ROOTS, TRUNK, BRANCHES OF VAGUS NERVE 33 



technique (Ranson '11, '12); some was fixed in Mailer's fluid and 

 stained by the Weigert method; and some was fixed and stained 

 in 1 per cent osmic acid. All of the material was imbedded 

 in paraffin and cut into sections varying from 5 to 15 microns in 

 thickness. 



THE GROSS ANATOMY OF THE VAGUS IN THE DOG 



The vagus nerve in the dog arises by means of a large number 

 of small rootlets from the dorso-lateral sulcus of the medulla ob- 

 longata, in series with the roots of the glossopharyngeal and ac- 

 cessory nefves. In figure 1, a, the rootlets of the vagus proper 

 are seen running into the jugular ganglion; and, joining the vagus 

 at the side of the ganglion, is seen the spinal root of the accessory 

 nerve c. Scattered fine rootlets, h, which have come from the 

 medulla, are seen joining the spinal root. These two nerves 

 (vagus and accessory) are fused into a single trunk at the level 

 of the jugular ganglion. Below the jugular ganglion the pharyn- 

 geal branch of the vagus and the external branch of the accessory 

 are given off from the common trunk. The superior laryngeal 

 nerve leaves the vagus at the level of the nodose ganglion. Some- 

 what below the level of this ganglion the sympathetic trunk joins 

 the vagus and runs downward in the same connective tissue 

 sheath with it. Communicating branches from the sympathetic 

 join the pharyngeal and superior laryngeal branches of the vagus. 

 Just above the subclavian artery there is developed in close con- 

 nection with the vagus the inferior cervical ganglion of the sym- 

 pathetic. From this the ansa subclavia runs to the ganglion 

 stellatum. From the right vagus, immediately below the infe- 

 rior cervical sympathetic ganglion, there is given off the recur- 

 rent nerve. This receives a branch from the inferior cervical 

 sympathetic ganglion and from it runs a large branch to 

 the posterior cardiac plexus. In the thorax the vagus gives off 

 branches to the root of the lung and is then continued into the 

 esophageal plexus. Here the right vagus, joined by a branch 

 from the left, runs on the right side and posterior aspect of the 

 esophagus to reach the posterior aspect of the stomach. It gives 

 off many fine branches to the esophagus. 



THE JOURNAL OF COMPARATIVE NEUROLOGY, VOL. 24, NO. 1 



