Identifying the study subject, "to be in meridian or collateral", is the first step of meridian-collateral differentiation. Combined with the ancient literature and clinical practice of acupuncture and moxibustion, the methods of identifying "to be in meridian or collateral" and its values are elaborated. Through analyzing the onset location of symptoms and the body layers of lesions, as well as the palpation and observation in meridian-collateral detection, "to be meridian" or "to be collateral" is identified in disease diagnosis. It may guide the choice of techniques of acupuncture and moxibustion. Identifying "to be meridian or collateral" is crucial in meridian-collateral differentiation, which not only contributes to improving the therapeutic effect of acupuncture and moxibustion, but also to better recognizing diseases and understanding the relevant concepts of techniques of acupuncture and moxibustion in view of acupuncture and moxibustion, and perfecting the system of meridian-collateral differentiation.
以经络辨证的第一层次——辨“在经在络”为研究对象，结合古代文献和针灸临床实际，对辨“在经在络”的方法及其意义进行系统阐述，发现通过分析病症表现之发病部位、病变层次和经络诊察之切诊、望诊，可以辨别疾病是“在经”或是“在络”，进而可指导刺灸法的选择；经络辨证首辨“在经在络”不仅有利于提高针灸疗效，而且对于在针灸视域下更好地认识疾病、理解刺灸法相关概念、健全完善经络辨证体系等均具有重要意义。.
Keywords: collateral disorder; differentiation of acupuncture and moxibustion; meridian disorder; meridian-collateral differentiation.