The basic diagnostic and treatment principles of traditional Chinese medicine are the pattern-differentiation-deduced pathogenesis and treatment based on examination of the pathogenesis.Shanghan Lun established a system of pattern differentiation of six meridians,systematically summarized the evolution laws of exogenous febrile disease,and discussed miscellaneous diseases as exogenous diseases.It contains 112 classic formulas and advocates that"those whose disease corresponds to the formulas should take them accordingly",combining disease differentiation and pattern differentiation,containing not only the knowledge of treatment based on pattern identification,but also the profundity of pattern-differentiation-deduced pathogenesis.Based on the original meaning of"pathogenesis",from the three angles of"subtle meaning","core meaning",and"appropriate meaning",this paper exemplifies the concept of pattern differentiation for six meridians in Shanghan Lun,analyzes the relationship and connotation of formula patterns of classical formulas in Shanghan Lun by"taking pattern with formulas",and explores the concept of pattern-differentiation-deduced pathogenesis in Shanghan Lun.This paper emphasizes that during the clinical practice of traditional Chinese medicine,it is important(i)to deduce the pathogenesis based on pattern differentiation,understand symptoms upon first onset,and deduce the pathogenesis before symptoms appear,thereby treating the disease at an early stage;(ii)to identify the most important concepts,solve complications with simple method,discern the core of the disease,and treat the entire body;and(iii)to optimize timing,act quickly,take advantage of opportunities,accept outcomes,and provide judicious guidance to patients.This paper serves to interpret Shanghan Lun based on pattern-differentiation-deduced pathological mechanism and provides ideas and inspiration for applying the theory of Shanghan Lun to guide clinical practice.

Dong qi,referring to beating beside the navel,was proposed for the first time by Nan Jing."Beating above the navel""beating below the navel",and"beating below the heart"in Shanghan Lun all belong to the category of Dong qi.The pathogenesis of Dong qi can be learned from Shanghan Lun.Yang deficiency of the heart,spleen,and kidney,with qi failing to transform body fluids,results in fluid retention.Fluid retention is the key etiological factor of Dong qi.Although there is an exterior pattern with Dong qi,the exterior-releasing and purgative method cannot be used for treatment,or the patient will be impaired of yang and exhausted of yin,fluid circulation will be disturbed,and so on.Reinforcing yang qi to drain water retention is the treatment principle of Dong qi.The coupled medicines of Fuling and Guizhi were commonly used by ZHANG Zhongjing to treat Dong qi.This reflects the treatment principle of strengthening the spleen and warming yang for transforming qi to circulate body fluids.ZHANG Bi,a physician from the Yuan Dynasty who learned from ZHANG Zhongjing,thought that the treatment of Dong qi was based on the method of cultivating earth to restrain water and taking into account the ascending,descending,entering,and exiting of qi of the liver,heart,lung,and kidney while tonifying the spleen,and then created Baoming Siqi Powder(Zhiqiao,Fuling,Fangkui,and Qianhu Powder)for the treatment of Dong qi,which is of great significance to the clinic.