Influence of Vagus Nerves on Auricles. 



85 



latory movements in the various fibers could be seen. When the 

 right vagus was stimulated with a faradic current of moderate 

 strength, the coarser movements ceased and the typical fine 

 fibrillations persisted, and when the stimulation was removed the 

 coarser movements could be seen definitely, gradually returning 

 and being coexistent with the fine fibrillation. This effect pro- 

 duced a change in the electrocardiogram and the undulations 

 representing auricular activity became more rapid, blurred and 

 often almost disappeared. This characteristic change in the 

 electrocardiograms occurred in 89.5 per cent, of the experiments. 



When the left vagus was stimulated the coarser movements of 

 the auricles were not disturbed, but appeared sometimes perhaps 

 even more distinctly than before. It was difficult to determine 

 with certainty whether the fibrillatory movements ceased or were 

 influenced. There was a definite difference in the electrocardio- 

 grams when the right and left vagi were stimulated during the 

 abnormal auricular activity in 70.5 per cent, of the experiments, 

 the larger waves of auricular activity being much less or not at 

 all disturbed by stimulation of the left nerve. 



Thus the difference between the action of the two vagi in the 

 dog, pointed out by Cohn, 1 is further extended. 



Cutting the vagi after the establishment of the abnormal 

 auricular activity had little or no effect upon it, but the ventricular 

 rate was sometimes much increased. Vagus stimulation increased 

 the susceptibility of the auricles to faradization, and in four experi- 

 ments the abnormal auricular activity could be made to continue 

 after the faradization was stopped only by stimulating the vagi 

 synchronously with or for a few seconds after faradization. In 

 two experiments an auricular activity identical with that following 

 faradization was set up by right vagus stimulation alone. 



The normal sequential beat is also often restored by vagus 

 stimulation. It replaces the abnormal auricular activity not 

 during, but a few seconds after the termination of vagus stimula- 

 tion. Left vagus stimulation seems somewhat more effectual in 

 producing this effect than right vagus stimulation. 



1 Cohn, Jour. Exper. Med., 1912, XVI, 732. 



