2. The general requisites of a rejoinder are, 1. It must be triable. 2. It must not be double, nor will several rejoinders be allowed to the same declaration. 3. It must be certain. 4. It must be direct and positive, and not merely by way of recital or argumentative. 5. it must not be repugnant or insensible. 6. It must be conformable to, and not depart from the plea. Co. Litt. 304; 6 Com. Dig. 185 Archb. Civ. Pl. 278; U. S. Dig, Pleading, XIII.