690 THE SYMPATHETIC NERVES. 



(6) The filaments connected with the Gasserian ganglion of the fifth nerve pro- 

 ceed sometimes from the carotid plexus, at others from the cavernous. 



(c) The deep branch of the Vidian nerve passes backwards to the carotid plexus, 

 and after leaving the Vidian canal, lies in the cartilaginous substance which closes 

 the foramen lacerum medium. Valentin describes nerves as furnished to the dura 

 mater from the carotid plexus. 



CAVERNOUS PLEXUS. The cavernous plexus, named from its position in 

 the sinus of the same name, is placed below and rather to the inner side of 

 the highest turn of the internal carotid artery. Besides giving branches on 

 the artery, it communicates with the third, the fourth and the ophthalmic 

 of the fifth cranial nerves. 



Blanches. (a) The filament which joins the third nerve comes into connection 

 with it close to the point of division of that nerve. 



(b) The branch to the fourth nerve, which may be derived from either the caver- 

 nous or the carotid plexus, joins the nerve where it lies in the wall of the cavernous 

 sinus. 



(c) The filaments connected with the ophthalmic trunk of the///* nerve are supplied 

 to its inner surface. One of them is continued forwards to the lenticular ganglion, 

 either in connection with or distinct from the nasal nerve. 



2. PHARYNGEAL NERVES AND PLEXUS. 



These nerves arise from the inner part of the ganglion, and are directed 

 obliquely inwards to the side of the pharynx. Opposite the middle con- 

 strictor muscle they unite with branches of the pneumo-gastric and glosso- 

 pharyngeal nerves ; and by their union with those nerves the pliaryngeal 

 plexus is formed. Branches emanating from the plexus are distributed 

 to the muscles and mucous membrane of the pharynx. 



3. UPPER CARDIAC NERVE. 



Each of the cervical ganglia of the sympathetic furnishes a cardiac branch, 

 the three being named respectively the upper, middle and lower cardiac 

 nerves. 



These branches are continued singly, or in connection, to the large 

 prevertebral centre (cardiac plexus) of the thorax. Their size varies con- 

 siderably, and where one branch is smaller than common, another will be 

 found to be increased in size, as if to compensate for the defect. There 

 are some differences in the disposition of the nerves of the right and left 

 sides. 



The upper cardiac nerve (n. cardiacus superficialis) of the right side 

 proceeds from two or more branches of the ganglion, with, in some 

 instances, an offset from the cord connecting the first two ganglia. In its 

 course down the neck the nerve lies behind the carotid sheath, in contact with 

 the longus colli muscle ; and it is placed in front of the lower thyroid artery 

 and the recurrent laryngeal nerve. Entering the thorax, it passes in some 

 cases before, in others behind the subclavian artery, and is directed along the 

 innominate artery to the back part of the arch of the aorta, where it ends in 

 the deep cardiac plexus, a few small filaments continuing also to the front 

 of the great vessel. Some branches distributed to the thyroid body 

 accompany the inferior thyroid artery. 



In its course downwards the cardiac nerve is repeatedly connected with] other 

 branches of the sympathetic, and with the pneumo-gastric nerve. Thus about the 

 middle of the neck it is joined by some filaments from the external laryngeal 



