ON THK VAGUS NERVES OF THE EDENTATA S9 



6. On the Vagus and Sympathetic Nerves of the Edentata. 

 By Charles F. Sonntac4, M.D., F.Z.S., Anatomist to 

 the Society. 



[Received December 28, 1921: Read February 21, 1922.] 



(Text-figures 1-5.) 



In a former paper (2) I showed that the cervical parts of the 

 vagus and sympathetic nei'ves are fused to form vago-sympathetic 

 cords (type 1), or are simply linked together by communicating 

 branches (type 2). And these forms are distributed in the 

 Edentata as follows : — 



Type 1 : — Bradypus tridactylus. 



Type 2 : — Euphractus villosits and Tatusia novemcincta. 



In Tamandua tetradactyla both forms are present in the neck 

 of the same animal, the first occurring on the right side and the 

 second on the left. 



In all species the course of the vagi from the foramen lacernm 

 posticum to the point where they reach the sides of the oesophagus 

 in the posterior part of the thorax is similar to that in the 

 Marsupialia (1,2). The relations differ, however, for the branches 

 of the aortic arch are more frequently similar to those in Hoino. 

 Consequently the relations resemble those described in Anthro- 

 potomy. The branches also differ in many respects from those 

 in the Marsupialia. 



Tamandua tetradactyla (text- figs. 1 and 2). 



The vagus nerves communicate with the glosso-pharyngeal, 

 spinal accessory and hypoglossal nerves by very fine filaments, bvit 

 no branches run to the sympathetic in the anterior part of the 

 neck. And neither vagus has any trace of the ganglion nodosum 

 in the neck, but they are flatter and wider in the foramen lacerum 

 posticum. The usual branches of distribution are given off, but 

 these have a longer course, and are more easily studied than in 

 most Mammals. They foi-m thick bands, with the spinal accessory 

 nerves in the lacerate foramina. 



The pharyngeal nerve (a) is the largest cei-vical branch. It 

 runs along the side of the pharynx and oesophagus and supplies 

 both. It forms a plexus with branches of the glosso-pharyngeal 

 nerve (ix), but no branches of the sympathetic are seen running 

 into it. On the right side a branch (l.h.v) of the hypoglossal 

 nerve (xii) communicates with the pharyngeal branch ; and this 

 nerve may correspond to what is termed the " lingual branch of 

 the vagus" in human anatomy (3). 



The superior laryngeal nerve (6) divides into three branches. 

 One gains the interior of the larynx through the thyro-hyoid 



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