632 THE SYMPATHETIC XEEVES AXD GANGLIA. 



the chest it follows the left carotid artery to the arch of the aorta, and 

 ends in some instances in the superficial cardiac plexus, while in others 

 it joins the deep plexus ; and accordingly it passes either in front of or 

 behind the arch of the aorta. 



4. BRANCHES TO BLOOD-VESSELS. — The nervcs which ramify on the 

 arteries (nervi molles) spring from the front of the ganglion, and 

 twine round the trunk of the carotid artery. They are also pro- 

 longed on the branches of the external carotid, and form slender 

 plexuses upon them. 



Communications with other nerves. — From the plexus on the facial artery 

 is derived the filament which joins the sulmiaxillary ganglion ; and. from that on 

 the middle meningeal artery, twigs have been described as extending to the otic 

 ganglion, as well as to the gangUform enlargement of the facial nerve. Lastly, 

 a communication is established between the plexus on the carotid artery and the 

 digastric branch of the facial nerve. 



Varieties. — Small ganglia are occasionally found on some of the vascular 

 plexuses, close to the origin of the vessels with which they are associated. Thus 

 lingual, temporal, and pharyngeal ganglia have been described ; and besides these 

 there is a larger body, the ganglion inter caroticum, placed on the inner side of 

 the angle of division of the common carotid artery. This body, long known to 

 anatomists as a ganglion, has been stated by Luschka to have a structure very 

 different from the nervous ganglia in general, and has been named by him the 

 " glandula intercarotica."' 



It is described by him as presenting principally a follicular structure, similar to 

 that of the glandula coccygea, which he had previously discovered. It appears, 

 however, from the researches of Julius Arnold, that the foUicidar appearances 

 observed by Luschka, both in this instance and in the coccygeal gland, were pro- 

 duced by arterial glomeruli seen in section ; and that the ganglion intercaroticum 

 consists of numbers of those glomeruli gathered into several larger masses, and of 

 dense plexuses of nerves surrounding respectively the glomeruli, the masses, and the 

 whole structure. Within those plexuses nerve-cells are scattered, but not in very 

 great number. The ganglion is usually about one-fourth of an inch long ; but. 

 according to Luschka, may be divided into small separate masses, and thus escape at- 

 tention, or be supposed to be abseiat. — (Luschka, " Anat. d. Menschen," vol. i. 18G2 ; 

 and Julius Arnold, in '' Yirchow's Archiv," June, 1865.) 



MIDDLE CERVICAL GANGLION. 



The middle ganglion (ganglion thyroideum), much the smallest of the 

 cervical ganglia, is placed on or near the inferior thyroid arterj'. It is 

 usually connected with the fifth and sixth spinal nerves, but in a some- 

 what variable manner. It gives oft' 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. Whilst on the artery, these branches communicate with the 

 upper cardiac nerve. 



The middle cardiac nerve (nervus cardiacus profundus v. magnus) 

 of the right side is prolonged to the chest behind the sheath of the 

 common carotid artery, and either in front of or behind the subclavian 

 artery. In the chest it lies on the trachea, where it is joined by fila- 

 ments of the recurrent laryngeal nerve, and it ends in the right side of 

 the deep cardiac plexus. While in the neck, the nerve communicates 

 with the upper cardiac nerve and the recurrent branch of the pneumo- 

 gastric. 



