That gets him a much longer, assessing stare - or at least, as long as Jack can give whilst being hauled along by a raptor, which isn't very. He's still trying to find an angle to pierce its touch hide whilst dodging the long and pointed beak that's trying to turn and snap at him when Spike manages to grab it and bite it instead. Rather than being repulsed as some might be, Jack laughs, still clinging to it to try and help hold it still enough to let Spike do his thing. He has no idea if a vampire bite will be enough to kill it, but even if it doesn't, it's distracted the creature long enough for him to finally get his knife in between the scales and do some actual damage.