THE NERVOUS REGULATION OF THE HEART 1089 



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 

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



G.J. 



G.li.V-- 



r.Vg. 



r.Sp.Ac. 



D.5. 



FIG. 448. Diagram of cardiac inhibitory and accelerator fibres in 



the dog. (From FOSTER.) 



r.Vg, roots of the vagus ; r.Sp.Ac, roots of the spinal accessory ; GJ, 

 ganglion jugulare ; G.h.V, ganglion trunci vagi ; Vg, trunk of vagus nerve ; 

 C.Sy. cervical sympathetic ; GO, inferior cervical ganglion ; AV, annulus of 

 Vieussens ; A.sb, subclavian artery ; nc, cardiac nerves ; G.St, ganglion 

 stellatum ; D2, D3, D4, D5, second, third, fourth, and fifth dorsal spinal 

 roots ; G.Th, ganglia of the thoracic chain. 



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 while the arterial blood pressure is being recorded by 



69 



