Dear WW: As I said, it is so routine it does not cause comment. I just had a thought. I said it was the brain center that caused it. I now think it is result of spinal centers being released from central control. I wonder if doc_comfort would think that a possible explanation.

With regard to spinal centers being actve after being released from control of brain, remember how a chicken's legs thrash for severa seconds after its head is chopped off.