A man is holding a pocket knife while sitting on some rocks in the wilderness.  Then he takes a small stone from the flowing river and smashes it on another stone.  He starts to crush the small stone to smaller pieces.  He grind it hard to make the pieces smaller.  Then he takes a piece of bark and rubs the powered stone pieces onto it.  The stone particles stick to the wet piece of wood.  He then takes the knife and sharpens it against the wood piece.  He then notices a little black and green poisonous frog sitting next to him.  The frog then escapes and jumps away.  He explains how the frog secretes a poisonous fluid that can be extremely harmful.