It is not considered regular to read authorities in the closing argument, unless it be to explain those read upon the opposite side. The party who merely refers to cases in his opening argument, without reading, is understood to acquiesce in such authorities not being read; and unless they are read by the opposite side, he is not strictly entitled to take them up again. A contrary practice must tend to give the excepting party an unequal advantage in the argument, or lead to a double reply.