322 TEXT-BOOK OF PHYSIOLOGY 



strong current was followed by a diminution in both the rate and force of the 

 contraction of both auricles and ventricles, though the effect was most 

 marked in the auricles. From this and similar facts it has come to be the 

 general belief that the inhibitor nerve impulses exert their influence mainly} 

 if not exclusively, on the auricle, and especially on the sino-auricular node, 

 and that the cessation of ventricular action is a secondary effect due to the 

 non-arrival across the conducting apparatus of the normal excitation process 



FIG. 144. RESULT OF THE STIMULATION OF THE PERIPHERAL END OF THE DIVIDED LEFT 

 VAGUS IN THE RABBIT. (Brodie.) 



from the auricle. This is the case undoubtedly in the cold-blooded animals, 

 and the experiments of Erlanger on the heart of the dog indicate that the 

 same holds true for the mammals. This investigator has found that when 

 the auriculo-ventricular tissues are suddenly clamped, including presumably 

 the muscle bundle of His, there is for a time a complete cessation of ven- 

 tricular activity, but after a variable period of time, fifty seconds or more, 

 the ventricle develops an independent rhythm which gradually increases in 





