in Anatomy, the same with Kidneys. See Anatomy Index.

REINS of a Bridle, are two long slips of leather, fastened on each side of a curb or snaffle, which the rider holds in his hand, to keep the horse in subjection.

There is also what is called false reins; which is a path of leather, passed sometimes through the arch of the banquet, to bend the horse's neck.