THE NEKVOUS REGULATION OF THE HEART 1013 



white rami communicantes to the stellate ganglion, and thence by the 

 annulus of Vieussens to the inferior cervical ganglion. Cardiac branches 

 convey the sympathetic fibres to the heart and are given off from the 

 stellate ganglion, the inferior cervical ganglion, and from the trunk of 

 the vagus. 



By the nicotine method it is possible to trace out the cell connections of 

 these fibres. As they leave the cord they are medullated nerve fibres, similar to the 



>> Jucj. Ganql. Vagus 



Vago -sympathetic 



Subclav. arh 

 N. 



r Aorfa 



Splanchtv n. 

 Infest art- 



N.VI. 



N.VII. 

 N.VIII. 



FIG. 454. Sympathetic chain of frog (right side) to show connection with vagus 

 nerve. The sympathetic ganglia with their branches are black. Of the 

 peripheral branches only the splanchnic nerve is represented. (Modified 

 from ECKER.) 



other fibres making up the visceral outflow throughout the dorsal region ; the white 

 fibres pass along the ramus communicans to the stellate ganglion, where they end, 

 forming sT/ra^ses with the cells of the ganglion. Here fresh relays of fibres, which 

 are non -medullated, start and carry the impulses to the heart along the various cardiac 

 nerves just mentioned. In the heart these fibres are distributed to the muscle fibres 

 without the intervention of any other ganglion cells. On the other hand the fibres, 

 which leave the vagus to pass to the heart, make connection with the cells of Keniak's 

 ganglion, and probably with all the other intrinsic cardiac ganglia described above, 

 whence non -medullated fibres carry their impulses to the heart muscle. 



ACTION OF THE VAGUS 



The action of the vagus fibres on the heart is almost identical in frog and 

 mammal. If in the dog the peripheral end of the cut vagus be stimulated, 



