The purpose in telling the story of old Hank Bunker, who was buried between two barn doors, after Jim‘s bout with snakebite is to provide?

The story of Hank Bunker provides a sense of comic relief.

".... I’ve always reckoned that looking at the new moon over your left shoulder is one of the carelessest and foolishest things a body can do. Old Hank Bunker done it once, and bragged about it; and in less than two years he got drunk and fell off of the shot-tower, and spread himself out so that he was just a kind of a layer, as you may say; and they slid him edgeways between two barn doors for a coffin, and buried him so, so they say, but I didn’t see it."