Finishing out the 7th chapter, about the blemishes among human beings: kohanim need to commit to not making themselves come in contact with a dead body. How is that different from marrying a person who is prohibited to the kohanim? And starting the 8th chapter — on the process of redeeming the first-born son — in the new mishnah! Or rather, there are different statuses for which one may or may not be called the first born, such as the inheritance and also for the kohen. With some complicated cases about premature births. Also, defining the moment of birth — when the forehead emerges, even if the rest of the body hasn’t followed yet. Including the case of a woman who was converting during the process of delivering the baby, and she is non-Jewish when the forehead emerges and Jewish when the rest of the baby emerging. And identifying that child (or any person, it seems), is as per one’s face, from the forehead to including the nose (or perhaps before the nose).