Answer:
A man calls his dog from the opposite side of the river. The dog crosses the river without getting wet, and without using a bridge or boat. How?
It is the great nemesis of the lactose intolerant.
Runs smoother than any rhyme, loves to fall but cannot climb.
Halo of water, tongue of wood. Skin of stone, long I've stood. My fingers short reach to the sky. Inside my heart men live and die.
Always old, sometimes new. Never sad, sometimes blue. Never empty, sometimes full. Never pushes, always pulls.
What do you purposefully put lots of in and on your body, but run away from when you encounter it outside?