A fluoroscopic study of the position and action of different bits in the horse's mouth

Abstract

Fluoroscopy was used to visualize the position and movements of different types of bits within the horse's oral cavity. The jointed eggbutt snaffle normally lay between the tongue and palate with the joint hanging down toward the incisor teeth. By arching and elevating the tongue the horse was able to raise the mouthpiece between the cheekteeth. The jointed mouthpiece was suspended in a more horizontal position when keepers were used with a cheek snaffle to fix the position of the bit rings relative to the cheekpieces of the bridle. In addition, the mobility of the bit within the oral cavity was reduced by using keepers. Similarly less intra-oral movement was observed in bits with an unjointed mouthpiece. The Dr. Bristol bit, which has two joints connected by an angled plate, could be attached to the bridle in two ways so that the plate lay either parallel to the tongue and palate or perpendicular to them. This would be expected to have a marked effect on the severity of action of the bit. The high tongue port of the Hannoverian pelham pressed against the palate when the reins were used, causing considerable discomfort.