THE PERIPHERAL NERVOUS SYSTEM. 405 
the superior cervical ganglion the sympathetic trunk passes 
caudad usually closely bound up with the vagus (a@’), so that 
the two can scarcely be distinguished. They lie (z) at the side 
of the trachea (6), 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 (c) 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, @), beyond which it divides into 
two portions. The larger dorsal division passes dorsocaudad 
and joins a large ganglion, the inferior cervical (ec), 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 (@) 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 
thé vagus the sympathetic gives off one or two cardiac nerves 
(Fig. 157, 2). These are closely bound up with the vagus (4), 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 (4). 
At the middle cervical ganglion (d@) usually a communicat- 
ing branch is given to the vagus. The branches of the inferior 
cervical ganglion (e) fall in the thoracic region, and are 
described in that connection. 
