甘草（炙） 枳实（破，水渍，炙干） 柴胡 芍药
右四味，各十分，捣筛，白饮和服方寸匕，日三服。
咳者，加五味子、干姜各五分，并主下利。悸者，加桂枝五分。小便不利者，加茯苓
五分。腹中痛者，加附子一枚，炮令折。
泻利下重者，先以水五升，煮薤白三升，煮取三升，去滓，以散三方寸匕，纳汤中，
煮取一升半，分温再服。
【方解】
方名四逆散，与四逆汤均治手足逆冷，但四逆汤治阴邪寒厥，此则治阳邪热厥。热厥
者，三阳传厥阴合病也。太阳厥阴，麻黄升麻汤、甘草干姜汤证也；阳明厥阴，白虎
汤、大承气汤证也。此则少阳厥阴，故君柴胡以疏肝之阳，臣芍药以泻肝之阴，佐甘
草以缓肝之气，使枳实以破肝之逆，三物得柴胡，能外走少阳之阳，内走厥阴之阴，
则肝胆疏泄之性遂，而厥可通也。或咳或下利者，邪饮上下为病，加五味子、干姜，
温中以散饮也。或悸者，饮停侮心，加桂枝通阳以益心也。或小便不利者，饮蓄膀胱
，加茯苓利水以导饮也。或腹中痛者，寒凝于里，加附子温中以定痛也。或泻利下重
者，寒热郁结，加薤白开结以疏寒热也。
【集解】
方有执曰：人之四肢，温和为顺，故以不温和为逆，但不温和而未至于厥冷，则热犹
未深入也，故用柴胡以解之，枳实以泻之，芍药以收之，甘草以和之也。
@@@
少阴病，下利，若利自止，恶寒而蜷卧，手足温者，可治。
【注】
少阴病，恶寒厥冷下利不止者，阴寒盛也。今下利能自止，手足能自温，虽见恶寒蜷
卧，乃阴退阳回之兆，故曰可治。
【集注】
程应旄曰：少阴病，下利而利自止，则阴寒亦得下袪，而又不致于脱，虽有恶寒蜷卧
不善之证，但使手足温者，阳气有挽回之机，故可温而救之也。
沈明宗曰：手足温者，乃真阳未离，急用白通四逆之类，温经散寒，则邪退而真阳复
矣，故曰可治。
@@@
少阴病，恶寒而蜷，时自烦，欲去衣被者，可治。
【注】
少阴病，恶寒而蜷，阴寒证也。若时自烦欲去衣被者，此阳回阴退之征，故曰可治。
@@@
少阴病，得之二、三日以上，心中烦，不得卧，黄连阿胶汤主之。
【注】
此承上条以出其治也。少阴病，得之二、三日以上，谓或四、五日也。言以二、三日
少阴之但欲寐，至四、五日反变为心中烦不得卧，且无下利清谷咳而呕之证，知非寒
也，是以不用白通汤；非饮也，亦不用猪苓汤；乃热也，故主以黄连阿胶汤，使少阴
不受燔灼，自可愈也。
【集注】
程知曰：二、三日邪在少阴，四、五日已转属阳明，故无呕利厥逆诸证。而心烦不得
卧者，是阳明之热，内扰少阴，故不欲寐也，当以解热滋阴为主治也。
【方解】
方剂名称为四逆散，它与四逆汤都用于治疗手足逆冷（手脚冰凉），但四逆汤治疗的是阴寒邪气导致的寒厥，而本方治疗的是阳热邪气导致的热厥。所谓热厥，是三阳经病邪传入厥阴经的合病证候。太阳经与厥阴经同病，适用麻黄升麻汤或甘草干姜汤；阳明经与厥阴经同病，适用白虎汤或大承气汤。本方针对的是少阳经与厥阴经同病，因此以柴胡为君药来疏泄肝气的阳气，以芍药为臣药来清泻肝血的阴分，以甘草为佐药来缓和肝气的急迫，以枳实为使药来破滞降逆。前三味药配合柴胡，能够向外通达少阳之阳，向内通达厥阴之阴，从而使肝胆的疏泄功能恢复正常，手足厥逆得以通畅。如果伴有咳嗽或腹泻，是邪气与水饮上下为患，加入五味子和干姜各五分，以温中散饮。如果伴有心悸，是水饮停聚克制心火，加入桂枝五分，以通阳益心。如果伴有小便不利，是水饮蓄积在膀胱，加入茯苓五分，以利水导饮。如果伴有腹中疼痛，是寒气凝滞于体内，加入一枚炮制的附子，以温中定痛。如果伴有腹泻且肛门重坠感，先用五升水煮三升薤白，煮取三升药液，去渣，将四逆散三方寸匕的药粉纳入汤中，再煮取一升半药液，分两次温服。
【集解】
方有执说：人的四肢，温暖柔和为顺，所以不温暖称为“逆”。但如果只是不温暖而没有达到厥冷的程度，说明热邪尚未深入，所以用柴胡来解表，枳实来泻实，芍药来收敛，甘草来调和。
@@@
少阴病，出现下利，如果腹泻自行停止，虽有恶寒和蜷缩卧倒的表现，但手足温暖，这是可以治疗的。
【注】
少阴病，如果出现恶寒、厥冷且下利不止，属于阴寒盛极。现在下利能自行停止，手足能自行变暖，虽然见到恶寒蜷卧的症状，但这却是阴邪退去、阳气回复的征兆，所以说可以治疗。
【集注】
程应旄说：少阴病，下利而腹泻自行停止，那么阴寒之邪也能向下祛除，而且不至于发生脱证，虽然有恶寒蜷卧等不好的症状，但只要手足温暖，就说明阳气有挽回的生机，所以可以用温法来救治。
沈明宗说：手足温暖，说明真阳没有离散，应当紧急使用白通汤或四逆汤之类的方剂，温经散寒，这样邪气退去而真阳就能恢复，所以说可以治疗。
@@@
少阴病，出现恶寒且身体蜷缩，偶尔自觉心烦，想要去掉衣被的，是可以治疗的。
【注】
少阴病，恶寒且身体蜷缩，属于阴寒证。如果偶尔自觉心烦，想要去掉衣被，这是阳气回复、阴邪退去的征象，所以说可以治疗。
@@@
少阴病，患病两三天以上，心中烦乱，无法入睡的，主治方为黄连阿胶汤。
【注】
此条承接上一条以阐述治疗方法。少阴病，患病两三天以上，指的是可能到了四五天。意思是说，从二三天时少阴病的只想睡觉（但欲寐），到了四五天反而变成心中烦乱、无法入睡，并且没有下利完谷不化、咳嗽呕吐等症状，知道这不是寒证，所以不用白通汤；不是水饮证，也不用猪苓汤；而是热证，所以主治以黄连阿胶汤，使少阴心肾不受火热燔灼，自然可以痊愈。
【集注】
程知说：二三天时邪气在少阴，四五天时已经转属阳明，所以没有呕吐、下利、厥逆等各种症状。而心烦不得卧，是阳明的热邪内扰少阴，所以不想睡觉，治疗当以清热滋阴为主。
[Formula Analysis]
The formula is named Sini San (Four Reversals Powder). Like Sini Tang (Cinnamon Twig, Aconite, and Licorice Decoction), it treats cold extremities (cold hands and feet); however, Sini Tang treats cold reversal caused by Yin-cold pathogenic factors, whereas this formula treats heat reversal caused by Yang-heat pathogenic factors. Heat reversal refers to a combined syndrome where pathogenic factors from the Three Yang meridians transmit to the Jueyin meridian. When the Taiyang and Jueyin meridians are involved simultaneously, Mahuang Shengma Tang (Ephedra and Asiasarum Decoction) or Gancao Ganjiang Tang (Licorice and Dried Ginger Decoction) are indicated; when the Yangming and Jueyin meridians are involved simultaneously, Baihu Tang (White Tiger Decoction) or Dachengqi Tang (Major Order the Qi Decoction) are indicated. This formula addresses the simultaneous involvement of the Shaoyang and Jueyin meridians. Therefore, Chaihu (Bupleuri Radix) is used as the Sovereign herb to soothe the Yang of the Liver; Shaoyao (Paeoniae Radix Alba) is used as the Minister herb to drain the Yin of the Liver; Gancao (Glycyrrhizae Radix et Rhizoma Preparata) is used as the Assistant herb to moderate the Qi of the Liver; and Zhishi (Aurantii Fructus Immaturus) is used as the Envoy herb to break stagnation and direct rebellious Qi downward. With the aid of Chaihu, these three herbs can reach outward to the Yang of the Shaoyang and inward to the Yin of the Jueyin, thereby restoring the dispersing and descending functions of the Liver and Gallbladder, allowing the reversal of cold to be resolved. If cough or diarrhea occurs, it indicates pathogenic factors and fluid retention affecting the upper and lower body; add Wuweizi (Schisandrae Chinensis Fructus) and Ganjiang (Zingiberis Rhizoma) each in 5 fen to warm the middle and dissipate fluid retention. If palpitations occur, it indicates fluid retention suppressing the Heart; add Guizhi (Cinnamomi Ramulus) in 5 fen to unblock Yang and benefit the Heart. If urination is difficult, it indicates fluid accumulation in the Bladder; add Fuling (Poria) in 5 fen to promote urination and guide out fluid retention. If abdominal pain occurs, it indicates cold coagulation in the interior; add one Pao Fu Zi (Aconiti Lateralis Radix Praeparata), roasted until broken, to warm the middle and relieve pain. If diarrhea with a sensation of heaviness in the rectum occurs, first boil Xiebai (Allii Macrostemonis Bulbus) in five sheng of water using three sheng of the herb, reduce to three sheng, strain, then add three fangcunbi (square-inch spoonfuls) of the powder into the decoction, boil until reduced to one and a half sheng, and divide into two doses to be taken warm.
[Collected Explanations]
Fang Youzhi stated: The limbs of humans should be warm and gentle, which is considered favorable ("Shun"); thus, lack of warmth is termed "Ni" (Reversal). However, if there is merely a lack of warmth without reaching the state of cold reversal, it indicates that the heat pathogen has not yet penetrated deeply. Therefore, Chaihu is used to resolve the exterior, Zhishi to drain excess, Shaoyao to astringe, and Gancao to harmonize.
@@@
In Shaoyin disease, if there is diarrhea but the diarrhea stops spontaneously, and although there is aversion to cold and curling up in bed, the hands and feet are warm, the condition is treatable.
[Annotation]
In Shaoyin disease, aversion to cold, cold reversal, and incessant diarrhea indicate an excess of Yin-cold. Now, since the diarrhea stops spontaneously and the hands and feet become warm on their own, even though symptoms of aversion to cold and curling up are present, this is a sign that Yin pathogens are receding and Yang energy is returning. Hence, it is said to be treatable.
[Collected Annotations]
Cheng Yingmao stated: In Shaoyin disease, if diarrhea stops spontaneously, the Yin-cold pathogen can be expelled downward without leading to collapse. Although there are unfavorable signs like aversion to cold and curling up, as long as the hands and feet are warm, it indicates that Yang Qi has the potential to recover; therefore, warming methods can be used to rescue it.
Shen Mingzong stated: Warm hands and feet indicate that the True Yang has not dispersed. One should urgently use formulas such as Baitong Tang (Alisma, Aconite, and Licorice Decoction) or Sini Tang to warm the meridians and dispel cold. Once the pathogen retreats, True Yang will recover; hence, it is said to be treatable.
@@@
In Shaoyin disease, if there is aversion to cold and curling up, occasional spontaneous irritability, and a desire to remove clothing and bedding, the condition is treatable.
[Annotation]
Shaoyin disease characterized by aversion to cold and curling up is a Yin-cold syndrome. If there is occasional spontaneous irritability and a desire to remove coverings, this is a sign of Yang recovery and Yin recession; hence, it is said to be treatable.
@@@
In Shaoyin disease, after two or more days, if there is mental restlessness in the heart and inability to sleep, Huanglian Ejiao Tang (Coptis and Donkey-Hide Gelatin Decoction) is the primary treatment.
[Annotation]
This clause follows the previous one to explain the treatment. Shaoyin disease occurring after two or more days implies it may have reached four or five days. It means that while the patient initially presented with excessive sleepiness ("Dan Yu Mei") typical of early Shaoyin disease, by the fourth or fifth day, this changes to mental restlessness and insomnia. Furthermore, the absence of symptoms like diarrhea with undigested food, cough, or vomiting indicates this is not a cold syndrome, so Baitong Tang is not used; nor is it a fluid-retention syndrome, so Zhuling Tang is not used. It is a heat syndrome, so Huanglian Ejiao Tang is prescribed to prevent the Shaoyin system from being scorched by heat, leading to natural recovery.
[Collected Annotations]
Cheng Zhi stated: At two or three days, the pathogen is in the Shaoyin; by four or five days, it has transferred to the Yangming. Thus, there are no symptoms of vomiting, diarrhea, or cold reversal. The mental restlessness and inability to sleep result from Yangming heat disturbing the Shaoyin internally, causing insomnia. Treatment should primarily focus on clearing heat and nourishing Yin.