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.
What do you call a three humped camel?
Break me and I am better immediately set and harder to be broken again.
Use me if you really want to see inside someone
My second is performed by my first. A thief by the marks of my whole might be caught. What am I?
Sometimes I am white, sometimes I am dark. Most people love me. What am I?