麻黄 细辛 附子
少阴病。始得之。反发热。脉沉者。此汤主之。 按太阳病。发热头痛。其脉当浮。今
反沉
。少阴脉而病似太阳。所以皆谓之反。而治之不同也。均是脉沉。发热。以其有头痛。故为太
阳病。阳
姜生附。亦能发汗。假使里不虚寒。则脉 必浮。而正属太阳麻黄症矣。均是脉沉。发热。
以其无头疼。故名少阴病。阴病当不热。今反发热。则寒邪在表。未传于里。但以皮腠。郁
闭为热。而在里无热。故用麻黄细辛。以发表间之热。附子以温少阴之经。假使寒邪入里。
则外必无热。当见吐利厥逆等症。而正属少阴四逆症矣。由此观之。表邪浮浅。发热之反为
轻。正气衰微。脉沉之反为重。此四逆汤。不为不重于麻黄附子细辛汤也。又可见熟附配麻黄
。发中有补。生附配干姜。补中有发。而仲景之旨微矣。
麻黄 附子 甘草
少阴病。二三日。以此汤微发汗。以无表症。故微发汗也。 按少阴症脉多沉。若沉紧
。不可汗。沉细数。为在里。不可汗。此症必脉沉而喘。是表有寒。而里无邪。故以小辛之药。
微微取汗。按仲景发汗汤剂。各分重轻如麻黄桂枝青龙越婢等汤。各有差等。至少阴发汗二
汤。虽同用麻黄附子。亦有轻重之别。故以加细辛为重。加甘草为轻盖辛散甘缓之义也第一
症以少阴本无热。今发热。故云反也。发热为表邪。当汗。又兼脉沉属阴。当温。故以附子
温经。麻黄发表。而热从汗解。故加细辛是汗剂之重者。第二症。既无里寒可温。又无里热
可下。其所以用麻黄附子之义。则是脉亦沉。方可名曰少阴病。身亦发热。方行发汗药。又得
之二三日。病尚浅比前症稍轻。故不重言脉症。但日微发汗。所以去细辛。加甘草。是汗剂之
轻者。
少阴病，初起时，反而出现发热，脉象沉的，用本方主治。
按语：太阳病，发热头痛，其脉应当浮。现在反而沉。少阴脉而病症类似太阳病，所以都称之为“反”，但治疗方法不同。同样是脉沉、发热，因为伴有头痛，所以诊断为太阳病。生附子配合干姜，也能发汗。假如体内不虚寒，那么脉必然浮，这就正属于太阳病的麻黄汤证了。同样是脉沉、发热，因为没有头痛，所以命名为少阴病。少阴病应当不发热，现在反而发热，说明寒邪在表，尚未传入里部，只是由于皮毛腠理郁闭导致发热，而在里没有热，所以使用麻黄、细辛来发散表间的热，附子来温通少阴经。假如寒邪入里，那么体外必然没有发热，应当出现呕吐、腹泻、四肢厥冷等症状，这就正属于少阴病的四逆汤证了。由此看来，表邪浮浅，发热之“反”为轻；正气衰微，脉沉之“反”为重。因此，四逆汤的重要性并不亚于麻黄附子细辛汤。又可以看出，熟附子配伍麻黄，是在发汗中有补益作用；生附子配伍干姜，是在补益中有发汗作用，而张仲景的旨意是精微深奥的。
少阴病，经过两三天，用本方微微发汗。因为没有明显的表证，所以只是微微发汗。
按语：少阴病的脉象多沉。如果脉沉紧，不可发汗；脉沉细数，说明病在里，不可发汗。此症必定脉沉且喘，这是表有寒邪，而里没有邪气，所以用小辛味的药物，微微取汗。按语：张仲景的发汗汤剂，各自分轻重等级，如麻黄汤、桂枝汤、大青龙汤、越婢汤等，各有差别。至于少阴病发汗的两首方剂，虽然都同用麻黄和附子，也有轻重之别。所以加入细辛为重，加入甘草为轻，这是因为辛味能散、甘味能缓的道理。第一种症状，因为少阴本无热，现在发热，所以说“反”。发热是因为表邪，应当发汗；又兼脉沉属阴，应当温补。所以用附子温经，麻黄发表，而热随汗解。所以加细辛，这是发汗剂中较重的一剂。第二种症状，既然没有里寒可以温补，也没有里热可以攻下。它之所以使用麻黄和附子的意义，则是脉沉才可以称为少阴病，身体发热才可以施行发汗药。又得病二三天，病势尚浅，比前一种症状稍轻，所以不再着重论述脉症，只说微微发汗。因此去掉细辛，加入甘草，这是发汗剂中较轻的一剂。
Ephedrae Herba (Mahuang, 麻黄), Asari Radix et Rhizoma (Xixin, 细辛), Aconiti Lateralis Radix Praeparata (Fuzi, 附子)
Shaoyin disease (Disease of the Shaoyin stage). Upon its onset, there is a counterintuitive fever. If the pulse is deep (Chen), this decoction is the primary treatment.
Commentary: In Taiyang disease (Disease of the Taiyang stage), with fever and headache, the pulse should be floating (Fu). Now it is counterintuitively deep. The pulse belongs to Shaoyin, yet the symptoms resemble Taiyang; hence both are termed "counterintuitive" (Fan), but the treatments differ. Both present with a deep pulse and fever. Because headache is present, it is diagnosed as Taiyang disease. Raw Aconite combined with Dried Ginger can also induce sweating. If the interior were not deficient and cold, the pulse would necessarily be floating, which would correctly belong to the Mahuang Tang syndrome of Taiyang disease. Both present with a deep pulse and fever. Because there is no headache, it is named Shaoyin disease. Shaoyin disease should not involve fever; now there is counterintuitive fever, indicating that cold pathogenic factors are in the exterior and have not transmitted to the interior. It is merely due to the stagnation and closure of the skin and pores causing heat, while there is no heat in the interior. Therefore, Ephedrae Herba and Asari Radix et Rhizoma are used to disperse the heat between the exterior, and Aconiti Lateralis Radix Praeparata is used to warm the Shaoyin meridian. If cold pathogenic factors enter the interior, there will necessarily be no fever on the exterior; instead, symptoms such as vomiting, diarrhea, and cold extremities (Jue Ni) would appear, which would correctly belong to the Sini Tang syndrome of Shaoyin disease. From this perspective, the superficiality of exterior pathogens makes the counterintuitive fever relatively mild; the decline of healthy qi makes the counterintuitive deep pulse relatively severe. Thus, the importance of Sini Tang is not inferior to that of Mahuang Fuzi Xixin Tang. Furthermore, it can be seen that Prepared Aconite paired with Ephedrae Herba provides tonification within dispersion, while Raw Aconite paired with Dried Ginger provides dispersion within tonification. The intent of Zhang Zhongjing is subtle and profound.
Ephedrae Herba (Mahuang, 麻黄), Aconiti Lateralis Radix Praeparata (Fuzi, 附子), Glycyrrhizae Radix et Rhizoma (Gancao, 甘草)
Shaoyin disease. After two or three days, use this decoction to induce slight sweating. Because there are no distinct exterior symptoms, only slight sweating is induced.
Commentary: The pulses in Shaoyin symptoms are mostly deep. If the pulse is deep and tight (Jin), sweating is contraindicated; if the pulse is deep, fine, and rapid (Shu), the disease is in the interior, and sweating is contraindicated. This symptom must present with a deep pulse and wheezing (Chuan), indicating cold in the exterior but no pathogen in the interior. Therefore, slightly pungent medicines are used to induce slight sweating. Commentary: The sweating decoctions of Zhang Zhongjing are categorized by weight and lightness, such as Mahuang Tang, Guizhi Tang, Da Qing Long Tang, and Yue Bi Tang, each having distinctions. Regarding the two sweating decoctions for Shaoyin disease, although both use Ephedrae Herba and Aconiti Lateralis Radix Praeparata, there are differences in weight and lightness. Thus, adding Asari Radix et Rhizoma makes it heavier, while adding Glycyrrhizae Radix et Rhizoma makes it lighter, based on the principle that pungent substances disperse and sweet substances moderate. For the first symptom, because Shaoyin inherently lacks heat, but now there is fever, it is termed "counterintuitive." Fever is due to exterior pathogens and requires sweating; additionally, the deep pulse belongs to Yin and requires warming. Therefore, Aconiti Lateralis Radix Praeparata warms the meridians, Ephedrae Herba releases the exterior, and the heat resolves through sweating. Hence, adding Asari Radix et Rhizoma results in a heavier sweating formula. For the second symptom, since there is no interior cold to warm and no interior heat to purge, the rationale for using Ephedrae Herba and Aconiti Lateralis Radix Praeparata is that a deep pulse allows the name Shaoyin disease, and body fever permits the administration of sweating medicines. Having had the disease for two or three days, the pathology is still shallow and slightly milder than the previous symptom. Therefore, the pulse and symptoms are not emphasized again, only stating "slight sweating." Thus, removing Asari Radix et Rhizoma and adding Glycyrrhizae Radix et Rhizoma results in a lighter sweating formula.