INNERVATION OF HEART AND BLOOD-VESSELS 567 



system pass out of the spinal cord in the white 

 rami and terminate in the sympathetic ganglia 

 (for example, the inferior cervical and stellate 

 ganglia of the dog) in contact with sympathetic 

 cells, the neuraxons of which convey the impulse 

 to the heart. 



The cardiac centres are readily affected by 

 afferent impulses from many sources. 



Reflex Inhibition of the Heart; Goltz's Experi- 

 ment. In a very lightly etherized frog, expose 

 the pericardium by cutting away the ctiest wall 

 over the heart. Count the number of beats in 

 periods of twenty seconds. Continue the count 

 while an assistant strikes gentle blows with the 

 handle of a scalpel upon the abdomen at the rate 

 of about 140 per minute. 



The frequency will usually diminish and, in fa- 

 vorable cases, the heart will at length be arrested. 



Cut both vagus nerves and repeat the experi- 

 ment. 



The reflex inhibition of the heart cannot be 

 obtained after section of the vagi. 



It has been shown by Bernstein that the affer- 

 ent nerves in this experiment are abdominal 

 branches of the sympathetic nerve. The stim- 

 ulation of the central end of the abdominal 

 sympathetic in the rabbit also produces reflex 

 inhibition of the heart. 



