一、用散者，散表证也。观仲景太阳证用麻黄汤，阳明证用升麻葛根汤，少阳证用小柴
胡汤，此散表之准绳也。后世宗之，而复不能用之，在不得其意耳。盖麻黄之气，峻利而勇
。凡太阳经阴邪在表者，寒毒既深，非此不达，故制用此方，非谓太阳经药必须麻黄也。设
以麻黄治阳明、少阳之证，亦寒无不散，第恐性力太过，必反伤其气，岂谓某经某药必不可
移易，亦不过分其轻重耳。故如阳明之升麻、干葛，未有不走太阳、少阳者。少阳之柴胡，
亦未有不入太阳、阳明者。但用散之法，当知性力缓急，及气味寒温之辨，用得其宜，诸经
无不妙也。如麻黄、桂枝，峻散者也；防风、荆芥、紫苏，平散者也；细辛、白芷、生姜，
温散者也；柴胡、干葛、薄荷，凉散者也；羌活、苍术，能走经去湿而散者也；升麻、川芎
，能举陷上行而散者也。第邪浅者，忌峻利之属；气弱者，忌雄悍之属；热多者，忌温燥之
属；寒多者，忌清凉之属。凡热渴烦躁者喜干葛，而呕恶者忌之；寒热往来者宜柴胡，而泄
泻者忌之；寒邪在上者，宜升麻、川芎，而内热炎升者忌之。此性用之宜忌，所当辨也。至
于相配之法，则尤当知要，凡以平兼清，自成凉散；以平兼暖，亦可温经；宜大温者，以热
济热；宜大凉者，以寒济寒。此其运用之权，则毫厘进退，自有伸缩之妙，又何必胶柱刻舟
，以限无穷之病变哉！此无他，在不知仲景之意耳。
1. The use of "San" (dispersing agents) is to disperse exterior syndromes. Observing Zhang Zhongjing, for Taiyang disease (diseases caused by pathogenic factors affecting the Taiyang meridian), he used Mahuang Tang (Ephedra Decoction); for Yangming disease (diseases caused by pathogenic factors affecting the Yangming meridian), he used Shengma Gegen Tang (Cimicifugae and Puerariae Decoction); for Shaoyang disease (diseases caused by pathogenic factors affecting the Shaoyang meridian), he used Xiaochaihu Tang (Minor Bupleurum Decoction). These serve as the standards for dispersing exterior pathogens. Later generations followed this principle but failed to apply it flexibly, due to a lack of understanding of its true intent.
The nature of Mahuang (Ephedrae Herba) is potent, penetrating, and vigorous. In cases where Yin-cold pathogens reside in the exterior of the Taiyang meridian, if the cold toxin has penetrated deeply, only such a potent agent can reach and dispel it. Therefore, this formula was formulated not because Taiyang diseases must exclusively use Mahuang, but rather to address specific conditions. If Mahuang were used to treat Yangming or Shaoyang syndromes, the cold would still be dispersed; however, one must fear that its excessive strength might inadvertently damage Qi. Does this imply that specific herbs are absolutely immutable for specific meridians? No, it merely involves distinguishing the degree of severity. Thus, Shengma (Cimicifugae Rhizoma) and Gegen (Puerariae Radix) used for Yangming disease naturally extend their action to the Taiyang and Shaoyang meridians. Similarly, Chaihu (Bupleuri Radix) used for Shaoyang disease naturally enters the Taiyang and Yangming meridians.
However, when employing dispersing methods, one must understand the urgency or mildness of the herb's nature and distinguish between the flavors and thermal properties (cold/warm). When applied appropriately, treatment across all meridians can yield excellent results. For instance:
- Mahuang (Ephedrae Herba) and Guizhi (Cinnamomi Ramulus) are potent dispersing agents;
- Fangfeng (Saposhnikoviae Radix), Jingjie (Perillae Folium), and Zisu (Perillae Fructus) are mild dispersing agents;
- Xixin (Asari Radix et Rhizoma), Baizhi (Angelicae Dahuricae Radix), and Shengjiang (Zingiberis Rhizoma Recens) are warm dispersing agents;
- Chaihu (Bupleuri Radix), Gegen (Puerariae Radix), and Bohe (Menthae Haplocalycis Herba) are cool dispersing agents;
- Qianghuo (Notopterygii Rhizoma et Radix) and Cangzhu (Atractylodis Rhizoma) disperse pathogens while traversing meridians and removing dampness;
- Shengma (Cimicifugae Rhizoma) and Chuanxiong (Ligustici Chuanxiong Rhizoma) lift sunken Qi upward and disperse pathogens.
Specific contraindications apply:
- For superficial pathogens, avoid potent and penetrating agents;
- For deficient Qi, avoid aggressive and harsh agents;
- For excess heat, avoid warm and drying agents;
- For excess cold, avoid cool and clearing agents.
Regarding specific clinical presentations:
- Patients with heat-induced thirst and restlessness benefit from Gegen (Puerariae Radix), but those with vomiting and nausea should avoid it;
- Patients with alternating chills and fever suit Chaihu (Bupleuri Radix), but those with diarrhea should avoid it;
- Cold pathogens located in the upper jiao suit Shengma (Cimicifugae Rhizoma) and Chuanxiong (Ligustici Chuanxiong Rhizoma), but those with internal heat flaring upward should avoid them.
These indications and contraindications regarding herbal properties must be clearly distinguished. Regarding combination strategies, key principles must be grasped: combining mild agents with cooling agents creates a cooling-dispersing effect; combining mild agents with warming agents can warm the meridians; for strong warming needs, hot-natured herbs support other hot-natured herbs; for strong cooling needs, cold-natured herbs support other cold-natured herbs. The flexibility in application allows for subtle adjustments, possessing the wonder of adaptation. Why then adhere rigidly to fixed rules, thereby limiting the response to infinite variations in pathological changes? This issue stems simply from a failure to understand Zhang Zhongjing’s original intent.