Hospitals formerly employed arrow root in barium meals given prior to X-raying the gastro-intestinal system.  When mixed with hot water, the root starch of this plant becomes gelatinous and serves as an effective demulcent to soothe irritated mucous membranes.  Used in much the same way as slippery elm.  It helps to relieve acidity, indigestion, and colic, and it exerts a mildly laxative action on the large bowel.