BBC Four TV took us on a different voyage with Guts: The Strange And Mysterious World Of The Human Stomach.
It's not just digestion going on down there. There's a second brain at work. The nine metres or so of the alimentary canal is studded with hundreds of millions of neurons.
As the BBC put it: "The little brain in our innards, in connection with the big one in our skulls, partly determines our mental state." More scientifically, the enteric nervous system does not just collect information and pass it upstairs. It integrates the data and acts on it.
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