Ever notice, how many movie cowboys, particularly the good guys, get shot in the shoulder? It's incredible, here is this large body mass and invariably that piece of lead finds it's way to the shoulder, more often than not, the left shoulder. In that area is a large junction of nerves branching from the spinal column, which controls the muscles and function of the arm. It is called the brachial plexus. I remember many years ago, my anatomy professor lecturing on this plexus of nerves and stating that everyone was born with this anatomy except cowboys because, when shot in this region, there never seemed to be any lasting damage.