.SYMPATllliTIC NJiHVES UF T]1E EDENTATA. 105 



border of the fiovtic arch. Fibres radiate fi'om it over the arch 

 and its branches, and constitute the superficial cardiac plexus. A 

 branch of the left rectcrrent nerve (e) ends in the plexus, but the 

 recurrent and lower left cardiac nerves do not communicate as in 

 Tamandaa. Tiie right vagus gives two branches to the deep 

 cardiac plexus, but none to the superficial one. 



The right recurrent nerve [d) has the usual origin, course, and 

 relations. It communicates with the sympathetic, and a fine 

 branch crossing the front of the trachea., connects it to the left 

 nerve. 



The pulmonary nerves (g) are given off as the vagi reach and 

 pass behind the roots of the lungs. And they are connected by 

 fine nerves to the deep cardiac plexus. 



The posterior thoracic parts of the vagi difier from those in 

 Tamandaa. The right vagus runs along the ventral aspect in 

 the oesophagus. The left nerve runs along the dorsal surface of 

 the oesophagus and communicates with the right one. It gives 

 ascending, transverse, and descending branches to the oesophagus 

 and aortic plexus. In the abdomen the right vagus breaks up 

 into a number of branches which run along the ventral surface 

 of the stomach close to the lesser cui-vature. The left vagus 

 gives several twigs to the coeliac plexus and its oflshoots, and 

 ends in the dorsal wall of the stomach. 



The Cervical Sympathetic : — The superior cei'vical ganglion 

 (S.C.G) is large and round. It communicates with the cranial 

 nerves in its vicinity, and sends a loop to the external laryngeal 

 nerve {e.l.n). Twigs of communication run to the ganglia 

 connected to the laryngeal nerve. The internal carotid nerve 

 (i.c.n) is given off as usual to accompany the internal carotid 

 artery into the skull. The m.iddle cervical ganglia are absent, 

 and the inferior cervical ganglia (I.O.G) are smaller and narrower 

 than those in Tamandaa. And the cardiac nerves are similar to 

 those in the latter. 



The Cardiac Plexuses (S.O.P an<l D.O.P) difier from those in 

 Tamandaa. The superficial one is formed entirely by the left 

 vagus and sympathetic, and has a well-marked ganglion of 

 Wrisberg (G.W). The deep plexus is' composed of branches of 

 the right vagus and sympathetic, and its solitary ganglion is 

 applied to the wall of the right auricular appendix. The two 

 plexuses are united by fine communicating branches. 



The thoracic cords contain few ganglia as in Tamandua. 

 They increase in thickness from before backwards, and the 

 splanchnic nerves {h) are given ofi" from an enlargement. There 

 is no branch comparable to the ascending aortic branch in 

 Tamandua. The abdominal part has few ganglia, and its rami 

 communicantes to the lumbar nerves {c.l.p) are well marked. 



The Coeliac Plexus (text-fig. 4) consists of right and left halves 

 connected by bundles of fibres, and united to the sympathetic 

 cords by the splanchnic nerves (A). It lies between the layers 

 of the common mesentery, along the covuse of the coeliac axis. 



