It is known that the electrocardiogram undergoes certain changes when the position of the heart in the chest is altered. Einthoven1 demonstrated that this change took place when the body was rotated from side to side. He showed also that breathing affected the form of the electrocardiogram as it changed the position of the heart, the more transverse position at the end of expiration being associated with more of a left axis, or a tendency in that direction, while at the end of inspiration the axis shifted in the opposite direction. Cohn2 demonstrated that there is a rather definite relation between the anatomic angle of the heart as measured on the roentgenogram and the electrical angle as derived from the electrocardiogram. In other words, as the position of the heart becomes more transverse, the electrocardiogram shows a gradually increasing left axis deviation, and as the position becomes more transverse, the