Take a AA battery. Lick your fingers. Hold the positive with your thumb and the negative with your index finger. You have now completed the circuit. I guarantee you won't feel like you did.
Most musicians have tested used 9v
batteries with our tongues to evaluate voltage when an effects pedal goes down on stage and there's not a new 9v battery in the gig bag! It's a buzz, but only momentarily. The one with the strongest sensation gets used. Back in the day, we didn't have cheap VOM's or battery testers available, so we kept used ones in a zip lock bag to get
through the night sometimes.
I finally wised up and started keeping a brand new 9V in the gig bag!