辨别表里证的虚实。有的表证多而里证少，有的里证多而表证少。在使用防风通圣散或千金漏芦汤时，应当斟酌病情，根据表里证的多少来增减药物，加减得当，就可以称为高明的医生了。
痈疽发背都是因为营气运行不畅，逆乱于肌肉纹理之间所产生的。形成之后，肿痛非常剧烈。在五到七天内，或者一个头从上方破溃扩散，或者两个头开阔，上下蔓延不止。黄帝问：这是什么气使然？岐伯答：是因为不善于调养，受到七情的扰乱，房劳过度，以及秽气撞击、恶气侵袭，都导致疮口开而不合。应当使用内托大补的药剂，内部加入白蔹、白及等药物服用，外部用收敛的药物敷贴，淋洗后疮口就会闭合。医生应当以此为鉴。
The term "channel-guiding herbs" refers to the essential medicinal ingredients that guide other drugs directly to the affected meridian. "Guiding" implies leading or directing. This is analogous to a general commanding troops: if one does not know the terrain and roads, even with strong soldiers and brave generals, victory cannot be achieved. It is like thieves having no path to enter their lair; no matter how much they knock on chests or baskets, they cannot get in. The principle is the same. Therefore, it is indispensable to understand the use of channel-guiding herbs.
For sores and carbuncles occurring in the Taiyang Channel (Taiyang Meridian), which manifest on the vertex of the head, Qianghuo (Notopterygii Rhizoma et Radix), Gaoben (Ligustici Rhizoma et Radix), and Mahuang (Ephedrae Herba) must be used; if located in the lower part, Huangbai (Phellodendri Cortex) is used. For the Shaoyang Channel (Shaoyang Meridian), when occurring above the ear, Shengma (Cimicifugae Rhizoma) and Chaihu (Bupleuri Radix) are used; when below, Chaihu (Bupleuri Radix) and Lianqiao (Forsythiae Fructus) are used. For the Yangming Channel (Yangming Meridian), when occurring on the upper face, Gegen (Puerariae Lobatae Radix), Baizhi (Angelicae Dahuricae Radix), and Huangqin (Scutellariae Radix) are used; when below, Huafen (Trichosanthis Radix) is used. For the Taiyin Channel (Taiyin Meridian), when occurring at the upper points Zhongfu (LU-1), Yunmen (LU-2), and Chize (LU-5), Tiaohuangqin (Scutellariae Radix) and Lianqiao (Forsythiae Fructus) are used; when below at Jimen (SP-11) and Xuehai (SP-10), Cangzhu (Atractylodis Rhizoma) and Fangji (Stephaniae Tetrandrae Radix) are used. For the Shaoyin Channel (Shaoyin Meridian), when occurring at the upper points Shaochong (HT-9) and Shaohai (HT-3), Xixin (Asari Radix et Rhizoma) is used; when below at Yongquan (KI-1) and Zhaohai (KI-6), Zhimu (Anemarrhenae Rhizoma) is used. For the Jueyin Channel (Jueyin Meridian), when occurring at the upper points Zhongchong (PC-9) and Neiguan (PC-6, text says Neize), and below at Taichong (LR-3) and Ququan (LR-8), Chuanxiong (Ligustici Chuanxiong Rhizoma) and Changpu (Acori Tatarinowii Rhizoma) are used for the upper part, and herbs like Chaihu (Bupleuri Radix) for the lower part. Generally, references to the upper part pertain to the Hand Channels, while references to the lower part pertain to the Foot Channels; this distinction must be carefully observed.
The classic states, "Sweating will cure the sore." This means that since the pathogenic factor of the sore enters from the exterior, the pulse will necessarily be floating, rapid, and full. Since the disease is in the exterior, sweating therapy should be employed. As the pathogen exits through sweat, the toxicity naturally dissipates. However, there is also concern about the pathogen entering the interior; in such cases, the principle of "internal support" (Neituo) is applied. If the sore arises from internal factors (such as emotional disturbances), the pulse will necessarily be deep, rapid, and full. One should first regulate the interior to cut off the source, preventing the pathogen from emerging outward. Regarding non-internal and non-external causes, these refer to sores caused by falls, crushing, burns, scalds, etc. It is appropriate to harmonize Ying and Wei (Nutritive and Defensive Qi), regulate diet, and adapt to cold and warmth. These three methods constitute the major principles for treating sores and must be known.
When a sore first begins, it may involve the exterior, the interior, or both simultaneously. One must diagnose the pulse, distinguishing between superficial (floating) and deep (sinking) qualities to differentiate the deficiency and excess of the exterior and interior conditions. There may be more exterior involvement than interior, or more interior than exterior. When using formulas such as Fangfeng Tongsheng San (Saposhnikoviae and Peucedani Powder to Unblock the Intestines) or Qianjin Loulu Tang (Thousand-Gold Cistanche Decoction), one must carefully consider the condition. The dosage and combination of herbs should correspond to the degree of exterior and interior involvement. Proper adjustment constitutes the skill of an excellent physician.
Carbuncles on the back arise because Ying Qi (Nutritive Qi) fails to flow smoothly and becomes reversed within the muscle tissues. After formation, swelling and pain are severe. Within five to seven days, either a single head opens and spreads from above, or two heads open wide, spreading continuously up and down. The Yellow Emperor asked, "What qi causes this?" Qibo answered, "It is due to poor self-care, disturbance by the Seven Emotions, changes from sexual exhaustion, collision by foul qi, and assault by malignant qi. All these cause the sore to open and fail to heal." One should administer large tonifying agents for internal support, adding herbs such as Bailian (Belamcandae Rhizoma) and Baiji (Bletillae Rhizoma). Externally, apply astringent herbs as poultices. After washing, the sore will close. Physicians should take this as a warning.