夫气盛者，夏酷暑而不热，冬严寒而不冷，此里实而寒暑不能侵之也。禀气弱者，未寒
先寒，未热先热，故未有十日天寒，日阴则感寒湿而濡泻，未有十日天温，日明则伏热而中
，虚弱之人常态也。盖先知节气者，能辨阴阳寒暑出入之盛衰。《素问》云∶阳盛人能冬
不能夏，阴盛人能夏不能冬。此亦人之虚实与寒暑相为否泰者矣。且立夏气变纯阳，万物茂
盛，用药者用热远热，如桂枝麻黄大青龙汤，并诸热药，必加知母升麻石膏辈，是不尽其热
药也。且立冬两阴俱尽，气合纯阴，用药者用寒远寒，如服诸凉剂，服汤利过者止后服，不
必尽剂，是不尽用凉药也。是寒月不尽用凉药，若尽用凉药，表里皆寒，人不能当故也。治
疮疹亦当根据此，随虚实寒温，阴阳出入而用药也，岂可拘一证一药为尽而已矣。病患素有盛
实，或素有虚者，并用古方，不在加减尔。且春分阳渐在外，而阴渐在内，秋分阳渐在内，
而阴渐在外，用药者岂得而同诸？此按四时阴阳，迎合脏腑内外虚实而用之，故时当阳出而
阴入，则实者愈，阴出而阳入，则虚者愈，故阳出而阴入者虚者病，阴出而阳入者实者病，
此其常理不变者也。如冬温虚者安而实者病，夏寒则实者安而虚者病，此皆节气阴阳虚实使
之也。冬温暖，夏寒凉，非节气为病者，在人将摄而可尔。所以钱氏治疮痘，言春夏顺而秋
冬逆者，是论阴阳出入迎合表里之意也。
那些元气旺盛的人，在夏天酷热时不觉得热，在冬天严寒时不觉得冷，这是因为体内充实，外来的寒暑邪气无法侵入。禀赋元气虚弱的人，还没到寒冷的时候先感到寒冷，还没到炎热的时候先感到炎热。所以，如果连续十天天气寒冷、阴天，就会感受寒湿之邪而患腹泻；如果连续十天天气温暖、晴朗，就会因伏热内蕴而发病，这是虚弱之人的常态。大概先知节气变化的人，能够辨别阴阳寒暑盛衰出入的规律。《素问》说：阳气盛的人能耐受冬天而不能耐受夏天，阴气盛的人能耐受夏天而不能耐受冬天。这也是人的虚实体质与寒暑气候相互影响、导致顺逆不同的道理。况且立夏时节，气候变为纯阳之气，万物茂盛生长，用药者应当“用热远热”（使用热性药物要避开炎热的季节），比如桂枝汤、麻黄汤、大青龙汤以及诸般热性药物，必须加入知母、升麻、石膏这类药物，这样就不能算作纯粹的热药了。况且立冬时节，两阴之气俱尽，气候合为纯阴之气，用药者应当“用寒远寒”（使用寒性药物要避开寒冷的季节），比如服用诸般凉剂，如果服用汤药后利下过多就应停止后续服药，不必服完全部剂量，这就是不完全使用凉药的道理。所以在寒冷的月份不完全使用凉药，如果完全使用凉药，会导致表里皆寒，人不能承受的缘故。治疗疮疹也应当依据这个原则，根据虚实寒温、阴阳出入的情况来用药，怎么能拘泥于一种证候和一种药物就认为穷尽了治法呢？病患平素体质偏盛实，或平素体质偏虚弱的，都直接应用古方，不需要加减化裁。况且春分时节，阳气逐渐向外发散，阴气逐渐向内收敛；秋分时节，阳气逐渐向内收敛，阴气逐渐向外发散，用药者怎么能一概而论呢？这是按照四时阴阳的变化，迎合脏腑内外的虚实情况来用药，所以当阳气外出而阴气入内时，实证患者会痊愈；当阴气外出而阳气入内时，虚证患者会痊愈。因此，阳气外出而阴气入内是虚证患者的病理表现，阴气外出而阳气入内是实证患者的病理表现，这是不变的常理。比如冬天气候温暖，虚证患者安逸而实证患者患病；夏天气候寒冷，实证患者安逸而虚证患者患病，这都是节气阴阳虚实变化所导致的。如果是冬天异常温暖、夏天异常寒冷，并非由正常节气引起的疾病，在于人们调养得当就可以避免。所以钱乙治疗疮痘时说春夏顺应（阳气）而秋冬逆反（阳气），这是论述阴阳出入迎合表里的意思。
Those with abundant Qi do not feel hot in the intense heat of summer, nor cold in the severe cold of winter; this is because their interior is solid, preventing the invasion of cold and heat pathogens. Those with weak constitutive Qi feel cold before it becomes cold, and feel hot before it becomes hot. Thus, if the weather remains cold and cloudy for ten days, they may contract cold-dampness leading to loose stools (Ru Xie); if the weather remains warm and sunny for ten days, latent heat may cause internal disorder. This is the normal state of those with weak constitutions. Generally, those who understand solar terms can distinguish the flourishing and decline, entry and exit of Yin, Yang, cold, and heat. The *Su Wen* states: "Those with Yang excess can endure winter but not summer; those with Yin excess can endure summer but not winter." This illustrates how human deficiency or excess interacts with cold and heat climates to produce favorable or unfavorable outcomes. At the beginning of Summer (Li Xia), the climate shifts to pure Yang, and all things flourish. When prescribing, one should "avoid heat when using hot remedies" (Yong Re Yuan Re). For instance, Guizhi Tang (Cinnamon Twig Decoction), Mahuang Tang (Ephedra Decoction), Da Qing Long Tang (Major Green Dragon Decoction), and other hot medicines must be combined with Zhi Mu (Anemarrhenae Rhizoma), Sheng Ma (Cimicifugae Rhizoma), and Shi Gao (Gypsum Fibrosum). In doing so, they are no longer purely hot medicines. At the beginning of Winter (Li Dong), both Yin energies are exhausted, and the qi combines into pure Yin. When prescribing, one should "avoid cold when using cold remedies" (Yong Han Yuan Han). For example, when taking various cooling agents, if diarrhea occurs excessively after taking the decoction, subsequent doses should be stopped without completing the full prescription. This means not fully utilizing cold medicines. Therefore, in cold months, one does not fully use cold medicines; if one did, the exterior and interior would both become cold, which the body cannot withstand. Treating variola (Chuang Zhen) should also follow this principle, adjusting medications according to deficiency/excess, cold/warmth, and the entry/exit of Yin/Yang. How can one rigidly adhere to a single syndrome and a single herb as the ultimate treatment? Patients with chronic excess or chronic deficiency should simply use ancient formulas without modification. At the Spring Equinox, Yang gradually moves outward while Yin gradually moves inward; at the Autumn Equinox, Yang gradually moves inward while Yin gradually moves outward. How can medication be applied uniformly? This involves aligning with the four seasons' Yin and Yang, accommodating the interior/exterior and deficiency/excess of the Zang-Fu organs. Thus, when Yang exits and Yin enters, excess syndromes resolve; when Yin exits and Yang enters, deficiency syndromes resolve. Therefore, "Yang exiting and Yin entering" characterizes deficiency diseases, while "Yin exiting and Yang entering" characterizes excess diseases; this is the unchanging constant principle. For example, in a warm winter, deficiency patients are comfortable while excess patients fall ill; in a cold summer, excess patients are comfortable while deficiency patients fall ill. These are all caused by the changes in solar terms, Yin/Yang, and deficiency/excess. If winter is abnormally warm or summer abnormally cold—conditions not dictated by normal solar terms—one can avoid illness through proper self-care. Therefore, when Qian Yi treated variola, stating that spring and summer follow the norm while autumn and winter reverse it, he was discussing the meaning of Yin/Yang entry/exit and its accommodation of the exterior and interior.