A baheres the size of a gris contains living skin the size of a lentil. [If] it covers him completely and then the living skin disappears, or if the living skin disappears and then [the nega] covers him completely, [the afflicted person] is tahor. [If] living skin appeared [in a completely expanded nega], he is tamei. [If] white hair appeared on it, R’ Yehoshua renders it tamei, and the Sages render it tahor.

A baheres with white hair that [subsequently] covered him completely is tahor, even though the white hair remains. A baheres that expanded [and subsequently] covered him completely is tahor. All of these [cases] become tamei if the extremities return. [If] it spread partially, he is tamei; [if] it covered him completely, he is tahor.