Under normal conditions one may not expect the left auricle to transmit its movements against the thoracic wall, because it lies almost exclusively at the dorsal aspect of the heart. Also, the degree of the pulsatory amplitude is much too weak to produce visible or palpable pulsatory phenomena. In the presence of disease of the mitral valve the left auricle may dilate exclusively dorsad and occasionally to the right side of the chest (Stoerk1). An anterior roentgenogram will reveal that the left auricle overlaps the right auricle on the right side, resulting in a subdivision of the right cardiac contour. In the presence of mitral regurgitation of a higher degree one notices that these two arches show pulsations in opposite directions. The upper arch corresponds to the left auricle and shows a forceful lateral movement during systole, while the lower arch (right auricle) simultaneously reveals a smaller movement inward.