This isn't so much gross as horrifying, but when my dad was in high school, he played football. He was hit so hard in the head that his vision looked like the negatives for film photos.

The coach slapped him on the back, told him he was fine, and that he should get back out there. Yeah. Sounds like an awesome plan when your player probably has some kind of concussion.

That's only happened to him once after that - when he was struck by lightning a year or so ago.
If a brain specialist ever looks at my Dad's brain, he will probably be horrified by all the concussive damage Dad has sustained and amazed that Dad's maintained an above - average quality of life.
Also, if any of you have ever pulled on your finger so hard it felt like the joint came apart, that's what happened to me last night...in my lower back. I almost cried.