SYMPATHETIC NERVfiS OF THE EDENTATA. l03 



any ascending aortic branch. In addition to the communicating 

 nerves to the intercostals, and filaments to the oesophagus, aorta 

 and mediastinum, splanchnic nerves are given ofF. 



The Solar or Cmliac Ple.vus (text-fig. 2) consists of several 

 ganglia and communicating bundles of fibres, and is divisible 

 into upper and lower parts. It is connected to the sympathetic 

 cords by splanchnic nerves (h) ; these are three in number, but 

 the lowest is really a bundle of fibres. It lies betweeii the layers 

 of the mesentery, along the course of the cceliac axis, and is not 

 set across the vertebral column. The following are the branches 

 of distribution : — 



A. From the upper part of the plexus. 



1. Hepatic plexus (i) which communicates with the gastric 

 branches of the right vagus (/) by nerves meeting in a small 

 ganglion. 



2. Splenic plexus (k) communicating with the right vagus and 

 supplying spleen and pancreas. 



3. Phrenic plexus (J) communicating with the phrenic nerve in 

 the diaphragm. 



B. From the lower part of the plexus. 



1. Bight renal plexus (m). 



2. Communicating branches to the splanchnic nerves and aortic 

 plexus (n). 



The Aortic Plexus (p) accompanies the aorta and its branches. 

 It communicates with the splanchnic nerves, sympathetic cords 

 (RS and LS), and their common ganglion. And it gives oflf the 

 left renal plexus (o). 



The abdominal parts of the sympathetic have few ganglia. They 

 gradually diminish in size and meet in a common ganglion in 

 front of the sacrum. From the latter nerve plexuses run to the 

 pelvic viscera. 



Euphractus villosus (text-figs. 3 and 4). 



The vagus and sympathetic nerves differ in many ways from 

 those in Tamandua. 



The Vagus Nerves : — The ganglion nodosum (G.JST) is present 

 on both sides. And the branches of communication to the other 

 cranial nerves and the superior cervical ganglion of the sympa- 

 thetic are well marked. In the middle of the neck a thick 

 communicating branch connects the right vagus and sympathetic. 



The pharyngeal branch (a) arises above the ganglion nodosum, 

 and no nerve connects it to the hypoglossal nerve. 



The superior laryngeal nerve (h) is a thick branch arising from 

 the centre of the ganglion nodosum. It divides into a thick 

 internal laryngeal nerve {i.l.n) and a thin external laryngeal 

 nerve (e.l.n) which receives a loop from the superior cervical 



