Nazir 16: A Contradiction in a Nazir's Terms

A new chapter! And 2 new mishnayot. Opening with the case of one who takes a vow of becoming a nazir, but without specifying the number of days - as compared to one who does articulate "30 days," and what happens when each person shaves his head on the 30th day. What about a vow that sets up two periods of nezirut, to be consecutive. When does shaving become acceptable? Plus, what are the implications with regard to his becoming impure? Also, the case of one who takes the vow to be a nazir while in a cemetery - the count can't start until he's left the cemetery and become pure to begin with.