A baheres the size of a gris contains living skin the size of a lentil, and on the living skin there is white hair. If the healthy skin disappeared, [the baheres] is tamei because of white hair. [If] the white hair fell out, [the baheres] is tamei because of living skin. R’ Shimon considers it tahor because the baheres did not cause [the hair] to change color. A baheres, and the living skin it contains, together equal the size of a gris, and there is white hair inside the baheres. [If] the living skin disappeared, it is tamei because of the white hair. [If] the white hair fell out, it is tamei because of the living skin. R’ Shimon considers it tahor because [the hair] was not changed by a baheres the size of a gris. However, he agrees that if there is a gris [of nega] where the white hair [grows], it is tamei.

A bahereshad both living skin and an expan-sion. [If subsequently] the living skin disappeared, [the nega] is [still] tamei because of expansion. [If] the expansion disappeared, [the nega] is [still] tamei because of living skin. The same rule applies to white hair and to expansion. [If the nega] went away and returned at the end of the week, it is treated as if it remained unchanged. [If the nega went away, and returned] after it was declared tahor, it is examined anew. If [the nega] was bright and became dull, [or it was] dull and became bright, it is treated as if it remained unchanged, as long as it does not become less [bright] than the four shades. If [the nega] contracted and then expanded, [or] it expanded and then contracted, R’ Akiva renders it tamei, and the Sages render it tahor.

A baheres the size of a gris expanded by half a gris, but half a gris of the original baheres disappeared. R’ Akiva says: It must be examined anew, and the Sages render it tahor.

A baheres the size of a gris expanded more than half a gris, but half a gris of the original baheres disappeared, R’ Akiva renders it tamei, and the Sages render it tahor. A baheres the size of a gris expanded by more than a gris, but the original baheres disappeared. R’ Akiva renders it tamei, and the Sages say: It must be examined anew.