Bekhorot 33: three things to remember

Beit Hillel permit any ritually impure person, including a menstruating woman, to eat the meat of a blemished firstborn.
A disqualified offering cannot be flayed from the feet because preserving the hide tears the flesh and reduces value.
The Rabbis allow bloodletting a congested firstborn to save it, but prohibit slaughtering it based on any resulting blemish.