Bava Kama 52: Good Enough for an Ox, But Not for a Camel

A pit and its passersby - where one person covers a cistern, the next person does not...who's liable? And at what point is the owner's covering of the pit recent enough to make him exempt from paying damages? What happens if a pit is open because it is being expanded, and the noise of the construction startles an ox so it falls into it - the owner will be liable (or not), depending on which direction it falls in. If the animal falls on the vessels it is carrying, then the owner of the put is not liable for that damage. Plus, an ox that is a deaf-mute, cognitively impaired, or a minor... Also, if an ox breaks through a damaged cover to a pit... Is the owner of the pit liable, or was the ox just unexpectedly heavy? What if the cover works to protect an ox from falling through, but doesn't protect camels, is the owner negligent? Also, why are the camels in the Gemara here, but not the mishnah? Could the case cover all animals, or is that too much to expect?