The Galloping Past Dodge.
Some horses roar loudly when going fast in harness, but are instantly quiet when action ceases. To prevent the detection of this unsoundness the seller, unless prevented from doing so by an experienced buyer, gallops the horse past the latter and, by tugging upon the lines, makes it appear that the animal is trying to run away or is difficult to control. The team is pulled up some distance away and by the time the buyer gets there the horse has resumed normal breathing.
The better way to test the horse’s wind is to lock the rear wheels of a wagon by thrusting a strong stick between the spokes from one wheel to the other; then make the horses pull the wagon at a run and be at their heads the moment they stop. Such horses may not be true roarers but mechanical chokers with thick, bull necks or enlarged throat glands. These are practically sound and only roar when pulling a heavy load up hill or on getting the chin down close to the chest.