How we cite our quotes: Act.Scene
Quote #1
Cam. …Your silkworm used to fast every third day, and the next following spins the better. To-morrow at night, I am for you. (1.2)
Camillo is using this insincere excuse to avoid sleeping with his wife. Essentially, he's saying he's not a sex machine—he needs time to recharge his batteries. But he doesn't actually plan on following through the next day—he's too busy fighting pirates or whatevs.
Quote #2
Isab. I do beseech you,
Entreat him mildly, let not your rough tongue
Set us at louder variance; all my wrongs
Are freely pardon'd; and I do not doubt,
As men to try the precious unicorn's horn
Make of the powder a preservative circle,
And in it put a spider, so these arms
Shall charm his poison, force it to obeying,
And keep him chaste from an infected straying. (2.1)
The straying is "infected" because Brachiano might pick up some STDs whle sleeping around. Isabella wants to charm him and re-direct his lust back towards her—but it's too late. The fix is in, and she's gonna die.