A large animal is acquired by mesirah, and a small one by being lifted; [these are] the words of R’ Meir and R’ Eliezer. The Sages, however, say: A small animal is acquired by meshichah.

Possessions which can have a lien on them are acquired with money, with a document, or with an act of possession, and [those] which cannot have a lien on them are acquired only with meshichah.  Possessions which cannot have a lien on them are acquired together with possessions which can have a lien on them with money, with a document, or with an act of possession; and possessions which cannot have a lien on them cause [one] to swear concerning possessions which can have a lien on them.