Two players share a deck composed of three cards: Jack, Queen, and King. The highest card wins. You each ante one. You each get a card. The third card remains unseen. There's one standard round of betting, with a max bet of one chip each, giving the following choices: the first player can check or bet one. Player two can call, fold, check or raise one (as appropriate). If needed, player one can then call or fold (no re-raising).

Today, trepanation, or drilling a hole in the head, is commonly used to release the pressure of swelling inside the skull.

Throughout history, it's been used to treat epilepsy, migraines, mood disorders and pretty much any other head condition that seemed to surgeons of the time as if it could be improved by seeing the light of day. But even more interesting than holding someone down and punching a hole through his/her skull is doing it yourself.

As promised, here's part three of the nails-in-the-brain trilogy. Only, while nails may be the brain-poking standby, they're not the only foreign bodies to be shot, shoved or stabbed into the human brain.

For example, after getting into a fistfight a man reported to his local emergency room with a headache, black eye and a cut on his cheek. Imaging found a 10.5-centimeter paintbrush embedded in the man's brain. Surgery removed the paintbrush and the man experienced no lasting effects. The paintbrush had entered bristles-first.

Yesterday I posted a couple splendid instances of people driving nails into their brains. And here, for those of you that think (as I do) that the only thing better than nails-in-the-brain stories is MORE nails-in-the-brain stories, are a couple more. Stay tuned tomorrow for things other than nails that've been surgically removed from brains of the unfortunate.

Here are a couple wonderful instances of people accidentally or intentionally driving nails deep into their gray matter. Can't get enough nails in the brain? Don't worry—I'll post another couple tomorrow.

Look at a waterfall for 30 seconds. Now look at something stationary. The stationary object will appear to drift upwards. The same phantom movement is true after stepping off an airport walkway: if you close your eyes and stand still, you should continue to feel yourself moving.