Kelim, Chapter Eleven, Mishnah Seven
1) A curved horn is susceptible to impurity but a straight one is clean.
2) If its mouthpiece was covered with metal it is unclean.
3) If its broad side [is covered with metal]:
a) Rabbi Tarfon says it is susceptible to impurity
b) But the sages say it is clean.
4) While they are joined together the whole is susceptible to impurity.
5) Similarly: the branches of a candlestick are clean.
a) And the cups and the base are susceptible to impurity,
b) But while they are joined together the whole is susceptible to impurity.
Section one: A curved horn (perhaps a type of shofar, although some explain this to be a wood instrument) is susceptible to impurity because it contains a receptacle in which it would be possible to receive liquids. But the straight one is not susceptible, as is the rule with vessels made of bone or wood.
Section two: If parts of the horn are covered with metal, it may be susceptible to impurity. If the mouthpiece is covered with metal, it is considered a metal vessel and is susceptible whether or not it is curved.
Section three: There is a debate over whether the straight horn is susceptible if its broader side is covered with metal. According to Rabbi Tarfon, this is sufficient to turn it into a metal vessel, whereas the sages say that it is not. Only if the mouthpiece is covered with metal is it susceptible.
Section four: If the mouthpiece is joined together with the broad side, making one seamless whole, then if any part is susceptible, it is all susceptible.
Section five: Similar rules apply to a candlestick. Its branches are not susceptible when they are separated from the whole, because they do not have their own names. The cups and base are susceptible because they contain receptacles. But if they are all joined together, all of the parts are susceptible.