Bava Kamma 23: Is the Mouth of a Cow Like the Courtyard of an Injured Party?

The rabbis discuss a fire that destroys a courtyard.  In some instances, it is as if this is similar to his arrows.  In other instances, it is as if his arrows are depleted - he caused the fire within his own courtyard, but he was not responsible for the fire in a neighbouring courtyard.  Continuing their discussion of a dog who steals cake with a hot coal stuck to it which starts a fire in a stack of grain, the rabbis consider unusual iterations of that case.  One detail is whether or not the damaged items were properly safeguarded against fire.

This leads the rabbis to a discussion of how "the mouth of a cow is like the courtyard of an injured party".  In such a case, the owner of the dog who sets fire to the grain can say, "What is your cake doing in my dog's mouth?"  The dog's mouth is the property of its owner, and the owner is not liable for damage done to another person's property while that property is in the owner's domain.  If the animal caused damage by rubbing itself on the owner's property, damages can be paid.  

The example of a hand is shared: if a person is damaged by the teeth of an animal on their own property, but the the person's hand never enters the dog's mouth, the owner of the dog is not liable.  Only if the damage is done inside the dog's mouth is the owner liable; the dog's mouth is the dog owner's property and thus damage is done on his property.

The rabbis discuss incitement.  If one incites a snake and the snake bites, he is liable to pay the damages.  This may not be the owner of the snake but any other person.  The rabbis believe that there are certain actions that animals do that cannot be trained away.  An animal is not stoned, otherwise killed or punished for actions that it must perform.  Animals cannot be slaughtered to prevent them from damaging people or things.  

Our daf ends with a new Mishna about an ox that is innocuous, tam, or forewarned, mu'ad.  Rabbi Yehuda says that an ox is mu'ad if witnesses say that it gored on three days and it becomes tam again when it does not gore for three consecutive days.  Rabbi Meir says that it is mu'ad if it gores on any three days and that is is tam again when children can pet it and play with it without being gored.

The Gemara begins its exploration of this Mishna by discussing the notion of days.  What are these consecutive days?  What does 'yesterday' or 'the day before yesterday' refer to?  And what does this suggest about an owner who has not secured his ox even after it has gored once?