Answer:
Without a bridle, or a saddle, across a thing I ride a-straddle. And those I ride, by help of me, though almost blind, are made to see.
Glittering points that downward thrust. Sparkling spears that never rust.
Runs smoother than any rhyme, loves to fall but cannot climb.
A harvest sown and reaped on the same day In an unplowed field, Which increases without growing, Remains whole though it is eaten Within and without, Is useless and yet The staple of nations.
What goes with a car, comes with a car, is no use to a car but a car cannot move without it?
What scientists might call your pooch.