张介宾曰病有两感于寒者一日则太阳与少阴表里俱病凡头痛发
热恶寒者邪在表口干而渴者邪在里二日则阳明与太阴表里俱病凡身热目痛鼻干不眠者邪
在
表腹满不欲食者邪在里三日则少阳与厥阴俱病几耳聋胁痛寒热而呕者邪在表烦满囊缩而厥水
浆不入邪在里凡两感者或三日或六日营卫不行脏腑不通昏不知人胃气乃尽故当死也拯救之计
但当辨其缓急或解其外或和其中或因虚固本使元阳不败孰先孰后临症酌宜不可鉴言方治也
两感者本表里之同病今见有少阴先溃于内而太阳继之于外即纵情肆欲之两感也太阴受伤于里
而阳明重感于表者即劳倦竭力饮食不调之两感也厥阴气逆于藏少阳复病于府者即七情不慎疲
筋败血之两感也
张介宾云合病者乃二阳三阳同病病之相合者也如初起发热恶寒头痛者此太阳之症而更兼
不眠即太阳阳明合病也若兼呕恶即太阳少阳合病若发热不眠呕恶者即阳明少阳合病也若三者俱全
便是三阳合病其病同故必辨其脉证犯何逆然后得以法而治其逆也
伤寒证以七日为一候仲景云太阳病头痛至七日以上自愈者以行其经尽故也即内经七日太
阳病衰头痛少愈之旨也喻昌云过经不解者由七八日以后至十三日已后病过一候二候犹不痊解也然
邪在身中日久势必结聚于三阳太阳为多少阳次之阳明又次之及至三阴则生死反掌不若此之久
张介宾说：病有“两感于寒”的情况，第一天就是太阳经与少阴经表里同时受病。凡是出现头痛、发热、恶寒的症状，说明邪气在表；凡是出现口干而渴的症状，说明邪气在里。第二天就是阳明经与太阴经表里同时受病。凡是出现身体发热、眼睛疼痛、鼻子干燥、无法入睡的症状，说明邪气在表；凡是出现腹部胀满、不想吃东西的症状，说明邪气在里。第三天就是少阳经与厥阴经同时受病。凡是出现耳聋、胁肋疼痛、寒热往来且呕吐的症状，说明邪气在表；凡是出现心中烦闷、阴囊收缩、四肢厥冷、水浆不能入口的症状，说明邪气在里。大凡属于两感病的，或者三天后死亡，或者六天后死亡，这是因为营卫之气运行停滞，脏腑气机不通，神志昏迷不醒，胃气耗尽，所以必然导致死亡。挽救救治的办法，只应当辨别病情的缓急，或者解除体表的邪气，或者调和内部的脏腑，或者因为正气虚弱而固护根本，使元阳不致败绝。至于先治表还是先治里，需根据临证情况斟酌适宜，不可拘泥于固定的方剂治疗。
所谓“两感”，本是表里两经同时发病。现在见到有少阴经先在内部溃败，随后太阳经在外部受邪的，这就是因纵情声色、肆意欲望导致的两感病。太阴经在内部受伤，随后阳明经再次感受表邪的，这就是因劳累过度、竭力劳作、饮食不调导致的两感病。厥阴经气机逆乱于内脏，少阳经又在腑脏发病的，这就是因七情不慎、疲劳筋骨、败坏血液导致的两感病。
张介宾又说：“合病”是指二阳或三阳经同时发病，是病邪相互合并的情况。比如初起时出现发热、恶寒、头痛的症状，这是太阳病的症状，如果再加上无法入睡，就是太阳病与阳明病合病。如果再加上呕吐恶心，就是太阳病与少阳病合病。如果既发热、无法入睡，又呕吐恶心，就是阳明病与少阳病合病。如果这三种症状全部具备，就是三阳合病。既然病症相同，就必定要辨别脉象和证候，判断犯了何种逆证，然后才能依据法则来治疗其逆证。
伤寒证的病程以七天为一个阶段（一候）。张仲景说：太阳病头痛，到了七天以上自愈的，是因为病邪在经脉中运行已尽的缘故。这也符合《内经》中“第七天太阳病衰退，头痛减轻”的宗旨。喻昌说：“过经不解”是指过了七八天以后，甚至到十三天以后，病情超过了一个阶段或两个阶段仍然没有痊愈解除。然而邪气在体内日久，势必会结聚在三阳经，其中太阳经受邪最多，少阳经次之，阳明经又次之。等到病邪传入三阴经，则生死变化就在顷刻之间，不像在三阳经那样持久。
Zhang Jiebin stated: There is a condition known as "Liang Gan Yu Han" (Two-Channel Cold Invasion), where the exterior and interior channels are simultaneously affected. On the first day, the Taiyang Channel (Greater Yang) and Shaoyin Channel (Lesser Yin) are both diseased in their respective exterior-interior relationship. Symptoms such as headache, fever, and aversion to cold indicate that the pathogen is at the exterior level; symptoms such as dry mouth and thirst indicate that the pathogen is at the interior level. On the second day, the Yangming Channel (Yang Brightness) and Taiyin Channel (Greater Yin) are both diseased. Symptoms such as body heat, eye pain, nasal dryness, and insomnia indicate that the pathogen is at the exterior level; symptoms such as abdominal fullness and loss of appetite indicate that the pathogen is at the interior level. On the third day, the Shaoyang Channel (Lesser Yang) and Jueyin Channel (Terminal Yin) are both diseased. Symptoms such as deafness, hypochondriac pain, alternating chills and fever, and vomiting indicate that the pathogen is at the exterior level; symptoms such as mental restlessness with fullness, retraction of the testicles, cold extremities, and inability to take in fluids or food indicate that the pathogen is at the interior level. In cases of Liang Gan, death may occur either after three days or six days because the Ying (Nutritive) and Wei (Defensive) Qi cease to circulate, the Zang-Fu organs become blocked, consciousness is lost, and the Stomach Qi is exhausted, leading inevitably to death. The strategy for rescue lies solely in distinguishing between urgency and slackness: one may release the exterior harmonize the interior, or tonify the root due to deficiency, ensuring that the Yuan Yang (Primordial Yang) does not collapse. Whether to treat the exterior or interior first must be judged according to clinical presentation; one should not rigidly adhere to specific formulas for treatment.
"Liang Gan" originally refers to the simultaneous disease of exterior and interior channels. Currently, there are cases where the Shaoyin Channel fails internally first, followed by the Taiyang Channel being affected externally; this corresponds to Liang Gan caused by indulgence in lust and desires. When the Taiyin Channel is injured internally, followed by repeated external contraction of pathogens into the Yangming Channel, this corresponds to Liang Gan caused by overexertion, labor, and irregular diet. When the Jueyin Channel experiences Qi rebellion within the Zang organs, and the Shaoyang Channel becomes diseased in the Fu organs, this corresponds to Liang Gan caused by imprudent emotional responses, physical fatigue damaging the sinews, and deterioration of the blood.
Zhang Jiebin further stated: "He Bing" (Combined Disease) refers to the simultaneous involvement of two or three Yang channels, representing the merging of pathological conditions. For instance, if initial symptoms include fever, aversion to cold, and headache, these are signs of Taiyang disease; if accompanied by insomnia, it constitutes a combination of Taiyang and Yangming diseases. If accompanied by vomiting and nausea, it constitutes a combination of Taiyang and Shaoyang diseases. If fever, insomnia, vomiting, and nausea all present together, it constitutes a combination of Yangming and Shaoyang diseases. If all three sets of symptoms are present, it is a Three-Yang Combined Disease. Since the pathological nature is similar, one must differentiate the pulse and syndromes to identify any rebellious patterns before applying appropriate therapeutic methods to correct the rebellion.
In the progression of Shanghan (Cold Damage) patterns, seven days constitute one period (Hou). Zhang Zhongjing stated: If Taiyang disease involving headache resolves spontaneously after seven days or more, it is because the pathogen has completed its course through the meridians. This aligns with the principle in the Neijing stating that on the seventh day, Taiyang disease declines, and headaches subside slightly. Yu Chang stated: "Guo Jing Bu Jie" (Pathogen Passing the Meridian Without Resolution) refers to conditions persisting beyond seven or eight days, up to thirteen days or more, where the illness exceeds one or two periods without resolving. However, when pathogens remain in the body for an extended time, they inevitably aggregate in the Three Yang channels, with Taiyang being most susceptible, followed by Shaoyang, and then Yangming. Once the pathogens reach the Three Yin channels, life and death can change in an instant, unlike the prolonged course observed in the Yang channels.