A Farmer walks into the local bar and sits down at the bar.

The Farmer mumbles, "Some things I just can't explain." The bartender, who knows the Farmer as Jim, asks, "What do you mean Jim?".
"Well, you know my old cow Betsy? I was milking her this morning and out of the blue she knocks the pail of milk over with her right back leg. So I picked up a piece of rope laying nearby and cut me off a piece. I tied her leg to the post nearby, but some things I just can't explain," Jim said.
"Jim, What do you mean by that," the Bartender asks.
"Well, I commenced to milking her again and when the pail got half full she kick it over with her left back leg. So I took the left over piece of rope and tied her other leg to another post, but some things I just can't explain," Jim added.
"Jim, tell me what it is you can't explain and I'll see if I can help," the Bartender said.
"Well, after that I went back to milking her and again I got the pail half full and I'll be darned if she didn't knock the pail over with her tail. Since I didn't have any more rope left I took off my belt and tied one end to her tail. Then I stood up on my stool and reached up to hook the buckle on a nail just above. About that time my pants fell to my ankles and my wife walks into the barn. That's what I can't explain."