Sore (saw) Head!!!

Stan and John were scrapping cars, with a stihl saw, and John cut his arm off. Stan wrapped the arm in a plastic bag and took it and John to a surgeon. The surgeon said, "You're in luck! I'm an expert at reattaching limbs! Come back in four hours." So Stan came back in four hours and the surgeon said, "I got done faster than I expected to. John is down at the local pub." Stan went to the pub and saw John playing darts.
A few weeks later, Stan and John were working again, and John cut his leg off. Stan put the leg in a plastic bag and took it and John back to the surgeon. The surgeon said, "Legs are a little tougher - come back in six hours." Stan returned in six hours and the surgeon said, "I finished early - John's down at the football pitch." Stan went down and there was John, running, tackling, and scoring goals.
A few weeks later, John had a terrible accident and cut his head off. Stan put the head in a plastic bag and took it and the rest of John to the surgeon. The surgeon said, "Gee, heads are really tough. Come back in twelve hours." So Stan returned in twelve hours and the surgeon said, "I'm sorry, John died." Stan said, "I understand - heads are tough." The surgeon said, "Oh, no! The surgery went fine! It’s just that he suffocated in that plastic bag!"