Electrocardiography is that phase of cardiography which deals with the direction, the time relations and the magnitude of the "action currents" of the heart.1 It does not register the strength of the contraction of the heart muscle, but it is merely the expression of the electrochemical processes concerned with the contraction of the heart muscle.
Electrocardiography in children is a large and fertile field for clinical research. In spite of the many and noteworthy contributions that have been made to the diseases of circulation in general with the aid of the electrocardiograph, no attempt has as yet been made in this country at a systematized and comprehensive investigation of this subject in children. In the electrocardiograph there are great possibilities for a study of physiologic peculiarities of the normal heart of the child. Through it we can obtain a clearer conception of the peculiarities of the heart mechanism during