Reversal of the Cardiac Mechanism. 41 



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Reversal of the cardiac mechanism. An additional note. 



By Horatio B. Williams and Henry James. 



[From the Physiological Laboratory of Columbia University, 



New York.] 



Since making our previous report on this subject, electro- 

 cardiograms have been obtained from the same patient in which 

 occasionally the small downward deflection between R and T 

 fails. The form of the ventricular electrogram in these instances 

 is precisely similar to the others with the sole exception of the 

 absence of the small downward deflection. This we regard as 

 confirmatory evidence of the correctness of the view that the 

 downward deflection is caused by the action of the auricles and 

 that the usual curve is not simply an unusual ventricular complex. 

 In the occasional instances cited conduction seems to have failed. 



When this case first came under observation it seemed desirable 

 to attempt to reproduce the condition experimentally. We have 

 performed up to the present time seven experiments with one 

 positive result. Rothberger and Winterberg have published 

 curves showing transient reversal resulting from simultaneous 

 depression of the sinus-region of the right auricle with cold and 

 stimulation of the left ganglion stellatum. The apparent perma- 

 nence of the condition in our patient leads us to think rather of an 

 anatomical lesion than of nervous influences as the cause of the 

 condition. Our experiments have consisted in depression (with 

 anode) crushing, and excision of the region of the sinus node. In 

 some instances nearly the entire anterior wall of the right auricle 

 including a large part of the walls of the venae cavae where they 

 fuse with the auricle, have been excised. 



Slowing of the heart beat was the usual result and the auricles 

 and ventricles generally beat nearly or quite simultaneously. In 

 the single positive experiment auricular fibrillation resulted from 

 the application of a clamp to the upper part of the sinus region 

 where the greater bulk of the node is usually found. This per- 

 sisted for twenty minutes and stopped immediately on application 

 of a second clamp immediately below the first. The auricles 



