An employee was lowering a pallet when the pneumatic cylinder that was holding the pallet malfunctioned. The cylinder did not release the pallet. The employee walked down the stairs of the platform to the lower level and unplugged the hose of the cylinder. When he released the air, it activated the ram of the cylinder. His hand was positioned between the frame work of a metal dumper and the ram of the cylinder. The employee pulled his hand out. His left index finger was amputated at the first joint.