פירוש על בבא קמא 4:3

The Sages taught: three primary categories. The Gemara asked a question: do the derivatives of damagers have the same laws as the avos? Now, the Gemara introduces a lengthy Braita that explains all the avos of shor and how they are derived. It seems as if the Gemara forgot to answer the question. Tosafot explains:
The Gemara interrupted its flow by citing this Braita, so that eventually he can explain, using this Braita as a basis, which are their toldos that are not like the avos, of which Rav Papa spoke.