328 



PHYSIOLOGY 



CHAP. 



Of. 



atropiue or nicotine, stimulation of these nerves no longer causes 



inhibition, but only acceleration of 



rhythm. Heidenhain (1882) and 



G askell ( 1 884) subsequently showed 



that the accelerator fibres are 



derived from the sympathetic, and 



unite with the latter immediately 



after the vagus leaves the cranium 



(Fig. 149). ' 



In 1871 Schmiedeberg, with 

 Ludwig, studied the topography 



B 



l-'ici. 14y. Left. Diagram of frog's cardiac nerves. (After. Foster.) R I", Vagus roots ; .Pi-, cranial 

 wall ; GV, vagus ganglion ; IX, glosso-pharyngeal ; VS, vago-sympathetic : Si; cervical sym- 

 pathetic, which unites with vagus ganglion ; w, sympathetic branch which traverses the 

 cranium and gives oft' libres to the Gasserian ganglion ; Gci, first sympathetic ganglion receiv- 

 ing fibres from tirst spinal nerve; AV, annulus of Vieussens traversed by subclavian artery; 

 Gs, second sympathetic ganglion receiving fibres from second spinal nerve; Gut, third sym- 

 pathetic ganglion, which receives fibres from third spinal nerves, d'lir, via ramus communicans, 

 re. The direction of the arrows indicates direction, tirst ascending, then descending, in which 

 the excitation of the cardiac fibres by the vago-spinal nerves is transmitted to the heart. 



Kir;. loQ.Jtiijht. Diagram of cardiac nerves in dog. (After' Foster.) The upper portion of the figure 

 represents the inhibitory fibres, the lower part the accelerators ; /-I', roots of vagus ; rS, roots 

 of spinal accessory, the internal roots of which, shown by black line, run in the trunk of the 

 vagus, V ; GJ, jugular ganglion ; Gtv, ganglion of vagus trunk ; V, trunk of vagus united with 

 cervical sympathetic to form vago-sympathetic nerve ; Si; cervical sympathetic ; (lei, inferior 

 cervical ganglion; AV, annulus of Vieussens traversed by subclavian artery; GS, stellate or 

 first thoracic ganglion ; we, cardiac nerves, of which the two upper branches come from the 

 accessory or spinal, and the two lower from the first to the fifth thoracic nerves (particularly 

 from second and third, as shown by black lines), the fibres of which ascend by rami com- 

 municantes to the stellate ganglion and from the loop of Vieussens. The direction of the'arrows 

 indicates the direction, first ascending, then descending, in which tin- activity of the cardiac 

 nerves travels to the heart. 



of the cardiac plexus in the dog, and distinguished the inhibitory 

 from the accelerator fibres (Fig. 150). 



