Zevahim 80: Neither Add Nor Subtract from the Mitzvah

A long mishnah that begins on daf 79b: More on mixtures of blood - first, that of an animal with no blemish with that of an animal with a blemish. Which necessitates spilling that mixture down the drain. But the cases here recognize the difference between what is ideal and what needs to be tolerated, or is considered acceptable once it has already been done. Which moves the discussion to the question of placing blood in 4 places or only 1 place on the altar - which some of the blood needs the 4 places, and some the 1, which turns into a dispute over "bal tosif" vs. "bal tigra" -- adding or suppressing to the mitzvah. Also, the Gemara discusses a parallel mishnah - where the dispute is about a blemished limb, rather than this mixture issue. Plus, whether these mixtures work to "blend" -- and when can you cover your bases?