Kelim, Chapter Nineteen, Mishnah Ten
1) A dung-basket that was so damaged that it will not hold pomegranates:
a) Rabbi Meir says is still susceptible to uncleanness,
b) But the sages say that it is clean because if the primary function ceases the secondary one also ceases.
The mishnah deals with a “dung-basket,” a basket used to take out dung used for fertilizer. If the basket has a hole large enough for pomegranates to escape, then the basket then it can’t be used as a dung-basket (it would make some serious mess on the floor).
Rabbi Meir says that since it can still be used as a seat cushion, it is still susceptible to impurity.
The other sages disagree, invoking the principle we saw in yesterday’s mishnah. If something can no longer be used for its primary purpose (to carry dung) then it is no longer susceptible, even if it can be used for a secondary one.