INJURED WAS THROWING THE SWITCH AT #3 HEAD WHEN THE INCIDENT OCCURRED. PART OF THE SWITCH DID NOT THROW. INJURED REACHED DOWN TO PULL PART OF THE SWITCH THAT DIDN'T THROW WHEN IT FLEW BACK AND PINNED HIS LEFT THUMB AND INDEX FINGER, BETWEENTHE RAILS. THE SWITCH WAS SPRING LOADED. A CO-WORKER ASSISTED INJURED IN FREEZING HIS HAND. SUFFERED INJURIES TO LEFT THUMB AND INDEX FINGER.