夫渴者，邪热入脏津液枯竭，而脏腑精华不足也。故四五六日之间而渴者，是邪已
传阴分，理之所宜。若一二三日间，尚在三阳传变而渴者，理之所逆，盖里既热甚，而
表症未罢，是谓两感。如表症既退而渴者，是邪尽入于里也。便结便须下之，以去其热
邪。若两感者，宜和解之。若素不竭，而药
后乃渴者，是水气散，阳气复，里气温，故渴也。故渴者，当至不渴，不渴者，当至微
渴为愈，均平阴阳之义也。然伤寒以思饮水为欲愈。若不与则不愈。若恣饮又恐水停，
故宜少饮之，再思再与。若六脉洪数，重按久按有力，果系实症阳症，方可与以新汲凉
水，否则恐有上热下寒者，便忌误服寒冷矣。
凡有物有声者，谓之呕。有声无物者，为之干呕。无声有物者，谓之吐。如内觉烦
燥，睡卧不宁，吐酸而呕者，热气逆于胃也。吐白水者，寒邪客于胃也。饮水即呕
者，水停心下也。吐蛔者，胃中虚冷也。如汗出遍体，自腰以下独无而呕者，是津液不
得下行，热气上逆而致也。如呕吐而又发热者，此是半表半里之症，然吐中便有发散之
义。若吐后表热益甚者，则邪乘虚入胃矣。如食后而即吐者，此胃气与邪相争而然。然
胃气未脱，名曰小逆。如反能食，胸胀烦燥，时时酸气上行，既不能化又不能吐者，
是邪气胜胃，不能与邪相搏，名曰火逆。若在病愈之后，呕吐不了者，是因汗下太过，
阳明胃虚耳，治宜温胃。
所谓口渴，是因为邪热侵入脏腑，导致津液枯竭，脏腑的精华不足。因此，在发病后的第四、五、六天出现口渴，说明邪气已经传入阴分，这是符合病理规律的。如果在第一、二、三天之间，病邪还在三阳经传变时就出现口渴，这属于反常情况；这是因为体内热势极盛，而表证尚未解除，这种情况称为“两感”（表里同病）。如果表证已经消退而出现口渴，说明邪气完全入里。此时大便干结，就必须使用攻下法，以清除体内的热邪。如果是“两感”的情况，适宜采用和解法治疗。如果患者平时并不口渴，服药后才出现口渴，这是因为水湿之气消散，阳气恢复，里气温和，所以感到口渴。因此，口渴的症状应当发展到不再口渴，或者不渴时仅有轻微口渴才算痊愈，这是阴阳平衡的道理。然而，伤寒病中，病人想要喝水是病情即将痊愈的表现。如果不给饮水，病就不会好。但如果让病人随意大量饮水，又担心水饮停滞体内，所以应该少量多次地给予饮水，即病人想喝时就再给一点。如果六脉洪大且数，重按久按时有力，确实是实证、阳证，才可以给予新汲取的凉水，否则恐怕有上热下寒的情况，就会忌讳误服寒冷之物了。
凡是既有声音又有呕吐物的，称为“呕”。只有声音没有呕吐物的，称为“干呕”。没有声音但有呕吐物的，称为“吐”。如果自觉心中烦躁，睡眠不安，泛酸并伴有呕吐，这是热气逆乱于胃所致。吐出白水，是寒邪客居在胃所致。喝水后立即呕吐，是水饮停滞在心下（胃脘部）所致。吐出蛔虫，是胃中虚冷所致。如果全身出汗，唯独腰部以下不出汗并伴有呕吐，这是津液不能下行，热气上逆所导致的。如果呕吐并且伴有发热，这是半表半里的症状，然而呕吐本身就具有发散邪气的意义。如果呕吐后表热更加严重，则是邪气乘虚侵入胃腑。如果进食后立即呕吐，这是胃气与邪气相争的结果。此时胃气尚未脱失，称为“小逆”。如果反而能进食，胸部胀满烦躁，时常有酸气上行，既不能消化又不能吐出，这是邪气胜过胃气，胃气不能与邪气抗争，称为“火逆”。如果在病愈之后，仍然呕吐不止，是因为发汗或攻下太过，导致阳明胃气虚弱，治疗宜温补胃气。
Thirst refers to the depletion of body fluids and insufficiency of the essence of the Zang-Fu organs due to pathogenic heat entering the viscera. Therefore, thirst occurring between the fourth and sixth days indicates that the pathogen has transmitted to the Yin aspect, which is consistent with pathological principles. If thirst occurs within the first three days while the pathogen is still transforming among the Yang meridians (Taiyang, Yangming, Shaoyang), it is considered contrary to normal progression; this is because internal heat is severe while exterior symptoms have not yet resolved, a condition termed "Liang Gan" (simultaneous involvement of exterior and interior). If thirst appears after the exterior symptoms have subsided, it signifies that the pathogen has fully entered the interior. In cases where constipation is present, purgation should be employed to eliminate the pathogenic heat. For "Liang Gan," harmonization is appropriate. If a patient who was previously not thirsty becomes thirsty after taking medication, it indicates that damp-fluids are dissipating, Yang Qi is recovering, and the interior warmth is returning, thus causing thirst. Consequently, for thirst to resolve, it should progress to a state of no thirst, or only slight thirst when not actively drinking, reflecting the principle of balancing Yin and Yang. However, in Cold Damage diseases, the desire to drink water indicates impending recovery. Withholding water will prevent recovery. Yet, allowing unrestricted drinking may lead to fluid retention; therefore, small amounts of water should be given repeatedly as desired. If the six pulses are surging and rapid, and firm upon deep and prolonged pressure, indicating a true Excess or Yang pattern, fresh cool water may be administered. Otherwise, caution must be exercised against cold substances, as patterns of upper heat and lower cold may exist.
Vomiting accompanied by sound and matter is called "Ou". Vomiting with sound but no matter is called "Gan Ou" (dry heaving). Vomiting with matter but no sound is called "Tu". If one feels inner irritability, restless sleep, acid regurgitation, and vomiting, it is due to heat qi rebelling in the Stomach. Vomiting clear watery fluid indicates cold pathogen lodging in the Stomach. Vomiting immediately after drinking water suggests fluid retention in the epigastrium ("Xin Xia"). Vomiting roundworms indicates deficiency-cold in the Stomach. If sweating covers the whole body except below the waist, accompanied by vomiting, it results from body fluids failing to descend and heat qi rebelling upward. If vomiting is accompanied by fever, it represents a Half-Exterior Half-Interior syndrome; however, vomiting itself possesses a dispersing function. If exterior heat worsens after vomiting, the pathogen has entered the Stomach due to deficiency. Immediate vomiting after eating indicates a struggle between Stomach Qi and the pathogen; if Stomach Qi remains intact, it is termed "Minor Reversal" (Xiao Ni). If the patient can eat despite chest distension and irritability, with frequent rising of sour gas, unable to digest or vomit, it is because pathogenic factors overpower the Stomach Qi, preventing it from struggling against the pathogen; this is called "Fire Reversal" (Huo Ni). If vomiting persists after the illness has seemingly resolved, it is due to excessive sweating or purgation leading to deficiency of the Yangming Stomach Qi; treatment should focus on warming the Stomach.