Vs. Venom

"As predators, we have a glut of weapons in our physical arsenal — much, much more than really necessary. The strength, the speed, the acute senses, not to mention those of us like Edward, Jasper, and I, who have extra senses as well. And then, like a carnivorous flower, we are physically attractive to our prey." I was very still, remembering how pointedly Edward had demonstrated the same concept for me in the
meadow.
	She smiled a wide, ominous smile. "We have another fairly superfluous weapon. We're also venomous," she said, her teeth glistening. "The venom doesn't kill — it's merely incapacitating. It works slowly, spreading through the bloodstream, so that, once bitten, our prey is in too much physical pain to escape us. Mostly superfluous, as I said. If we're that close, the prey doesn't escape. Of course, there are always exceptions. Carlisle, for example."
	"So... if the venom is left to spread..." I murmured.
	"It takes a few days for the transformation to be complete, depending on how much venom is in the bloodstream, how close the venom enters to the heart. As long as the heart keeps beating, the poison spreads, healing, changing the body as it moves through it. Eventually the heart stops, and the conversion is finished. But all that time, every minute of it, a victim would be wishing for death."
	I shivered.
	"It's not pleasant, you see."
	"Edward said that it was very hard to do... I don't quite understand," I said.
	"We're also like sharks in a way. Once we taste the blood, or even smell it for that matter, it becomes very hard to keep from feeding. Sometimes impossible. So you see, to actually bite someone, to taste the blood, it would begin the frenzy. It's difficult on both sides — the blood-lust on the one hand, the awful pain on the other."
	"Why do you think you don't remember?"
	"I don't know. For everyone else, the pain of transformation is the sharpest memory they have of their human life. I remember nothing of being human." Her voice was wistful.