ELECTROCARDIOGRA M 



11 



varying relationship to each other. It is quite clear from such records 

 that activity or inactivity, partial or complete, in one chamber has no 

 influence on the shape or amplitudes of the electrical currents derived 

 from the other (Fig. 2). Providing that we are dealing with separate 

 masses of heart muscle, the electromotive forces set up in one chamber 

 are not influenced by those set up in the other. The forces developed 

 in the two chambers find full and individual expression ; in explaining 

 such curves we do not balance activity in one chamber against inactivity 

 in the other. 



In regard, therefore, to the illustration (Fig. IE) we are safe in 

 assuming that the activation of strip 1 to 2 at point 1 will yield an 

 electromotive force having a certain direction and amplitude, indepen- 

 dently of what is happening in the strip 2 to 3. How does this arrange- 

 ment of the muscle fibers differ from that illustrated by Figure ID. 



2ZF 



fcstc. 



Fig. 2. Electrocardiograms from a case of complete heart block, and taken 

 by means of Leads I, II and III. 



In one respect only ; in the first illustration there is functional union 

 between the two strips at the point 2. If 1 is stimulated to activity in 

 these two sets of circumstances, will the initial resultant swings of the 

 galvanometer be in opposite directions ; will they indicate relative nega- 

 tivity at Z in one case and at C in the other ? According to the hypothe- 

 sis of distributed potentials this will happen. But in both instances, 

 when 1 becomes active, the strip 2 to 3 is recognized to be in a state 

 of inactivity. The distribution of potentials is the same in both, 

 unless we are to assume that when the two strips are part of one undi- 

 vided piece of muscle, an active change happens in strip 2 to 3, render- 

 ing it relatively more positive to 1. In other words, if we are to accept 

 the hypothesis of distributed potentials, it is essential to assume that, 

 from its initiation, active change produced by stimulation does not 

 confine itself to that end of the muscle which is stimulated. I know of 



