He thinks Australia is still a little too close to Antarctica, but his argument dies and he considers his hand, or more specifically, horrifically, his left-hand ring finger, before he says, "You know me, dude. Always game for science. So," he places the edge of his right hand over the farthest knuckle on his left-hand pinky, almost a cutting motion, then over the middle knuckle, and finally at the joint connecting the pinkie to his hand, "how big of a slice do you need?"

Of course, Newt wants to know why a severed finger is required, but he trusts Hermann. The why has no bearing on the question of if he is willing. Of course he is willing. It's science. It's Hermann. Why is simply his own curiosity. Hermann had a yes from the moment he breathed Newton's name.