CARDIAC INHIBITION AND ACCELERATION 



321 



of the other nerve alone suffices to give a maximal effect. Either the 

 right or the left nerve may be the more powerful. It need scarcely be 

 mentioned that these inhibitor reactions may also be incited by the 

 stimulation of the distal end of the divided vagus, the electrodes being 

 applied either to the right or to the left nerve. In some animals 

 (cat) it is also possible to produce a moderate inhibition by stimulating 

 the central stump of either vagus, provided, of course, that the opposite 

 nerve has been left intact. This effect is easily explained, because 



FIG. 169. To SHOW THE EFFECT OF SECTION OF THE Two VAGI IN THE DOG UPON THE 



RATE OF HEART BEAT AND THE BLOOD-PBESSUKE. 



1, Marks the section of the vagus on the right side; 2, section of the second vagus. 

 The numerals on the vertical mark the blood-pressures; the numerals on the blood- 

 pressure record give the rate of the heart beats. (Dawson.) 



these nerves also conduct impulses from the heart to the center, where 

 they affect the cardiomotor mechanism in a reflex way. In most 

 cases, these afferent stimuli give rise to an inhibition, but it also 

 happens at times that they incite a slight augmentation. This result 

 is usually observed in dogs. 



If the blood pressure is registered during these stimulations of 

 the vagus nerve, it can readily be established that the inhibition of the 

 heart is associated with a fall in the arterial and a rise in the venous 

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