Why, Zombie, Why?

It's a lame thing to end my hiatus over, but I want to know what I'm missing.

1) Zombies are flesh-eating undead, always on the prowl for tasty people, and they especially like the brains.

2) Zombiehood is like the clap and can be acquired through any normal or abnormal exchange of bodily fluids.

So . . .

If a zombie devours my flesh, what is supposed to be left to turn into a zombie? Is there a simple answer to this, or do I need to start reading the massive and growing body of zombie fiction out there?

Give it to me straight.

R.