少阴为太阳之里。居厥太二阴之间。故有邪在太阳。而已内及少阴者。有寒中少阴。而仍外连
太阳者。有邪在少阴。而或兼厥阴。或兼太阴者。大抵连太阴者多发热。连厥阴者多厥利也。是传
经直中之外。又有不同如此。且也直中之寒。久亦化热。传经之热。极必生阴。兹篇先列脉证于前
。次清法。次温法。又次为生死法。欲学人明辨宜清宜温之实。不必但泥传经直中之名也。又其次
为少阴病禁。以少阴为汗下之例。亦不得不着汗下之禁云。凡四十五条。为一卷。
少阴之为病。脉微细。但欲寐也。
经脉阳浅而阴深。阳大而阴小。邪传少阴。则脉之浮者转为微。大者转为细也。又多阳者多
寤。多阴者多寐。邪传少阴则目不瞑者。转而为但欲寐也。夫少阴者。三阴之枢也。阳于是乎入。
而阴于是乎出。故
虽太阴厥阴同为阴脏。而其为病。实惟少阴为然。而少阴之为病。亦非独脉微细但欲寐二端。仲景
特举此者。以为从阳入阴之际。其脉证变见有如此。
少阴病。欲吐不吐。心烦。但欲寐。五六日。自利而渴者。属少阴也。虚故引水自救。若小
便色白者。少阴病形悉具。小便白者。以下焦虚有寒。不能制水故令色白也。
此少阴自受寒邪之证。不从阳经来也。寒初到经。欲受不可。欲却不能。故欲吐不吐。心烦。但
欲寐。而实不能寐也。至五六日。自利而渴。则其邪已入少阴之脏矣。然少阴阴脏也。寒阴邪也。
以阴受阴。法当不渴。而渴者。此非有热。以脏虚故引水自救耳。更审其小便。若色白者。则少阴
寒病。全体大露无疑。何以言之。热传少阴。自利而渴者。邪热足以消水。其小便色必赤。寒中少
阴。自利而渴者。虽能饮而不能制。其小便色必白也。仲景辨证之精如此。
病患脉阴阳俱紧。反汗出者。亡阳也。此属少阴。法当咽痛而复吐利。
阴阳俱紧。太阳伤寒之脉也。法当无汗。而反汗出者。表虚亡阳。其病不属太阳而属少阴矣。
少阴之脉。上膈循喉咙。少阴之脏。为胃之关。为二阴之司。寒邪直入。经脏俱受。故当咽痛而复
吐利也。此为寒伤太阳。阳虚不任。因遂转入少阴之证。盖太阳者。少阴之表。犹唇齿也。唇亡则齿
寒。阳亡则阴及。故曰少阴之邪从太阳飞渡者多也。
少阴病。八九日。一身手足尽热者。以热在膀胱。必便血也。
此热传少阴。而复还入膀胱之证。膀胱者。太阳也。太阳为三阳之表。而多血少气。热在膀胱。
则一身手足尽热。而热气有余。血为热迫。散而下行。则必便血也。
少阴经是太阳经的里层。它位于厥阴和太阴这两条阴经之间。因此，有的情况是邪气在太阳经，但已经内传影响到少阴；有的是寒邪直接中伤少阴，但仍然外连太阳经；有的是邪气在少阴经，或者兼夹厥阴经病证，或者兼夹太阴经病证。大抵来说，兼夹太阴经的多表现为发热，兼夹厥阴经的多表现为四肢厥冷和下利。除了传经和直中这两种情况之外，还有如此不同的变化。况且，直中的寒邪，时间久了也会化热；传经的热邪，极盛时必然损伤阴液。这一篇先列出脉象和症状在前面，接着讲清法（清热之法），再讲温法（温补之法），又接着讲判断生死的方法。目的是让学习者明白应当使用清法还是温法的实际情况，不必仅仅拘泥于“传经”或“直中”的名称。最后部分是少阴病的禁忌，因为少阴病涉及发汗和攻下的法则，也不得不注明发汗和攻下的禁忌。总共四十五条，构成一卷。
少阴病的典型表现是：脉象微细，精神萎靡只想睡觉。
经脉方面，阳经浅而阴经深，阳脉大而阴脉小。邪气传入少阴，则脉象由浮转为微，由大转为细。另外，多阳气的人多清醒，多阴气的人多嗜睡。邪气传入少阴，原本目不瞑（睡不着）的情况，转变为只想睡觉。少阴经是三阴经的枢纽，阳气由此入里，阴气由此出表。所以虽然太阴和厥阴同为阴脏，但它们发病时的表现，实际上只有少阴病是这样。而少阴病的表现，也不仅仅是脉微细、只想睡觉这两点。张仲景特别列举这两点，是为了说明从阳经转入阴经之际，其脉象和症状的变化有如此特点。
少阴病，想吐却吐不出来，心烦，只想睡觉。过了五六天，出现自发性下利且口渴的，属于少阴病。这是因为内脏虚寒，所以饮水来自救。如果小便颜色发白的，少阴病的形貌就完全具备了。小便发白，是因为下焦虚寒，不能制约水液，所以导致颜色发白。
这是少阴经直接感受寒邪的证候，不是从阳经传来的。寒邪刚到达经络，想要承受它不行，想要排斥它也不能，所以想吐却吐不出来，心烦，只想睡觉，但实际上并不能真正睡着。到了五六天，出现自发性下利且口渴，那么邪气已经进入少阴之脏了。然而少阴是阴脏，寒邪也是阴邪，以阴受阴，按理说不应该口渴。之所以口渴，这不是因为有热，而是因为脏气虚寒，所以引水来自救。进一步审查其小便，如果颜色发白，那么少阴寒病的真相就完全暴露无疑了。为什么这样说呢？如果是热邪传入少阴，自发性下利且口渴的，邪热足以消耗水液，其小便颜色必定发红。如果是寒邪直中少阴，自发性下利且口渴的，虽然能喝水但不能气化制约，其小便颜色必定发白。张仲景辨证的精妙之处就在于此。
患者脉象寸关尺三部都紧，反而出汗的，是亡阳。这属于少阴病，按理应当咽喉疼痛并且伴有呕吐和下利。
寸关尺三部脉都紧，是太阳伤寒的脉象。按理应当无汗，反而出汗的，是表虚亡阳。其病不属太阳而属少阴了。
少阴经脉，上行穿过膈肌，沿着喉咙。少阴之脏，是胃的关口，主管前后二阴。寒邪直入，经络和脏腑同时受邪，所以应当出现咽喉疼痛并且伴有呕吐和下利。这是寒邪伤害太阳，阳气虚弱不能胜任，因而转入少阴的证候。大概太阳是少阴的表，就像嘴唇和牙齿的关系。嘴唇没了牙齿就会受寒，阳气亡失阴气就会受累。所以说少阴的邪气从太阳飞渡过来的很多。
少阴病，经过八九天，全身和手足都发热的，是因为热在膀胱，一定会出现便血。
这是热邪传入少阴，然后又返还进入膀胱的证候。膀胱就是太阳经。太阳经是三阳经的表层，而且多血少气。热在膀胱，则全身和手足都发热，而且热气有余，血液被热邪逼迫，散乱而下走，那么就一定会出现便血。
Shaoyin is the interior of Taiyang. It resides between Jueyin and Taiyin. Therefore, there are cases where pathogenic factors are in Taiyang but have already affected Shaoyin internally; cases where cold directly strikes Shaoyin but still connects externally to Taiyang; and cases where pathogenic factors are in Shaoyin, either complicating with Jueyin or complicating with Taiyin. Generally, those complicating with Taiyin often present with fever, while those complicating with Jueyin often present with cold limbs and diarrhea. Besides transmission through meridians (Chuanjing) and direct strike (Zhizhong), there are such differences. Moreover, cold from direct strike may transform into heat over time, and heat from transmission may generate Yin deficiency when extreme. This chapter first lists pulse and symptoms, then discusses clearing methods (Qingfa), followed by warming methods (Wenfa), and subsequently methods for determining life and death. The aim is to enable learners to clearly distinguish the practical application of clearing versus warming, rather than merely adhering to the names of "transmission" or "direct strike." Finally, it covers contraindications for Shaoyin disease. Since Shaoyin disease involves principles of sweating and purging, contraindications for these methods must also be noted. There are forty-five clauses in total, forming one volume.
The manifestation of Shaoyin disease is a faint and fine pulse, and a desire only to sleep.
Regarding meridians, Yang channels are superficial and Yin channels are deep; Yang pulses are large and Yin pulses are small. When pathogens transmit to Shaoyin, floating pulses become faint, and large pulses become fine. Furthermore, those with abundant Yang are often awake, while those with abundant Yin are often sleepy. When pathogens transmit to Shaoyin, the state of being unable to close the eyes transforms into a desire only to sleep. Shaoyin is the pivot of the three Yin channels; Yang enters here, and Yin exits here. Thus, although Taiyin and Jueyin are both Yin organs, their pathological manifestations are uniquely characteristic of Shaoyin. Moreover, Shaoyin disease is not limited to just faint/fine pulses and somnolence. Zhang Zhongjing specifically highlights these two aspects to illustrate that at the juncture of transitioning from Yang to Yin, pulse and symptom changes manifest in this manner.
In Shaoyin disease, if the patient desires to vomit but cannot, feels irritability, and desires only to sleep; after five or six days, if spontaneous diarrhea occurs accompanied by thirst, it belongs to Shaoyin. This is due to internal deficiency causing the patient to draw water to self-rescue. If the urine is white, the signs of Shaoyin disease are fully present. White urine indicates deficiency-cold in the Lower Jiao, which fails to control water metabolism, resulting in white coloration.
This represents Shaoyin contracting cold pathogens directly, not transmitted from Yang channels. When cold initially reaches the channel, the body struggles to accept or reject it, leading to the desire to vomit without success, irritability, and a desire to sleep (though actual sleep is difficult). By the fifth or sixth day, spontaneous diarrhea and thirst indicate the pathogen has entered the Shaoyin Zang organ. However, Shaoyin is a Yin Zang, and cold is a Yin pathogen; receiving Yin with Yin should theoretically not cause thirst. The presence of thirst here is not due to heat, but because the Zang is deficient and cold, prompting the patient to seek water for self-rescue. Further examination of the urine: if white, the nature of Shaoyin cold disease is unmistakably revealed. Why? In cases where heat transmits to Shaoyin with spontaneous diarrhea and thirst, the pathogenic heat consumes fluids, making the urine red. In cases where cold directly strikes Shaoyin with spontaneous diarrhea and thirst, although the patient can drink, they cannot metabolize/transform it, making the urine white. Such is the precision of Zhang Zhongjing’s differentiation.
If a patient’s pulse is tight in all positions (Yin and Yang), yet sweat appears spontaneously, this indicates loss of Yang. This belongs to Shaoyin disease, and according to the law, should present with sore throat accompanied by vomiting and diarrhea.
A tight pulse in all positions is typical of Taiyang Cold Damage, which should present without sweat. Spontaneous sweating indicates exterior deficiency and loss of Yang. The disease thus shifts from Taiyang to Shaoyin.
The Shaoyin meridian ascends through the diaphragm and follows the throat. The Shaoyin Zang serves as the gate of the Stomach and governs the two lower orifices. Direct invasion by cold pathogens affects both the meridian and the Zang, hence the occurrence of sore throat, vomiting, and diarrhea. This is a case where cold damages Taiyang, Yang Qi becomes too weak to resist, and the condition transitions into Shaoyin. Taiyang is the exterior of Shaoyin, akin to lips and teeth; if the lips are gone, the teeth suffer cold; if Yang is lost, Yin is implicated. Hence, it is said that many Shaoyin pathogens transfer from Taiyang.
In Shaoyin disease, after eight or nine days, if the entire body and hands and feet become hot, it is because heat resides in the Bladder, and hematochezia (blood in stool) will inevitably occur.
This represents heat transmitting to Shaoyin and then returning to enter the Bladder. The Bladder corresponds to Taiyang. Taiyang is the exterior of the three Yang channels and is characterized by abundant blood and scarce Qi. Heat residing in the Bladder causes heat throughout the body and extremities. Excessive heat forces blood to scatter and flow downward, inevitably resulting in hematochezia.