Today a professor went on a tangent during an otherwise boring lecture and showed us how to percuss our hearts to determine where its borders are. That woke most of us up a little, because it sounded more interesting than the extracellular matrix. He had us all try it on ourselves while he demonstrated, and I was pretty pleased to really hear the difference between the hollow space and my heart.
I was less pleased when I realized I had been watching him so carefully that I was percussing the right-hand side of my chest.
Action Potential 
maybe you have dextrocardia… I’d like to order a CXR… haha