CERVICAL GANGLIA. 595 



offsets which pass to the otic ganglion and to the intumescentia gangliformis of 

 the facial nerve. 



The MIDDLE CERVICAL GANGLION (thyroid ganglion) is the smallest of the three 

 cervical ganglia, and is occasionally altogether wanting. It is placed opposite the 

 fifth cervical vertebra, usually upon, or close to, the inferior thyroid artery; hence 

 the name " thyroid ganglion," assigned to it by Haller. 



Its superior branches ascend to communicate with the superior cervical 

 ganglion. 



Its inferior branches descend to communicate with the inferior cervical 

 ganglion. 



Its external branches pass outwards to join the fifth and sixth spinal nerve?. 

 These branches are not constantly found. 



Its internal branches are the thyroid and the middle cardiac nerve. 



The thyroid branches are small filaments, which accompany the inferior thyroid 

 artery to the thyroid gland ; they communicate, on the artery, with the superior 

 cardiac nerve, and, in the gland, with branches from the recurrent and external 

 laryngeal nerves. 



The middle cardiac nerve is described with the other cardiac nerves. 



The INFERIOR CERVICAL GANGLION is situated between the base of the trans- 

 verse process of the last cervical vertebra and the neck of the first rib, on the 

 inner side of the superior intercostal artery. Its form is irregular ; it is larger in 

 size than the preceding, and frequently joined with the first thoracic ganglion. 



Its superior branches communicate with the middle cervical ganglion. 



Its inferior branches descend, some in front of, others behind, the subclavian 

 arterv, to join the first thoracic ganglion. The most important of these branches 

 constitutes the inferior cardiac nerve, to be presently described. 



The external branches consist of several filaments, some of which communicate 

 with the seventh and eighth spinal nerves; others accompany the vertebral 

 artery along the vertebral canal, forming a plexus round this vessel, supplying 

 it with filaments, and communicating with the cervical spinal nerves as high as 

 the fourth. 



CAROTID AND CAVERNOUS PLEXUSES. 



The Carotid Plexus is situated on the outer side of the internal carotid. Fila 

 ments from this plexus occasionally form a small gangliform swelling on the under 

 surface of the artery, which is called the carotid ganglion. The carotid plexus 

 communicates with the Casserian ganglion, with the sixth nerve, and spheno- 

 palatine ganglion, and distributes filaments to the wall of the carotid artery, and 

 to the dura mater (Valentin). 



The communicating branches with the sixth nerve consist of one or two fila- 

 ments, which join that nerve as it lies upon the outer side of the internal carotid. 

 Other filaments are also connected with the Casserian ganglion. The communica- 

 tion with the spheno-palatine ganglion is effected by the carotid portion of the 

 Vidian nerve, which passes forwards, through the cartilaginous substance filling 

 in the foramen lacerum medium, along the pterygoid canal, to the spheno-palatine 

 ganglion. In this canal it joins the petrosal branch of the Vidian. 



The Cavernous Plexus is situated below, and to the inner side of, that part of the 

 internal carotid, which is placed by the side of the sella Turcica, in the cavernous 

 sinus, and is formed chiefly by the internal division of the ascending branch from 

 the superior cervical ganglion. It communicates with the third, fourth, fifth, and 

 sixth nerves, and with the ophthalmic ganglion, and distributes filaments to the 

 wall of the internal carotid. The branch of communication with the third nerve 

 joins it at its point of division ; the branch to the fourth nerve joins it as it lies 

 on the outer wall of the cavernous sinus ; other filaments are connected with the 

 under surface of the trunk of the ophthalmic nerve ; and a second filament of 

 communication joins the sixth nerve. 



The filament of connection with the ophthalmic ganglion arises from the ante- 



