天之六气。春主厥阴风木。秋主阳明燥金。冬主太阳寒水。各行其政。惟夏至以后。秋分以前。
少阳相火。少阴君火。三气合行其事。是以天本热也。而益以日之暑。日本烈也。而载以地之湿。
三气交运。时分时合。其分也。以风动于中。胜湿解蒸。不觉其苦。其合也。天之热气下。地之湿气上。
人在气交之中。受其炎蒸。无隙可避。多有体倦神昏。肌肤痱起。胸膺痤出。头面疖生
者矣。当此之时。元气浮于肌表。内存者少。所以多有饮食不消。而成霍乱。吐泻胸膈不宽诸症。善养
生者。宜节饮食。薄滋味。为却病之良方。至于生冷瓜果。尤宜节制。西瓜虽能解热。食之亦必有时。
即如巳时申时。离饮食已远。新谷未进。食之毫不为殃。若饮食甫离。继以瓜果。势必冷热相抟。酿
成诸病也。内经曰。脉虚身热。得之伤暑。甲乙经曰。热伤气而不伤形。所以脉虚者是也。仲景分之为四。弦细芤
迟。皆为暑脉。总是元气虚衰之象。若难经所谓。洪大而散者。乃心之本脉。不可以言暑也。洁古云。
静而得之为中暑。动而得之为中热。此句最当领会。中暑者阴症也。凡乘凉于高堂大
厦。水阁冷亭。表受寒邪。周身阳气不得发越。以致头痛恶寒。身体拘急。脉来浮数滑大。即为夏月伤寒。
宜以寒法治之若脉来细缓无力。方为中暑。宜用香茹散暑汤。至于口食生冷。停滞饮食者。治分阴阳二候。
内热脉数。宜用柴胡化滞汤。脉沉细缓。宜用浓朴温中汤。香茹藿香以之为君。一则
发散阴暑。一则发越脾气。脾气宣行。积滞方得下降。不独治暑然也。但脉
缓者可用。脉数者不宜。若夫中热之症。行人农夫。日中劳役。或隘巷小房。无处乘凉。口鼻吸入
热气。以致身体大热。昏晕欲死。脉沉细数者。宜用辰砂六一散。或柴胡芍药汤之类。不可妄投热药。
大抵肥人多湿。最易召热。不能避身之湿。即不能避天之热。六一散。能驱湿热。从小便而出。
古人用之解暑有自来矣。若瘦弱无湿之人。津液为时令所耗。当用柴胡芍药汤。
藜汁蔗浆之类。充其津液。若用辰砂六一散。妄利小水。竭其下泉。枯槁立至。其有中热之人。脉洪盛
而不虚弱者。此天禀之浓。暑热客于肌肉。未得深入经络。身虽燥热。毫无倦怠。宜用竹叶石膏汤。
黄连解毒汤之类。不可与脉虚者。同归一治也。
天之六气，各自掌管时令：春季由厥阴风木主令，秋季由阳明燥金主令，冬季由太阳寒水主令，各行其政。唯独在夏至之后、秋分之前这段时间，少阳相火、少阴君火与湿土之气三气共同作用。因此，天气本已炎热，再加上日光的暑热；日光本已猛烈，又承载着地面的湿气。这三种气运交替运行，有时分开，有时合并。当它们分开时，风气在内部流动，胜除湿气并解除蒸热，人们不觉痛苦；当它们合并时，天的热气下降，地的湿气上升，人处于天地气交之中，受到炎热带蒸，无处可避，于是多有身体疲倦、精神昏沉，肌肤长出痱子，胸膺部位出现痤疮，头面部发生疖肿的情况。
在这个时候，人体的元气浮越于肌表，体内存留的元气较少，所以多有饮食不消化，从而形成霍乱，以及呕吐腹泻、胸膈部感觉不宽畅等各种症状。善于养生的人，应当节制饮食，减少厚味滋腻的食物，这是预防疾病的良方。至于生冷瓜果，尤其应该节制。西瓜虽然能解热，但食用也必须有适当的时间。就像巳时和申时，距离上一餐饮食已经很久，新的食物尚未进入胃中，此时吃西瓜丝毫不会带来祸害。如果刚吃完饭后，紧接着吃瓜果，势必导致冷热之气相互搏结，酿成各种疾病。
《内经》说：“脉象虚而身体发热，这是伤于暑邪所致。”《甲乙经》说：“热邪伤气而不伤形”，所以脉象虚就是这一表现。张仲景将暑病分为四种脉象：弦、细、芤、迟，这些都是暑病的脉象，总是元气虚衰的表现。如果像《难经》所说的“洪大而散”的脉象，那是心脏的本脉，不能用来描述暑病。李东垣（洁古）说：“静处而得病的是中暑，活动劳作而得病的是中热。”这句话最值得领会。中暑属于阴证，凡是乘凉于高大房屋、水阁冷亭等阴凉之处，体表受寒邪侵袭，周身阳气不能发散透达，以致头痛、恶寒、身体拘急疼痛，脉象浮数滑大，这就是夏季的伤寒，应当用寒凉法治之。如果脉象细缓无力，才是中暑，应当使用香薷散暑汤。至于因口食生冷、停滞饮食导致的病症，治疗要分阴阳两种情况。内热且脉数者，宜用柴胡化滞汤；脉沉细缓者，宜用浓朴温中汤。香薷、藿香作为君药，一方面发散阴暑，一方面发越脾气。脾气宣通运行，积滞才能下降，这不仅仅适用于治疗暑病。但是只有脉缓者可用，脉数者不宜。
至于中热的病症，行人农夫在烈日下劳役，或者在狭窄的小巷、小房中，无处乘凉，口鼻吸入热气，以致身体大热，昏晕欲死，脉象沉细数者，宜用辰砂六一散，或柴胡芍药汤之类。不可妄投热性药物。大抵肥胖的人多湿，最容易招致热邪，不能避开身体的湿气，也就不能避开天上的热邪。六一散能驱除湿热，从小便排出，古人用它来解暑是有来历的。如果是瘦弱无湿之人，津液被时令气候所耗损，应当用柴胡芍药汤、梨汁蔗浆之类，以补充其津液。如果使用辰砂六一散，妄行利尿，竭尽下焦肾水，枯槁之症立刻就会到来。那些患有中热的人，脉象洪盛而不虚弱者，这是先天禀赋浓厚，暑热客居于肌肉，尚未深入经络，身体虽然燥热，但毫无倦怠感，宜用竹叶石膏汤、黄连解毒汤之类，不可与脉虚者混为一谈，采用同样的治疗方法。
The Six Qi of Heaven each govern their respective seasons: Spring is governed by Jueyin Wind-Wood, Autumn by Yangming Dryness-Metal, and Winter by Taiyang Cold-Water, each exercising its authority independently. However, from after the Summer Solstice to before the Autumn Equinox, Shaoyang Ministerial Fire, Shaoyin Sovereign Fire, and Dampness combine to act together. Thus, the weather is inherently hot, further intensified by the sun's heat; the sunlight is inherently fierce, carrying with it the earth's dampness. These three qi interact and alternate, sometimes separating and sometimes merging. When they separate, wind moves within, overcoming dampness and resolving steaming heat, so that people do not feel suffering. When they merge, the heaven's hot qi descends, and the earth's damp qi ascends. Humans exist in the intersection of these qi, subjected to scorching heat and humidity with no place to hide. Consequently, many experience body fatigue and mental confusion, skin prickly heat (Feizi), acne on the chest and upper abdomen, and boils on the head and face.
At this time, the body's Yuan Qi (Original Qi) floats to the muscle surface, leaving less within the interior. Therefore, there are often cases of indigestion leading to Huoluan (Cholera-like syndrome), as well as symptoms such as vomiting, diarrhea, and a sensation of fullness or discomfort in the chest and diaphragm. Those skilled in nurturing life should regulate their diet and avoid rich, greasy flavors, which is an excellent prescription for preventing disease. As for raw, cold fruits and melons, one must especially exercise restraint. Although watermelon can resolve heat, it must be consumed at appropriate times. For instance, during the Si (9-11 AM) and Shen (3-5 PM) hours, when a long time has passed since the last meal and new food has not yet entered the stomach, eating it causes no harm. However, if one eats fruits immediately after a meal, the cold and hot energies will inevitably contend with each other, brewing various diseases.
The *Neijing* states: "Pulse deficiency and body heat result from injury by summerheat." The *Jia Yi Jing* states: "Heat injures Qi but does not injure Form," hence the pulse deficiency is indicative of this. Zhang Zhongjing divided summerheat into four types: Xian (Wiry), Xi (Fine), Kou (Hollow), and Chi (Slow) pulses are all summerheat pulses, representing the image of depleted Yuan Qi. If the pulse is described in the *Nan Jing* as Hong Da San (Surging, Large, and Scattered), this is the intrinsic pulse of the Heart and cannot be used to describe summerheat. Li Dongyuan (Jiegu) said: "Obtaining illness while resting is Zhongshu (Midsummer Heat); obtaining illness while moving/working is Zhongre (Midsummer Heat)." This statement is most worthy of comprehension. Zhongshu belongs to Yin syndromes. Whenever one seeks coolness in tall halls, pavilions, or cold terraces, the exterior is invaded by Cold Evil, causing the body's Yang Qi to fail to diffuse and emerge. This leads to headache, aversion to cold, and bodily stiffness/tension. With a pulse that is Fu Shuo Hua Da (Floating, Rapid, Slippery, and Large), it is considered Taiyang Cold Damage (Shanghan) of the summer months, and should be treated with Cold methods. If the pulse is Xi Huan Wu Li (Fine, Slow, and Weak), it is truly Zhongshu, and Xiangru San Shu Tang (Elsholtzia Decoction to Dispel Summerheat) should be used. Regarding illnesses caused by consuming raw/cold foods and stagnant digestion, treatment must distinguish between Yin and Yang presentations. Internal heat with a Shuo (Rapid) pulse calls for Chaihu Huazhi Tang (Bupleurum Decoction to Resolve Stagnation). A Chen Xi Huan (Deep, Fine, and Slow) pulse calls for Houpo Wenzhong Tang (Magnolia Bark Decoction to Warm the Middle). Xiangru (Elsholtzia) and Huoxiang (Patchouli) serve as the Sovereign herbs: one disperses Yin summerheat, the other promotes the ascending and descending function of Spleen Qi. Once Spleen Qi circulates freely, stagnation can descend. This applies not only to treating summerheat. However, this is suitable only for those with a Huan (Slow) pulse, not for those with a Shuo (Rapid) pulse.
As for Zhongre (Midsummer Heat) syndromes, pedestrians and farmers laboring under the midday sun, or those in narrow alleys and small rooms with no place to cool off, inhale hot qi through the mouth and nose. This results in severe body heat, fainting, and near-death sensations. With a pulse that is Chen Xi Shuo (Deep, Fine, and Rapid), Chen Sha Liu Yi San (Cinnabar Six-One Powder) or Chaihu Shaoyao Tang (Bupleurum and Peony Decoction) should be used. One must not recklessly administer Hot medicines. Generally, obese individuals have much Dampness and are most prone to attracting Heat. Inability to avoid bodily dampness means inability to avoid heavenly heat. Liu Yi San can drive out Damp-Heat via urination. The ancients used it to resolve summerheat for good reason. For thin, weak individuals without Dampness, whose Jin Ye (Body Fluids) are depleted by seasonal climate, Chaihu Shaoyao Tang, Pear Juice, or Sugarcane Juice should be used to replenish fluids. Using Chen Sha Liu Yi San would recklessly promote urination, exhausting the lower source (Kidney Water), leading to immediate emaciation and dryness. For those with Zhongre who have a Hong Sheng (Surging and Full) pulse without deficiency, this indicates strong innate constitution. Summerheat resides in the muscles and has not deeply penetrated the meridians. Although the body is dry and hot, there is no fatigue. Zhu Ye Shi Gao Tang (Bamboo Leaf and Gypsum Decoction) or Huanglian Jiedu Tang (Coptis Decoction to Resolve Toxicity) should be used. Such cases must not be treated identically to those with pulse deficiency.