风寒在表，舌多无苔，即有白苔，亦薄而滑；渐传入里，方由白而黄，由黄而燥，由燥而黑。
瘟疫一见头痛、发热，舌上即有白苔，且浓而不滑；或色兼淡黄；或粗如积粉。若传经入胃，则兼二、三色，
又有白苔即燥与至黑不燥者。大抵疫邪入胃，舌苔颇类风寒，以兼湿之故而不作燥耳。惟在表时，舌苔白浓，
异于伤寒。能辨于在表时，不用辛温发散，入里时，而用清凉攻下，斯得矣。
时疫传里之后，蓄血最多，治从攻里，兹不具论。惟本有内伤停瘀，复感时疫，于初起一、二日，疫之表证悉
具，而脉或芤、或涩，颇类阳证阴脉，但须细询其胸、腹、胁肋、四肢，有痛不可按而濡者，即为蓄血确验，
其芤、涩非阳证见阴脉，乃表证见里脉也。治法必兼消瘀，红花、桃仁、归尾、赤芍、元胡之类，量加一、二
味，表邪方易解，涩、芤之脉方易起。若误认芤、涩为阴脉，而投温剂，轻者变剧，重者危矣。
时疫较之风寒，本为难治，以风寒传变有次序，时疫传变无常经；风寒表邪，一发即散，时疫散而复集，且往
往复之再三；风寒传里证，一攻即和，时疫攻而复合，有下至一、二十次者，此时疫之难治也。
而脾虚者更为难治。盖时疫必得汗下而后解，脾虚者，表不能作汗，里不任攻下。或得汗矣，而气随汗脱；
得下矣，而气从下脱。治此等证，汗勿强汗，发表必兼养正，人参败毒散是也；下勿轻下，攻里必兼固气、生津
液，黄龙汤是也。其外证无大分别，惟脉不任寻按。然邪有进退，当其邪进方张之时，脉亦有寻按有力者，不可泥
也，必合气、色、神、情、脉证以相参。如面色萎黄，神情倦怠，气息微促，及心悸、耳鸣皆脾虚中气不振之象，
更须通体合参。如通体皆见有余实象，而独见一、二虚象，则虚象反为吃紧；通体见虚象，而独见一、二实证，
则实证又为吃紧。总须权衡标、本，凡证之属表、属上焦、属六腑者，皆为标；证之属里、属中焦、下焦、属五
脏，皆为本。若实证居标，虚证居本，则虚证为重；虚证居标，实证居本，则实证为重。到此虚实关头，
必着意参详，庶几无失。
风寒邪气在体表时，舌头上大多没有苔；即使有白苔，也是薄而滑润的；病邪逐渐传入体内后，舌苔才由白色转为黄色，由黄色转为干燥，由干燥转为黑色。
瘟疫病一见头痛、发热，舌上立即出现白苔，而且厚腻不滑润；或者颜色兼带淡黄；或者粗糙像堆积的粉一样。如果病邪传经进入胃腑，则舌苔会兼见二种或三种颜色，
又有舌苔白而干燥，以及直到变黑也不干燥的情况。大抵疫邪进入胃腑，舌苔的表现颇类似风寒病，只是因为兼夹湿邪的缘故所以不表现为干燥罢了。只有在表证阶段，舌苔白且厚腻，
这与伤寒病是不同的。能在表证阶段辨别清楚，在表证时不用辛温发散的方法，等到病邪入里时，改用清凉攻下的方法，这样就对了。
时行疫病传入体内之后，蓄积瘀血的情况最多，治疗应当从攻逐里实入手，这里不再详细论述。只是对于原本就有内伤停瘀的人，又感染了时行疫病，在发病初起的一两天，疫病的表证全部具备，
而脉象或者是芤脉（浮大中空，如按葱管）、或者是涩脉（往来艰涩，如轻刀刮竹），很像阳证见到阴脉，但必须仔细询问其胸、腹、胁肋、四肢，如果有疼痛且拒按、触之柔软无硬块的情况，就是蓄血的确实证据，
这种芤脉、涩脉并不是阳证见到阴脉，而是表证见到反映里证的脉象。治疗方法必须兼顾消除瘀血，加入红花、桃仁、当归尾、赤芍、延胡索之类的药物，酌情加一两种，表邪才容易解除，涩脉、芤脉才容易恢复。如果误认芤脉、涩脉为阴脉，而投用温补药剂，轻的病证会变严重，重的病证就会危及生命。
时行疫病比起风寒病，本来就更难治疗，因为风寒病的传变有一定的次序，时行疫病的传变没有固定的经络规律；风寒在表的邪气，一经发汗就散去了，时行疫病则是散了又聚集，并且反反复复多次；
风寒传入体内的证候，一经攻下就能调和，时行疫病则是攻下后又复合，有的甚至攻下了一二十次，这就是时行疫病难治的原因。
而对于脾虚的患者来说，更是难治。因为时行疫病必须通过发汗和攻下才能解除，脾虚的人，肌表不能作汗，体内不能承受攻下。或者虽然发了汗，但气随汗液外脱；
或者虽然攻下了，但气从下部脱失。治疗这类证候，发汗不要强行发汗，发表时必须兼顾扶助正气，人参败毒散就是这样的方子；攻下不要轻易攻下，攻里时必须兼顾固护元气、生津液，黄龙汤就是这样的方子。这类患者的外在证候没有太大区别，只是脉象不耐重按。然而邪气有进退变化，当邪气正盛的时候，脉象也有重按有力的情况，不可拘泥不变，必须结合气色、神情、脉证相互参照。比如面色萎黄，神情倦怠，气息微弱短促，以及心悸、耳鸣，都是脾虚中气不振的表现，更需要全身综合参详。如果全身都表现出有余的实证象，唯独出现一两个虚证象，那么虚证象反而成为关键；全身表现虚证象，唯独出现一两个实证象，那么实证象又成为关键。总之必须权衡标与本的关系，凡是属于表证、属于上焦、属于六腑的证候，都称为标；凡是属于里证、属于中焦、下焦、属于五脏的证候，都称为本。如果实证位于标位，虚证位于本位，那么虚证为重；虚证位于标位，实证位于本位，那么实证为重。到了虚实的关键关头，
必须着重仔细参详，这样才能不出差错。
When Wind-Cold pathogen is in the Exterior, the tongue usually has no coating; even if there is a white coating, it is thin and slippery. As the pathogen gradually transmits to the Interior, the coating changes from white to yellow, from yellow to dry, and from dry to black.
In Plague (Yi Wen), upon the appearance of headache and fever, a white coating appears on the tongue immediately, which is thick and not slippery; or the color is mixed with pale yellow; or it is coarse like accumulated powder. If the pathogen transmits through the meridians into the Stomach, the coating may present two or three colors simultaneously.
There are also cases where the white coating is dry, or turns black without becoming dry. Generally, when the epidemic pathogen enters the Stomach, the tongue coating resembles that of Wind-Cold, but due to the presence of Dampness, it does not become dry. The key distinction lies in the Exterior stage: the white coating is thick,
which differs from Shang Han (Cold Damage). By distinguishing this at the Exterior stage, one should not use Acrid-Warm Diaphoresis (Xin Wen Fa San) for the Exterior, but rather employ Cooling and Purging methods once the pathogen enters the Interior; this approach ensures success.
After the seasonal plague transmits to the Interior, blood stasis accumulates significantly, and treatment follows the principle of purging the Interior, which will not be discussed in detail here. However, for patients who already have internal injury with stagnant blood and subsequently contract the seasonal plague, during the first one or two days of onset, all exterior symptoms of the plague are present,
yet the pulse may be Khong (Floating, large, and hollow, like pressing a green onion stalk) or Se (Rough and choppy, like a light knife scraping bamboo), resembling a Yang syndrome presenting with a Yin pulse. One must carefully inquire about pain in the chest, abdomen, hypochondrium, and limbs that cannot be pressed and feels soft upon palpation; this is definitive evidence of blood stasis.
The Khong and Se pulses here do not represent a Yin pulse appearing in a Yang syndrome, but rather an Interior pulse appearing in an Exterior syndrome. The treatment method must include resolving blood stasis by adding herbs such as Hong Hua (Carthami Flos), Tao Ren (Persicae Semen), Gui Wei (Radix Angelicae Sinensis Caulis), Chi Shao (Radix Paeoniae Rubra), and Yuan Hu (Rhizoma Corydalis), selecting one or two ingredients in appropriate doses. Only then can the Exterior pathogen be easily resolved, and the Se and Khong pulses easily restored. If the Khong and Se pulses are mistakenly identified as Yin pulses and warm tonifying agents are administered, mild cases may worsen, and severe cases may become critical.
Seasonal plague is inherently more difficult to treat than Wind-Cold because Wind-Cold transmission follows a specific sequence, whereas seasonal plague transmission occurs without fixed meridian patterns. Wind-Cold pathogens in the Exterior dissipate immediately after diaphoresis, while plague pathogens disperse only to reaggregate, repeatedly multiple times.
Wind-Cold interior syndromes harmonize after a single purgative intervention, whereas plague interior syndromes tend to recur after purgation, sometimes requiring one or twenty purgations; this is why seasonal plague is difficult to treat.
Patients with Spleen Deficiency are even more difficult to manage. Seasonal plague requires both sweating and purging to resolve, but patients with Spleen Deficiency cannot sweat effectively from the Exterior and cannot tolerate purgatives in the Interior. Even if sweating occurs, Qi may collapse following the sweat;
even if purgation occurs, Qi may collapse from below. In treating such cases, forced sweating should be avoided; when releasing the Exterior, one must concurrently support Zheng Qi (Upright Qi), using Ren Shen Bai Du San (Ginseng and Imperata Decoction) as an example. Light purgation should be avoided; when purging the Interior, one must concurrently secure Qi and generate body fluids, using Huang Long Tang (Yellow Dragon Decoction) as an example. The external manifestations of these cases show little difference, except that the pulse is not resilient to pressure. However, pathogens advance and retreat; when the pathogen is advancing and vigorous, the pulse may still feel forceful upon pressure, so one must not adhere rigidly to this sign. It is essential to integrate Qi, complexion, spirit, demeanor, and pulse signs. For instance, sallow complexion, listlessness, weak and rapid breathing, palpitations, and tinnitus are all signs of Spleen Deficiency with failure of Middle Qi to rise; comprehensive assessment of the whole body is necessary. If the whole body presents excess signs but one or two deficiency signs appear, the deficiency signs become critical; if the whole body presents deficiency signs but one or two excess signs appear, the excess signs become critical. Ultimately, one must weigh Biao (Branch/Surface) and Ben (Root/Origin). Syndromes belonging to the Exterior, Upper Jiao, or Six Fu Organs are considered Biao; syndromes belonging to the Interior, Middle Jiao, Lower Jiao, or Five Zang Organs are considered Ben. If excess resides in the Biao and deficiency in the Ben, the deficiency is heavy; if deficiency resides in the Biao and excess in the Ben, the excess is heavy. At this juncture of deficiency and excess,
careful deliberation is required to avoid error.