970 



PHYSIOLOGY 



In the dog (Fig. 446) the sympathetic fibres leave the spinal cord 

 by the anterior roots of the second and third dorsal nerves, run in the 

 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, 



>> Juq. Ganql. Vagus 



Vago-symparheHc 



Subclav. art 



Splanchn. n. 

 Intesl-. arf 



FIG. 445. 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.) 



similar to the 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 synapses 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 men- 

 tioned. 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 Remak's ganglion, and probably all the other intrinsic cardiac 

 ganglia described above, whence non-medullated fibres carry their impulses 

 to the heart- muscle. 



