THE PERIPHERAL NERVOUS SYSTEM. 405 



the superior cervical gang^lioti the sympathetic trunk passes 

 caudad usually closely bound up with the vaj^us (<-/'), so that 

 the two can scarcely be distinguished. They lie (/) at the side 

 of the trachea ( c ), close against the lateral surface of the carotid 

 artery. A few centimeters before reaching the first rib the two 

 separate (Fig. 157, page 381); the sympathetic (r) is here the 

 smaller and more dorsal of the two. Just craniad of the first 

 rib the sympathetic usually forms a small swelling, the middle 

 cervical ganglion (Fig. 157, d), beyond which it divides into 

 two portions. The larger dorsal division passes dorsocaudad 

 and joins a large ganglion, the inferior cervical (r), which 

 lies at the head of the first rib, on the lateral surface of the 

 longus colli muscle. The ventral branch {g') passes caudad, 

 turns laterad about the medial and caudal surface of the 

 subclavian artery, and likewise reaches the inferior cervical 

 ganglion. 



In some cases the middle cervical ganglion (c/) is lacking. 



Branches of the Sympathetic in the Cervical Region. — 

 From the cranial end of the superior cervical ganglion several 

 nerves pass craniad. Some of these become connected im- 

 mediately with the cranial nerves emerging from the jugular 

 foramen, forming a plexus in this region. Others pass with 

 the internal carotid artery craniad, forming a plexus about that 

 artery; from the plexus twigs arise which pass to the fifth and 

 sixth cranial nerves; doubtless also to the seventh and eighth. 

 A specially large branch, the deep petrosal nerve (see page 

 373), passes from the superior cervical ganglion along with the 

 internal carotid artery to the pterygoid canal, thence through 

 this to the sphenopalatine ganglion. Before separating from 

 the vagus the sympathetic gives off one or two cardiac nerves 

 (Fig. I 57, i). These are closely bound up with the vagus (^), so 

 that they appear usually to have origin from the vagus at about 

 the level of the first rib. These pass with the vagus to the 

 heart and take part in the formation of the cardiac plexus (/•). 



At the middle cervical ganglion (c/) usually a communicat- 

 ing branch is given to the vagus. The branches of the inferior 

 cervical ganglion {c) fall in the thoracic region, and are 

 described in that connection. 



