Our Mishna deals with the application of the laws of a shor tam – an ox with no known violent tendencies. The Torah teaches (Shemot 21:35) that when an ox gores another ox and kills it, both the live animal and the dead one are sold and their value is divided between the owner of the ox that did the damage (the mazik) and the owner of the ox that was killed (the nizak). This is the source for the idea that we have already seen, that a shor tam pays hatzi nezek mi-gufo – half of the damage that it did, but not more than its own value.
The Mishna illustrates this law with the following example:
If an ox that is worth 200 gores an ox that is also worth 200, and the carcass of the dead animal has no value, both the mazik and the nizak will receive 100 – half the value of the shor tam that gored. Rabbi Meir comments that this is the archetypical case discussed in the Torah (Shemot 21:35). Rabbi Yehuda objects that in this case we divide the value of the animal that gored, but not of the dead animal. According to Rabbi Yehuda, the archetypical case is one where the goring ox was worth 200 and the ox that was killed was worth 200, and the carcass was worth 50. In this case, each party would receive 125, according to the Torah’s rules.
The Gemara asks why Rabbi Meir and Rabbi Yehuda argue – after all they are both in agreement that the mazik and nizak would each receive 125 in Rabbi Yehuda’s case. Rava suggests that the difference is who would lose out in a situation of pehat nevelah – where the value of the carcass becomes worth less over time. According to Rabbi Meir, the carcass belongs to its original owner, and if it loses value, the loss is his. Rabbi Yehuda believes that the two parties become partners in both animals, and if the value of the carcass drops, they will share the loss.
When an animal is killed, the value of the carcass is established based on the price of the (non-kosher) meat and the animal’s hide. As time passes and the natural processes of decomposition set in, the value of the animal will drop. The difference in value from the time of death to the time that the animal is sold is what the Gemara refers to as pehat nevelah.