28 



The next three nerves (glossopharyngeal, vagus, and hypoglossal) are best 

 examined in a dissection from below. See page 8. When the mylohyoid is 

 removed, and the oesophagus distended, the hypoglossal will be seen appear- 

 ing immediately in front of the brachial plexus, and then arching forwards 

 in the substance of the genio-hyoid muscle to end in the muscles of the 

 tongue. About two lines in front of the hypoglossal is the glossopharyngeal. 

 It escapes from the skuU behind the auditory capsule, and runs forward at 

 first nearly parallel to the hypoglossal, but it soon crosses the hypoglossal as 

 it passes to the base of the tongue. Eunning obliquely across the space 

 between these two nerves at a deeper level is the vagus, while crossing the 

 space it gives off the laryngeal nerve, and, after passing under the hypo- 

 glossal, it breaks up into branches for the heart, lungs, and stomach. 



14. The glossopharyngeal nerve (IX.) leaves the skuL. along with the vagus 

 immediately behind the auditory capsule, and divides into — 



a. An anterior branch which bends round the auditory capsule to join the 



facial nerve in front of the columella. 

 6. A posterior branch, which, after passing under tEe petrohyoid muscle 



and the hypoglossal nerve, takes a sinuous course between the 



geniohyoid and the hyoglossus towards the base of the tongue, 



which it enters. 



15. The pneumogastric or vagus (X.), which, immediately after passing through 

 the skull, leaves the IX. nerve and expands to form a ganglion. After giving 

 off branches to the dorsal muscles, it reaches the walls of the pharynx, and 

 runs obliquely downwards and backwards to break up into the following 

 branches — 



a. The laryngeal branch, which, passing between the glossopharyngeal and 

 hypoglossal nerves and over the pulmo-cutaneous artery, reaches and 

 supplies the larynx. 



h. The cardiac, which reaches the inter-auricular septum by passing dorsal 

 to the pulmonary artery. 



c. The pulmonary, which extends along the pulmonary artery to the 



lung. 



d. The gastric, which extends downwards along the side of the oeso- 



phagus to reach the stomach. 

 Indicate in ventral and lateral views of the head, the distribution of the 

 v., VII., IX., and X. nerves. 



