Immune to Pain

A man went to a dentist one day for a regular check up. The dentist decided that one tooth was in such bad condition that it should be extracted. The dentist advised the man of the situation who agreed to the procedure. When the dentist went to give the man an injection the man said "don't worry, I don't need an injection". The dentist went on to explain that the procedure could be very painful however the patient insisted that he would be OK without a needle. The patient went on to explain that he had two experiences in recent times that had made him immune to pain so the dentist went ahead and extracted the tooth. To the dentist's amazement the guy didn't even wince. The dentist, quite astonished remarked " that was amazing, the two recent experiences you say you had that made you immune to pain must have been something special, would you care to tell me about them". The man said "sure, one day I was out hunting and suddenly had an overwhelming urge to evacuate my bowels. I ducked behind a bush and squatted down and my scrotum landed squarely on the trigger of a rabbit trap and CRUNCH!!". The dentist exclaimed "oh my god, that must have been excruciating but what was the second experience". The man replied "when I ran out of chain"