寒热者，阴阳之化也。阴不足则阳乘之，其变为热；阳不足则阴乘之，其变为寒。故阴
胜则阳病，阴胜为寒也。阳胜则阴病，阳胜为热也。热极则生寒，因热之甚也；寒极则生热
，因寒之甚也。阳虚则外寒，寒必伤阳也；阴虚则内热，热必伤阴也。阳盛则外热，阳归阳
分也；阴盛则内寒，阴归阴分也。寒则伤形，形言表也；热则伤气，气言里也。故火旺之时
，阳有余而热病生；水旺之令，阳不足而寒病起。人事之病由于内，气交之病由于外。寒热
之表里当知，寒热之虚实亦不可不辨。
一、热在表者，为发热头痛，为丹肿斑黄，为揭去衣被，为诸痛疮疡。
一、热在里者，为瞀闷胀满，为烦渴喘结，或气急叫吼，或躁扰狂越。
一、热在上者，为头痛目赤，为喉疮牙痛，为诸逆冲上，为喜冷舌黑。
一、热在下者，为腰足肿痛，为二便秘涩，或热痛遗精，或溲混便赤。
一、寒在表者，为憎寒，为身冷，为浮肿，为容颜青惨，为四肢寒厥。
一、寒在里者，为冷咽肠鸣，为恶心呕吐，为心腹疼痛，为恶寒喜热。
一、寒在上者，为吞酸，为膈噎，为饮食不化，为嗳腐胀哕。
一、寒在下者，为清浊不分，为 溏痛泄，为阳痿，为遗尿，为膝寒足冷。
一、病患身大热，反欲得近衣者，热在皮肤，寒在骨髓也；身大寒，反不欲近衣者，寒
在皮肤，热在骨髓也，此表证之辨。若内热之甚者，亦每多畏寒，此当以脉证参合察之。
一、真寒之脉，必迟弱无神；真热之脉，必滑实有力。
一、阳脏之人多热，阴脏之人多寒。阳脏者，必平生喜冷畏热，即朝夕食冷，一无所病
，此其阳之有余也。阴脏者，一犯寒凉，则脾肾必伤，此其阳之不足也。第阳强者少，十惟
二三；阳弱者多，十常五六。然恃强者多反病，畏弱者多安宁。若或见彼之强而忌我之弱，
则与侏儒观场，丑妇效颦者无异矣。
寒热现象，是阴阳变化的结果。阴气不足则阳气乘虚而入，表现为热证；阳气不足则阴气乘虚而入，表现为寒证。因此，阴气偏胜则损伤阳气，阴气偏胜即为寒证。阳气偏胜则损伤阴气，阳气偏胜即为热证。热势极盛时会产生寒象，这是因为热邪过于深重所致；寒势极盛时会产生热象，这是因为寒邪过于深重所致。阳虚则体表感到寒冷，因为寒邪必然损伤阳气；阴虚则体内产生虚热，因为热邪必然耗伤阴液。阳盛则体表发热，因为阳气归属于阳分（体表）；阴盛则体内寒冷，因为阴气归属于阴分（体内）。寒邪主要损伤形体，形体指代体表；热邪主要损伤元气，元气指代体内。所以在火气旺盛的时候，阳气有余而热病发生；在水气旺盛的季节，阳气不足而寒病兴起。人事失调导致的疾病源于内部，气候交变导致的疾病源于外部。对于寒热病症，必须辨别其表里属性，也必须辨别其虚实性质。
第一，热在体表者，表现为发热头痛，表现为丹毒肿痛、斑疹发黄，表现为掀开衣被，表现为各种疼痛疮疡。
第二，热在体内者，表现为神志昏蒙、胸闷胀满，表现为烦躁口渴、气喘便秘，或者气急叫喊吼叫，或者躁动不安、狂乱越轨。
第三，热在上部者，表现为头痛目赤，表现为咽喉生疮、牙齿疼痛，表现为各种气逆冲上，表现为喜冷饮、舌苔发黑。
第四，热在下部者，表现为腰部和足部肿痛，表现为大小便不通畅涩滞，或者热痛伴遗精，或者小便浑浊、大便色赤。
第五，寒在体表者，表现为憎恶寒冷，表现为身体冰冷，表现为浮肿，表现为面容青紫惨白，表现为四肢寒冷厥逆。
第六，寒在体内者，表现为咽喉冷、肠鸣，表现为恶心呕吐，表现为心腹疼痛，表现为怕冷喜热。
第七，寒在上部者，表现为吞酸水，表现为噎膈（吞咽困难），表现为饮食不消化，表现为嗳气腐臭、腹胀呃逆。
第八，寒在下部者，表现为清浊不分，表现为溏泄腹痛，表现为阳痿，表现为遗尿，表现为膝盖寒冷、双脚冰凉。
第九，病人身体大热，反而想要靠近穿衣取暖的，是热在皮肤（表象），寒在骨髓（本质）；身体大寒，反而不想靠近穿衣取暖的，是寒在皮肤（表象），热在骨髓（本质），这是辨别表证的要点。如果体内热邪极盛，也常常出现畏寒症状，这应当结合脉象和证候综合考察。
第十，真寒证的脉象，必定迟慢、微弱且无神气；真热证的脉象，必定滑利、实大且有力。
第十一，阳脏体质的人多患热病，阴脏体质的人多患寒病。所谓阳脏人，必定平生喜欢冷饮、畏惧热天，即使早晚吃冷的东西，也不会生病，这是其阳气有余的表现。所谓阴脏人，一旦接触寒凉之物，脾肾必然受损，这是其阳气不足的表现。然而阳气强盛的人很少，十人中只有两三人；阳气虚弱的人很多，十人中常有五六人。但是倚仗阳气强盛的人往往反而容易生病，畏惧阳气虚弱（即注意保养）的人往往更加安康。如果看见别人阳气强盛就忌妒自己阳气虚弱，那就与矮个子看戏、丑妇模仿西施捧心皱眉没有什么区别了。
Cold and heat are the transformations of Yin and Yang. When Yin is insufficient, Yang takes advantage of it, resulting in heat; when Yang is insufficient, Yin takes advantage of it, resulting in cold. Therefore, an excess of Yin damages Yang, and an excess of Yin constitutes a cold syndrome. An excess of Yang damages Yin, and an excess of Yang constitutes a heat syndrome. Extreme heat generates cold phenomena due to the severity of heat; extreme cold generates heat phenomena due to the severity of cold. Yang deficiency leads to external cold, as cold inevitably damages Yang; Yin deficiency leads to internal heat, as heat inevitably damages Yin. Yang excess leads to external heat, as Yang belongs to the Yang aspect (exterior); Yin excess leads to internal cold, as Yin belongs to the Yin aspect (interior). Cold damages the form (referring to the exterior), while heat damages Qi (referring to the interior). Thus, during periods of vigorous Fire, there is an excess of Yang and heat diseases arise; during seasons of vigorous Water, there is an insufficiency of Yang and cold diseases arise. Diseases caused by human activities stem from the interior, while diseases caused by climatic interactions stem from the exterior. One must understand the exterior-interior distinction of cold and heat, and one must not fail to differentiate their deficiency-excess nature.
First, heat located in the exterior manifests as fever and headache, as erysipelas swelling and yellowish rashes, as removing clothes and blankets, and as various painful sores and ulcers.
Second, heat located in the interior manifests as mental confusion, chest tightness, and abdominal fullness, as irritability, thirst, asthma, and constipation, or as rapid breathing with shouting, or as restlessness and mania.
Third, heat located in the upper part manifests as headache and red eyes, as throat sores and toothache, as various rebellious Qi rushing upward, as a preference for cold drinks and a black tongue coating.
Fourth, heat located in the lower part manifests as swelling and pain in the waist and feet, as difficult and scanty urination and defecation, or as painful seminal emission accompanied by heat, or as turbid urine and reddish stool.
Fifth, cold located in the exterior manifests as aversion to cold, as a cold body, as edema, as a blueish and miserable facial complexion, and as cold and cold-convulsion of the four limbs.
Sixth, cold located in the interior manifests as a cold throat and intestinal rumbling, as nausea and vomiting, as heart and abdominal pain, and as aversion to cold with a preference for warmth.
Seventh, cold located in the upper part manifests as acid regurgitation, as dysphagia (difficulty swallowing), as indigestion of food, as belching with a rotten smell, abdominal distension, and hiccups.
Eighth, cold located in the lower part manifests as the failure to distinguish between clear and turbid substances, as loose stools with abdominal pain, as impotence, as urinary enuresis, and as cold knees and cold feet.
Ninth, if a patient has a high fever but desires to cover up with clothes, the heat is at the skin level (superficial) while the cold is in the bone marrow (deep); if a patient feels very cold but does not desire to cover up, the cold is at the skin level (superficial) while the heat is in the bone marrow (deep). This is the differentiation of exterior syndromes. However, severe internal heat often presents with aversion to cold; this should be examined by combining pulse findings with clinical manifestations.
Tenth, the pulse of true cold must be slow, weak, and lacking spirit; the pulse of true heat must be slippery, forceful, and robust.
Eleventh, individuals with a Yang constitution tend to suffer from heat conditions, while those with a Yin constitution tend to suffer from cold conditions. Those with a Yang constitution invariably prefer cold drinks and fear heat; even if they consume cold food day and night without illness, this indicates an excess of Yang. Those with a Yin constitution will damage their Spleen and Kidney upon exposure to cold or cooling agents, indicating an insufficiency of Yang. However, those with strong Yang are few, comprising only two or three out of ten; those with weak Yang are many, comprising five or six out of ten. Yet, those who rely on their strength often fall ill, while those who fear weakness (and thus take care) remain healthy. If one envies another's strength while resenting one's own weakness, it is no different from a dwarf watching a performance or an ugly woman imitating Xi Shi holding her chest in pain.