3 i2 TEXT-BOOK OF PHYSIOLOGY. 



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 that the cessation of ventricular action 

 is a secondary effect due to the non-arrival across the conducting apparatus 



FIG. 146. RESULT OF THE STIMULATION OF THE PERIPHERAL END OF THE 

 DIVIDED LEFT VAGUS IN THE RABBIT. (Brodie.) 



of the normal excitation process from the auricle. This is the case un- 

 doubtedly 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 band of His, there is for a 

 time a complete cessation of ventricular activity, but after a variable period of 

 time, fifty seconds or more, the ventricle develops an independent rhythm 

 which gradually increases in frequency, but seldom, if ever, attains that of 



