Answer:
Deep, deep, do they go. Spreading out as they go. Never needing any air. They are sometimes as fine as hair.
The more you take away from me the bigger I shall get.
I am an English word that is as long as I am valued.
Used left or right I get to travel over cobblestone or gravel. Used up I vie for sweet success used down I cause men great duress.
I have a head, tail, but no arms and legs. What am I?
A little house full of meat, no door to go in and eat.