A baheres the size of a gris is surrounded by living skin [the width] of a lentil, and [another] baheres is outside the living skin — the inner one is confined and the outer one is confirmed. Said R’ Yose: The michyah is not a symptom of tumah for the outer [nega] since a baheres is inside it. [If the michyah] receded, or disappeared, Rabban Gamliel says: If it diminished on the inner side, it is a sign of expansion for the inner [nega], and the outer [nega] becomes tahor. But if [it diminished] from the outer side, the outer [nega] becomes tahor and the inner [nega] shall be confined. R’ Akiva says: Either case is tahor.

Said R’ Shimon: When [is this true]? When it is exactly [the size of] a lentil; [if] it was larger than a lentil, the extra area is a symptom of expansion for the inner [nega], and the outer one is tamei. [If] it contained a dull white blemish smaller than a lentil, it is a symptom of expansion for the inner one, but not for the outer one.