Zevachim 43: Preventing Karet by Preventing Piggul

We began learning a new Mishna in daf 42 and it continues in today's daf:

• usually we are not liable for karet if we eat a damaged offering
• exceptions, says Rabbi Meir:
• an item permitted for consumption/the altar by another item
• handful of flour that permits eating the meal offering
• meal offering of priests
• the meal offering of the anointed priest
• the incense and the frankincense
• the blood which permits the offerings
• the libations brought as a separate offering
• The Rabbis argue:
• libations brought with an animal offering as well
• the log of oil brought with the guilt offering of a recovered leper
• regarding any item has permitting factors for consumption by a person or for burning at the altar, on is liable for eating it as it is prohibited by piggul prohibitions
• the blood of the burnt offering permits the flesh to be burned on the altar
• the bird burnt offering's blood permits its flesh and skin to be burned on the altar
• the bird sin offering's blood permits its meat for consumption by the priests
• bulls and goats burnt for unwitting communal sins (of idol worship, for goats) blood permits their sacrificial portions to be sacrificed on the altar
• Rabbi Shimon asserts that the blood of the above offerings are not brought to the the outer altar like a peace offering, and so one is not liable for eating them as they have not violated the laws of piggul

The Gemara begins with a conversation about the kometz, the handful of flour, oil and incense.  It permits the consumption of the offering.  It also permits the priestly offering which burns entirely on the altar.  That kometz and the priests' offering serve as insurance: The offerings cannot become piggul, and if eaten, one is not liable for karet.  For much of their later discussions, the rabbis focus on the meaning of ritual impurity and how that definition might change the consequences of one's acts of sacrifice.