670 



THE NERVUS ACCELERANS AND THE CARDIAC PLEXUS. 



nerve. Some of these fibres, issuing from the spinal cord, pass through he nrsnhoraic 

 sympathetic ganglion and the ring of Vieussens, to jam the cardiac plexus (hgs. 469, 

 470 rrhese fibres, proceeding from the spinal cord, frequently accompany the 

 nerve running along the vertebral artery], and they constitute the Nervus accelerant 

 cordis rFi* 470 shows the accelerator fibres passing through the ganglion stellatum 

 of the cat to join the cardiac plexus.] If the vagi of an animal be divided, stimu- 

 lation of the medulla oblongata, of the lower end of the divided cervical spinal cord, 



Fig. 469. Fig. 470. 



Fig. 469. Scheme of the course of the accelerans fibres. P, pons; MO, medulla oblongata ; 

 C, apinal cord ; V, inhibitory centre for heart ; A, accelerans centre ; Vag., vagus ; SL, 

 superior, IL, inferior laryngeal ; SC, superior, IC, inferior cardiac ; H, heart; C, cerebral 

 impulse; S, cervical sympathetic ; a, a, accelerans fibres. Fig 470. Cardiac plexus, and 

 ganglion stellatum of the cat. R, right, L, left x 1 ; 1, vagus ; 2' cervical sympathetic, 

 and in the annulus of Vieussens; 2, communicating branches from the middle cervical gan- 

 glion and the ganglion stellatum ; 2", thoracic sympathetic : 3, recurrent laryngeal ; 4, 

 depressor nerve ; 5, middle cervical ganglion ; 5', communication between 5 and the vagus; 

 6, ganglion stellatum (1st thoracic ganglion) ; 7, communicating branches with the vagus ; 

 8, nervus accelerans ; 8, 8', 8", roots of accelerans ; 9, branch of the ganglion stellatum. 



even of the lower cervical ganglion, or of the upper dorsal ganglion of the 

 sympathetic (Gang, stellatum), causes acceleration of the heart-beats in the dog and 

 rabbit, without the blood-pressure undergoing any change (CI. Bernard, v. Bezold, 

 Cyon). 



On stimulating the medulla oblongata or the cervical portion of the spinal cord, the vaso- 

 motor nerves are, of course, simultaneously excited. The consequence is that the blood-vessels, 

 supplied by vaso-motor nerves from the spot which is stimulated, contract, and the blood- 

 pressure is greatly increased. Again, a simple increase of the blood-pressure accelerates the 

 action of the heart ; this experiment does not prove directly the existence of accelerating fibres 

 lying in the upper part of the spinal cord. If, however, the splanchnic nerves be divided 

 beforehand (when, as they supply the largest vaso-motor area in the body, the result of their 

 division is to cause a great fall of the blood-pressure), then on stimulating the above-named 



