The phrases “it is difficult to continue” (相続也大難) and “the blood lineage is not interrupted” (血脈不断) are found in the Biyan lu 碧巌録, one of the most important works of gong’an Chan 公案禅 during the Song dynasty. These phrases came from the sayings of two patriarchs of the Cao-Dong 曹洞 lineage, Dongshan Liangjie 洞山良价 and Caoshan Benji 曹山本寂. There is a possibility that these phrases had been passed down in the traditions of the Cao-Dong lineage. These phrases show that, when interpreting gong’an, the Biyan lu had a tendency to show an appreciation of monks changing their positions constantly and developing questions and answers without interruption. In this interpretative perspective, emphasis is placed on skillfully preserving the flow of dialogue, and individual phrases of a gong’an are not interpreted on the basis of their inherent meaning. This is one of the reasons that the Biyan lu is difficult to understand.