Question: Our Mishnah teaches four Avos Nezikin, and R. Chiya taught 13 - [these four, and] Nezek (lifelong loss in earning potential due to a blow), pain, medical expenses, Sheves (inability to work while recovering), embarrassment; a Shomer Chinam (one who guards a deposit for free), a borrower, a Shomer Sachar (he is paid to guard it), and one who rents an object.

Answer: Our Mishnah taught only Hechsher Nezikin (one's property, which he enabled to damage through not guarding it). R. Chiya taught both Hechsher Nezikin and damage from his own body.

Question (R. Chagai): How did our Mishnah teach four Avos Nezikin? If all [Avos] found in an ox are counted as one, it should teach three (the others are a pit and fire). If all found in an ox are counted as three (Keren, Shen and Regel), it should teach five!

Answer: The way the verses speak, so our Mishnah speaks. (Keren is taught by itself, and Shen and Regel are together in one verse.)

Toldos of Keren are goring, Negifah (pushing with the horns), biting, crouching, kicking, and Dechiyah (pushing with the body).

Question (R. Yitzchak): Goring and Negifah are primary (Avos, for they are explicit in the Torah), and you call them Toldos?!

Answer: Rather, he begins with the primary (Avos) and concludes with Toldos.

Toldos of a pit - the entire third Perek of Nezikin (our tractate, it teaches them).

Rebbi taught that if one placed a coal in Reshus ha'Rabim, and one came and tripped on it, and he had a flask in his hand, if his clothes were burned and his flask broke, [the one who placed the coal] is liable for the flask due to a pit, and for the clothes due to fire.

Toldos of Regel - it was taught that if an animal entered Reshus ha'Yachid and damaged, whether with its forelegs, hind legs, horn, the yoke on it, the load on it, or the wagon it is pulling, it pays full damage. And one who damages in Karmelis pays full damage. (SEDEI YEHOSHUA - it is for Peros, and not for animals.)