240 



HUMAN PHYSIOLOGY 



s.c 



2nd. Inferior cardiac branch of the vagus leaves the main 



nerve near the re- 

 current laryngeal, 

 and passes to join 

 the superficial car- 

 diac plexus in the 

 heart (Fig. 118,/.(7.). 

 3rd. Sympathetic 

 nerve fibres come 

 from the superior 

 thoracic and in- 

 ferior cervical gan- 

 glia, and also end 

 in the superficial 

 cardiac plexus (Fig. 

 118, 8.). 



Functions of the 

 Cardiac Nerves. 

 A. The Superior 

 Cardiac Branch of 

 the Yagus is an in- 

 going nerve. Sec- 

 tion produces no 

 effect ; stimulation 

 of the lower end 

 causes no effect ; 

 stimulation of the 

 upper end causes 

 slowing of the heart 

 and a marked fall 

 in the pressure 

 of blood in the 

 arteries, and it 

 may cause pain. 



Flo. 118. Connections of the Heart with the Central 

 Nervous System. Au., Auricle; V., Ventricle; 

 V.D.C. y Abdominal Vaso-dilator Centre; C.I.C., 

 Cardiac Inhibitory Centre; C.A.C., Cardio-aug- 

 mentor Centre; S.C., Superior Cardiac Branch of 

 the Vagus; 7.C7., Inferior Cardiac Branch of the 



Vagus with Cell Station in the Heart; S., Cardio- The slowing of the 

 sympathetic Fibres with Cell Station in the Len- heart is a reflex 

 ticular Ganglion; V. D. A b. , Vaso-dilator Fibres 

 to Abdominal Vessels. The continuous lines are 

 outgoing ; the broken lines are ingoing Nerves. 



effect through the 

 inferior cardiac 

 branch ; and the 

 fall of blood pressure, which is the most manifest effect, is 



