if you look right in between this kind of a valley and the reason is that this impact site is swollen. this is swollen here. this is not swollen. you know there are two separate impacts. one impact here and one impact here with an area in between that's not swollen. the swollen is bleeding under the scalp. >> the knot or the lump that people get after hitting their head on something hard is blood as opposed to some other fluid? >> it's blood. a medical term is hematoma but a knot is non-medical. >> talk about the curvature of