It was a few years ago.
I was walking home, the same 2.3 mile walk I did everyday. I usually just zone out for minutes on end and eventually arrive at my destination. Near the end of my walk, I happened to glance down and there a big piece of Birch tree bark, round and fairly thin - about the size of my forearm. It was just so . . . there. Like right there! So I picked it up and started eating it, and I continued walking, munching as I went. About a half block later, I realized what I was doing, but rather than stop, I started marveling at my absent-mindedness, whilst continuing to chew. My mouth just kept filling up with more and more bark, because I couldn't chew it to the point at which it was swallowable. I was nearly home by the time my mind consciously registered what I was doing and I started laughing, and chips of wood sprayed out of my mouth. Then I took another bite and started absent-mindedly chewing again.
God, that walk was so mind-numbingly LONG.
