伤寒两感者，阴阳双传也，虽为必死之证，犹有可救之理。盖用药先后，发表攻里，本自不同。
《活人书》先救里以四逆汤，后攻表以桂枝汤。殊不知仲景云∶太阳与少阴病，头疼恶寒，邪在表；
口干而渴，邪在里。阳明与太阴病，身热目痛，邪在表；不欲食，腹满，邪在里。少阳与厥阴病，
耳聋胁痛，寒热而呕，邪在表；烦满囊缩，邪在里。三阳之头痛，身热，耳聋胁痛，恶寒而呕，在
表者，已自不可下之。其三阴之腹满，口渴，囊缩谵语，在里者，可不下乎？《活人书》引下利身
疼痛，虚寒救里之例，而欲施治于烦满囊缩，实热之证，可乎？盖仲景所谓
发表者，葛根、麻黄是也。攻里者，调胃承气是也。《活人书》却谓救里则是四逆，攻表则是桂枝。
今以救为攻，岂不相悖？若用四逆，是火济火，而腹满，囊缩等证何由而除？脏腑何由而通？荣卫
何由而行？故死者，可立而待也。学人岂可执一定之法于胸中乎？
合病并病，世所难明，若非得其精专，焉能识此证哉！合病者，两经或三经齐病不传者，为合
病。并病者，一经先病未尽，又过一经之传者，为并病。若并而未尽，是传未过，尚有表证，法当
汗之。若并之已尽，是为传过，法当下之。是知传则入腑，不传不入腑，言其有传受如此也。三阳
互相合病，皆自下利，太阳阳明合病，主葛根汤；太阳少阳合病，主黄芩汤；少阳阳明合病，主承
气汤。三阳合病无表证者，俱可下。但三阳经合病，仲景无背恶寒语句。虽则有口燥渴，心烦，背
微恶寒者，乃属太阳证而非三阳合病也。三阳若与三阴合病，即是两感，所以三阴无合并例也。
伤寒两感证，是指阴阳两经同时受邪传变。虽然这属于预后极差的危重证候，但仍有救治的可能。这是因为用药的先后次序、解表与攻里的治法，原本就有区别。
《活人书》主张先用四逆汤（回阳救逆方）救治里证，后用桂枝汤（解肌发表方）攻治表证。殊不知张仲景指出：太阳经与少阴经同病时，头痛、恶寒，说明邪气在表；口干而渴，说明邪气在里。阳明经与太阴经同病时，身热、目痛，说明邪气在表；不欲饮食、腹部胀满，说明邪气在里。少阳经与厥阴经同病时，耳聋、胁痛、寒热往来且呕吐，说明邪气在表；烦躁胀满、阴囊收缩，说明邪气在里。三阳经病的头痛、身热、耳聋胁痛、恶寒呕吐等表现，既然邪气在表，本来就不可以使用下法。至于三阴经病的腹满、口渴、阴囊收缩、胡言乱语等表现，既然邪气在里，难道可以不使用下法吗？《活人书》引用“下利、身疼痛”这种虚寒证需要急救里证的先例，却想将其施用于“烦满、囊缩”这种实热证，这合适吗？
张仲景所说的“发表”，指的是使用葛根、麻黄这类药物。“攻里”，指的是使用调胃承气汤（缓下热结方）。《活人书》却说救里用四逆汤，攻表用桂枝汤。现在把“救里”当作“攻表”来用，岂不是相互矛盾？如果在这种情况下使用四逆汤，无异于火上浇油，那么腹满、囊缩等症状如何能消除？脏腑功能如何能通畅？营卫之气如何能运行？因此，死亡是可以立刻等待到的结果。学习中医的人，怎么可以心中执着于一种固定的治疗方法呢？
合病和并病，世人很难明白，如果不是精通此道，怎么能识别这些证候呢！合病，是指两经或三经同时发病而不互相传变的，称为合病。并病，是指一经的病邪尚未痊愈，又传入另一经的，称为并病。如果是并病且病邪未完全传入，说明传变尚未完成，还有表证存在，治法应当采用发汗法。如果是并病且病邪已完全传入，说明传变已完成，治法应当采用攻下法。由此可知，传变则病邪入腑，不传变则不入腑，说的是病邪有传变的情况如此。
三阳经互相合病，都会出现下利症状。太阳经与阳明经合病，主方用葛根汤；太阳经与少阳经合病，主方用黄芩汤；少阳经与阳明经合病，主方用承气汤。三阳经合病且没有表证的，都可以使用下法。但是，在三阳经合病的条文中，张仲景并没有提到“背恶寒”的症状。虽然有口燥渴、心烦、背部轻微恶寒的情况，那属于太阳经证，而不是三阳经合病。如果三阳经与三阴经合病，那就变成了两感伤寒，所以三阴经没有合并症的例子。
Taiyang-Shaoyin simultaneous infection (Lianggan Shanghan) refers to the simultaneous transmission of pathogenic factors into both Yin and Yang meridians. Although this is considered a critical condition with a poor prognosis, there remains a possibility of rescue. This is because the sequence of medication administration and the distinction between releasing the exterior and purging the interior are fundamentally different.
The *Qianjin Yifang* (Book of Vitality) advocates first rescuing the interior with Sini Tang (Four Reversal Decoction), and subsequently attacking the exterior with Guizhi Tang (Cinnamon Twig Decoction). However, it fails to realize that Zhang Zhongjing stated: In Taiyang-Shaoyin simultaneous disease, headache and aversion to cold indicate the pathogen is in the exterior; dry mouth and thirst indicate the pathogen is in the interior. In Yangming-Taiyin simultaneous disease, fever, eye pain, and discomfort indicate the pathogen is in the exterior; anorexia and abdominal fullness indicate the pathogen is in the interior. In Shaoyang-Jueyin simultaneous disease, deafness, hypochondriac pain, alternating chills and fever, and vomiting indicate the pathogen is in the exterior; irritability, fullness, and retraction of the genitals indicate the pathogen is in the interior. For the headaches, fever, deafness, hypochondriac pain, aversion to cold, and vomiting associated with the Three Yang meridians, since the pathogen is in the exterior, purgative methods should inherently not be used. Conversely, for the abdominal fullness, thirst, genital retraction, and delirium associated with the Three Yin meridians, since the pathogen is in the interior, can one refrain from using purgatives? The *Qianjin Yifang* cites the precedent of "diarrhea with body ache," a deficiency-cold pattern requiring urgent interior rescue, and attempts to apply this treatment to "irritability, fullness, and genital retraction," which are excess-heat patterns. Is this appropriate?
Zhang Zhongjing's concept of "releasing the exterior" refers to herbs such as Gegen (Kudzu Root) and Mahuang (Ephedra). His concept of "purging the interior" refers to Tiaowei Chengqi Tang (Stomach-Regulating Major Purge Decoction). Yet, the *Qianjin Yifang* claims that rescuing the interior requires Sini Tang and attacking the exterior requires Guizhi Tang. To treat "rescuing the interior" as "attacking the exterior" is contradictory. If Sini Tang is used in this context, it is akin to adding fuel to fire. How will symptoms like abdominal fullness and genital retraction be resolved? How will the Zang-Fu organs become unobstructed? How will Ying and Wei Qi circulate? Consequently, death may occur immediately. How can practitioners rigidly adhere to a single fixed method in their minds?
Simultaneous disease (Hebing) and overlapping disease (Bingbing) are difficult for the world to comprehend. Without profound expertise, how can one recognize these patterns? Simultaneous disease occurs when two or three meridians are affected simultaneously without sequential transmission. Overlapping disease occurs when the pathogen of one meridian has not fully resolved before transmitting to another. If the overlap is incomplete, transmission is not yet finished, and exterior signs remain, the treatment principle is diaphoresis (sweating). If the overlap is complete, transmission has finished, the treatment principle is purgation. Thus, transmission implies entry into the Fu organs, while no transmission implies no entry into the Fu organs, describing the nature of transmission.
When the Three Yang meridians mutually combine, diarrhea often ensues. For Taiyang-Yangming simultaneous disease, Gegen Tang (Kudzu Decoction) is the primary formula. For Taiyang-Shaoyang simultaneous disease, Huangqin Tang (Scutellaria Decoction) is the primary formula. For Shaoyang-Yangming simultaneous disease, Chengqi Tang (Purge Decoction) is the primary formula. When Three Yang simultaneous disease presents without exterior signs, purgation is applicable. However, in Zhang Zhongjing's discussions on Three Yang simultaneous disease, there is no mention of "aversion to cold in the back." Cases involving dry mouth, thirst, irritability, and slight aversion to cold in the back belong to Taiyang syndrome, not Three Yang simultaneous disease. If the Three Yang meridians combine with the Three Yin meridians, it becomes Lianggan (simultaneous Yin-Yang infection); therefore, there are no examples of combination solely within the Three Yin meridians.