宣白承气汤之“宣白”识

Understanding of "Xuanbai" in Xuanbai Chengqi Decoction

宣白承气汤证是邪热壅滞于上焦肺,致使肺气无法下达,肠腑无法顺承所致,自当降肺气,使大肠得以"顺承"肺胃之气,腑气通畅而司传导,这也是方名中"承气"的内涵。换言之,此时病理机制的主要矛盾是肺气不通,而矛盾的主要方面则是肺失肃降,治疗时针对矛盾的主要方面,故而降肺气即所以通肺气。宣白承气汤中吴鞠通之所以用杏仁、石膏"宣肺气之痹",是因为肺气因邪热壅滞而痹阻不能下行,这里的"宣"也当理解为疏通,"宣白"也即疏通肺气,这样才符合吴鞠通本意。疏通肺气有别于"宣肺",适用于肺气宣和(或)降的功能失调所致之肺气不通。故吴鞠通之宣白承气汤清肺热、降肺气、通腑气,当是为疏通肺、胃、大肠之气机而设,如其自辨所言是"宣肺气之痹"而非"宣肺","宣"是疏通之意,"宣白"当理解为疏通肺气,如此则医理通,疑惑除。

Syndrome of Xuanbai Chengqi Decoction（ XBCQD） means that pathogenic heat obstructs in the lung so that lung qi cannot go down smoothly to the large intestine. Therefore,lung qi should be descended to make the large intestine connect qi from the lung and stomach. Smooth visceral qi guarantees transmission,which is just the connotation of ＂ Chengqi＂ in the decoction. In another word,the main contradiction of the pathological mechanism is lung qi obstruction,and the main aspects of the contradiction is the lung failing to descend,therefore,the treatment should focus on descending lung qi which means unobstructing lung qi.In XBCQD,the WUs uses Xingren（ Semen Armeniacae Amarum） and Shigao（ Gypsum Fibrosum） to unobstuct lung qi which cannot move down due to pathogenic heat obstructing in the lung. Here, ＂ Xuan＂ can be understood as unobstructing,and ＂ Xuanbai＂ means unobstructing lung qi,which is the purpose of the WUs. Unobstructing lung qi is different from ＂ dispersing the lung＂,and it refers to obstructed lung qi due to the lung failing to disperse and descend. Therefore,XBCQD focuses on clearing lung heat,descending lung qi,unobstructing qi of the large intestine,and is designed to unobstruct qi activities of the lung,stomach and large intestine,just as it means ＂ unobstructing lung qi＂ but not ＂ dispersing the lung＂. So ＂ Xuan＂ means unobstructing; ＂ Xuanbai＂ means unobstructing lung qi. In this way,a reasonable understanding of it is clear without any doubt.