DOCTOR: What are you holding? Show me. Friend. Doctor, Donna. Friend. Let me see. Look at me. Let me see. That's it. That's it, go on. Go on.

(The Ood opens his hands. He is holding a small brain.)

DONNA: Is that?

DOCTOR: It's a brain. A hind brain. The Ood are born with a secondary brain. Like the amygdala in humans, it processes memory and emotions. You get rid of that, you wouldn't be Donna any more. You'd be like an Ood. A processed Ood.

DONNA: So the company cuts off their brains?

DOCTOR: And they stitch on the translator.

DONNA: Like a lobotomy. I spent all that time looking for you, Doctor, because I thought it was so wonderful out here. I want to go home.

HALPEN: They welcomed it. It’s not as if they put up a fight.

DONNA: You idiot. They’re born with their brains in their hands. Don’t you see, that makes them peaceful. They’ve got to be, because a creature like that would have to trust anyone it meets.