《甲乙经》云∶经者所不可见者也，络者所可见者也，外之沟渠是已。然络亦有不可见
者乎
，何以知之？黄帝曰∶邪热入于阳络，则为鼻血；邪热入于阴络，则为后血。以是知阴络病
也。鼻血者在上，溺与后血者在下也，若吐呕者，是知在中也。至于伤寒上厥下竭之证，或
从耳目，或从口鼻，血俱出于上窍，然各随其脏与经也。
扁鹊云∶病若谵言妄语，身常有热，脉当洪大而反手足厥逆，脉沉细而微者死也。
又云∶假令心病，何以知伤寒得之？然当谵言妄语。何以言之？肺主声，故知肺邪入心，
为谵言妄语也。其病身热，洒洒恶寒，甚则唾咳。其脉浮大而涩。
仲景云∶谵言妄语，身微热，脉浮大，手足温者生，逆冷脉沉细者，不过一日死矣！
又云∶谵言妄语，脉涩者死。
以上皆阳证得阴脉也。
又云∶发汗多，重发汗者必亡其阳，谵语脉短者死。
上此重发汗亡阳者，变阴也，又得阴脉死也。
成无己云∶伤风自汗，汗出恶风寒者，有表也。汗出不恶风寒者，表解里未和也。有阳
明发热汗出，此为热越。有阳明发热汗多者，下之。
海藏云∶内感伤冷，自汗，大恶风寒，汗出身凉不热者，阴证也；汗出身热得阴脉者，
亦阴证也。
手少阳之脉，三焦之经，起于小指次指之端，上出两指之间，循手表腕，出臂外两骨之
间，上贯肘云云。手背遍多者，三焦之气脱也。经云∶手足 然汗出，大便硬而谵语，下之则愈
。以其热聚胃，津液旁达，故手足 汗出也。成无己云∶寒聚于胃，有手足汗出者乎？经
云∶阳明中寒者不能食，小便不利，手足 然汗出，欲作痼瘕，即是中寒也。
海藏云∶故内感阴证，有手足逆冷而自汗者，手足自温而自汗者，厥阴、太阴之异也。
上此一条，虽是三焦四逆温和，关他二经，不可不知。
《甲乙经》说：经脉是深藏体内不可见的，络脉是浮于体表可见的，就像体外的沟渠一样。然而络脉也有不可见的吗？怎么知道呢？黄帝说：邪热侵入阳络，就会流鼻血；邪热侵入阴络，就会便血。由此可知这是阴络的病变。鼻出血的部位在上部，尿血和便血的部位在下部，如果是吐血、呕吐，则病位在中部。至于伤寒病中上厥下竭的证候，有的从耳目出血，有的从口鼻出血，血液都从上窍流出，但具体取决于病变所在的脏腑与经络。
扁鹊说：如果病人胡言乱语、神志不清，身体常有发热，脉象应当洪大，反而出现手足厥冷，脉象沉细而微弱，这是死证。
又说：假使是心病，如何判断是由伤寒引起的？应当表现为胡言乱语、神志不清。为什么这样说呢？肺主声音，所以知道是肺邪传入心脏，导致胡言乱语、神志不清。这种病症身体发热，怕冷如冷水洒身，严重时咳嗽唾痰。脉象浮大而涩。
张仲景说：胡言乱语、神志不清，身体微热，脉象浮大，手足温暖的可以生还；如果手足逆冷，脉象沉细的，不超过一天就会死亡！
又说：胡言乱语、神志不清，脉象涩滞的，是死证。
又说：发汗过多，再次发汗的人必然亡失阳气，出现谵语且脉短促的，是死证。
上述因重发汗导致亡阳的，是转化为阴证，又出现阴脉，所以死亡。
成无己说：伤风导致的自汗，出汗且怕风怕冷的，说明表证仍在。出汗但不怕风不怕冷的，说明表证已解，但里气未调和。有阳明病发热出汗的，这是热邪向外发散。有阳明病发热且汗多的，应当用攻下法治疗。
李东垣（海藏）说：内感寒邪导致的自汗，极度怕风怕冷，出汗后身体凉爽不热的，属于阴证；出汗后身体发热却出现阴脉的，也属于阴证。
手少阳三焦经的经脉，起于无名指末端，向上出于两指之间，沿手背手腕，出于前臂外侧两骨之间，向上穿过肘部等等。如果手背部多处异常，是三焦之气脱失的表现。经文说：手足濈然汗出，大便干硬且胡言乱语，用攻下法就可以痊愈。因为热邪聚集在胃，津液旁达四肢，所以手足濈然汗出。成无己说：寒邪聚集在胃，会有手足汗出的情况吗？经文说：阳明中寒的病人不能进食，小便不利，手足濈然汗出，想要形成积块，这就是中寒证。
The *Jia Yi Jing* (Classical Text of Jia Yi) states: Meridians are deep and invisible, while collaterals are superficial and visible, akin to ditches on the exterior. However, are there also invisible collaterals? How do we know? The Yellow Emperor said: When pathogenic heat enters the Yang Collaterals, epistaxis occurs; when it enters the Yin Collaterals, hematochezia or hematuria occurs. From this, we know it is a disease of the Yin Collaterals. Epistaxis occurs in the upper part, while hematuria and hematochezia occur in the lower part. If vomiting blood or regurgitation occurs, the pathology is located in the middle. As for the syndrome of upper cold and lower exhaustion in Shanghan (Cold Damage), bleeding may occur from the ears and eyes or from the mouth and nose, with all blood emerging from the upper orifices, yet each case follows its respective Zang organ and meridian.
Bian Que said: If a patient speaks deliriously and incoherently, with constant body heat, the pulse should be large and flooding. If instead there is coldness of the hands and feet, and the pulse is deep, fine, and faint, death ensues.
He further stated: Suppose it is a Heart disease; how can one determine it arises from Shanghan? It should present as delirious speech. Why? The Lung governs sound; thus, knowing that Lung pathogen has entered the Heart causes delirious speech. The symptoms include body heat, aversion to wind and cold as if sprinkled with water, and in severe cases, coughing with sputum. The pulse is floating, large, and choppy.
Zhang Zhongjing said: Delirious speech, slight body heat, floating and large pulse, and warm hands and feet indicate survival. Cold hands and feet with a deep and fine pulse indicate death within one day!
He also said: Delirious speech with a choppy pulse indicates death.
All the above describe Yang syndromes presenting with Yin pulses.
He further said: Excessive sweating, or sweating again after prior sweating, will inevitably lead to the loss of Yang Qi. Delirium with a short pulse indicates death.
The aforementioned case of Yang loss due to excessive sweating transforms into a Yin syndrome; combined with the appearance of a Yin pulse, death results.
Cheng Wuji said: In Wind Injury with spontaneous sweating, sweating accompanied by aversion to wind and cold indicates the presence of an Exterior syndrome. Sweating without aversion to wind and cold indicates the Exterior syndrome has resolved, but the Interior is not yet harmonized. In Yangming syndrome with fever and sweating, this represents the dissipation of heat. In Yangming syndrome with fever and profuse sweating, purgation should be used.
Li Dongyuan (Haizang) said: Spontaneous sweating caused by internal contraction of cold, with extreme aversion to wind and cold, and a cool body temperature after sweating, constitutes a Yin Syndrome. Spontaneous sweating with body heat but a Yin pulse also constitutes a Yin Syndrome.
The Hand Shaoyang Sanjiao Meridian originates at the tip of the fourth finger, ascends between the fingers, follows the dorsal wrist, emerges between the two bones of the forearm, and ascends through the elbow, etc. Abundant manifestations on the back of the hand indicate the depletion of Sanjiao Qi. The Classic states: Profuse sweating of the hands and feet, hard stool, and delirium are cured by purgation. Because heat gathers in the Stomach, fluids reach the extremities peripherally, causing profuse sweating of the hands and feet. Cheng Wuji asked: Can cold gathering in the Stomach cause sweating of the hands and feet? The Classic states: Patients with Middle Cold in the Yangming channel cannot eat, have difficult urination, and exhibit profuse sweating of the hands and feet, indicating an impending accumulation mass; this is indeed Middle Cold.
Li Dongyuan (Haizang) said: Therefore, in internally contracted Yin Syndromes, there are cases of spontaneous sweating with cold limbs, and cases of spontaneous sweating with warm limbs; these distinguish the Jueyin and Taiyin channels.
Although the above passage discusses the Sanjiao and variations in limb temperature (cold vs. warm), it relates to other meridians and must not be ignored.