CARDIAC INHIBITION AND ACCELERATION 



311 



The existence of accelerator fibers has been estabhshed experimen- 

 tally in rabbits by von Bezold^ whose results have been substantiated 

 for warm-blooded animals by M. and E. Cyon,^ and for cold-blooded 

 animals by Schmiedeberg.^ Although it cannot be definitely stated 

 that these fibers arise in or near the cardio-inhibitor center of the 

 medulla, it may justly be assumed that they possess a central origin 



Fig. 162. — Schema Illustra-tinq the Distribution of the Caediao Nerves. 

 MO, medulla oblcngata; CC, cardiac center (inhibitor area ); X, nucleus of vagus 

 nerve, red indicating the course of the inhibitor fibers; SCR, superior cardiac ramus; 

 JCR, inferior cardiac ramus; V, vagus; SL, superior laryngeus; JL, inferior laryngeus; 

 PC, plexus cardiacus, and preganglionic path; SC, spinal cord, the accelerator fibers 

 are indicated in blue, II, III, and IV roots of corresponding thoracic spinal nerves; 

 S, sympathetic ganglion along spinal cord; SG, stellate ganglion; AV, annulus of Vieus- 

 sens; JC, superior cervical ganglion to plexus cardiacus upon arch of aorta. 



and are at least intimately connected with this area. They become 

 clearly recognizable peripherally in the anterior roots of the second, 

 third and fourth thoracic spinal nerves ; in fact, in certain animals also 

 in the lower cervical and first and fifth thoracic nerves. The nerve 

 cells from which they arise are situated in the intermedio-lateral tract 

 of the spinal cord. For this reason, they may be regarded as forming 



* Untersuch. iiber die Innervation des Herzens, ii, 1863. 



* Centralbl. flir die med. Wissensch., 1866. 



^ Ber. der sachs. Gesellsch. der Wissensch., 1870. 



