MIDDLE AND LOWER CERVICAL GANGLIA. 365 



is derived the filament which forms the sympathetic root of the subinaxillaiy 

 ganglion ; and from that on the middle meningeal artery twigs are described as extend- 

 ing to the otic ganglion, as well as to the geniculate ganglion of the facial nerve 

 (external superficial petrosal nerve, p. 253). One filament descends from these 

 nerves to the carotid gland. 



Microscopic ganglia are frequently met with in the vascular plexuses, and several larger 

 ones of more constant occurrence have been described. The most important of these is 

 the tciu/)or<il (/uixjlion, about 2 mm. in length, situated on the external carotid artery at the 

 place of origin of the posterior auricular branch ; it is said to receive a filament from 

 the stylo-hyoid branch of the facial nerve. 



MIDDLE CERVICAL GANGLION. 



The middle ganglion, much the smallest of the cervical ganglia, is placed on the 

 sympathetic cord at or near the spot where it crosses the inferior thyroid artery, 

 about opposite the sixth or seventh cervical vertebra. It is usually connected by grey 

 branches with the fifth and sixth spinal nerves, but in a somewhat variable 

 manner. It gives off thyroid branches and the middle cardiac nerve. 



Thyroid branches. From the inner side of the ganglion some twigs proceed 

 along the inferior thyroid artery to the thyroid body, where they join the recurrent 

 laryngeal and the external laryngeal nerves. While on the artery, these branches 

 communicate with the upper cardiac nerve. 



The middle cardiac nerve (deep or great cardiac nerve) of the right side is 

 prolonged to the chest either in front of or behind the subclavian artery. In the 

 chest it lies on the trachea, where it is joined by filaments of the recurrent laryngeal 

 nerve, and it ends in the right side of the deep cardiac plexus. While in the neck, 

 this nerve communicates with the upper cardiac nerve and the recurrent branch of 

 the pneumo-gastric. 



On the left side, the middle cardiac nerve enters the chest between the left carotid 

 and subclavian arteries, and joins the left side of the deep cardiac plexus. 



Varieties. The middle cervical ganglion is often absent, and in that case the middle 

 cardiac nerve is given off by the interganglionic cord. On the other hand, it is sometimes 

 double (fig. 233). The smaller upper portion (A) is the middle cervical ganglion of Arnold 

 and Luschka, the thyroid ganglion of Krause ; while the larger lower portion (B) is the 

 middle cervical ganglion of Swan and Krause, the inferior cervical ganglion of Arnold, 

 Luschka, and Riidinger. The single ganglion is more frequently in the latter situation. 



This part of the cord is sometimes placed behind the inferior thyroid artery, or it may be 

 divided so that the artery is enclosed in a loop of the nerve. 



LOWER CERVICAL GANGLION. 



The lower cervical ganglion is irregular in shape, usually somewhat flattened 

 and round, or semilunar, and is frequently united to the first thoracic ganglion, the 

 common mass being described as the first thoracic ganglion by many authors. It lies 

 over the first costo-central articulation, in the lateral angle between the subclavian and 

 vertebral arteries. The connecting cord between the middle and lower cervical 

 ganglia usually passes behind the vertebral artery, but in some cases, especially on 

 the left side, the interganglionic cord forms a ring around the vessel. The two- 

 ganglia are also united by the ansa subclavia (see below). 



The inferior cervical ganglion is connected to the lowest two cervical nerves by 

 grey communicating branches, and it gives off the lower cardiac nerve and offsets to 

 blood-vessels. 



The lower cardiac nerve, issuing from the inferior cervical ganglion, or from 

 the first thoracic, inclines inwards on the right side, behind the subclavian artery 

 and terminates in the cardiac plexus behind the arch of the aorta. It communicates 



VOL. III.. PT. 2. * A 



