122 ANATOMY OF UPPER EXTREMITY, ETC. 



the lower part of the chest, where it again inclines to the 

 left, over the aorta, and passes through the oesophageal 

 opening of the diaphragm. 



The O3sophagus has a muscular and a mucous coat ; the 

 muscular coat is made up of longitudinal and circular 

 fibres, and is connected with the mucous by an intervening 

 layer of cellular tissue ; the mucous coat is of a pale color, 

 and moves freely upon the muscular, the contraction of 

 which throws it into longitudinal folds. 



The SYMPATHETIC NERVE consists of two portions. The 

 first is the prevertebral portion, made up from the cardiac 

 nerves, descending from the cervical ganglia (p. 53), the 

 branches of which, uniting with filaments from the recur- 

 rent laryngeal and pneumogastric nerves, form the cardiac 

 and pulmonary plexuses, distributed over the origin of the 

 great vessels of the heart, and to the heart itself, the root 

 of the lungs, and the trachea. These can only be satisfac- 

 torily studied by special dissections. 



The second or vertebral portion of the sympathetic, con- 

 sists of a chain of twelve connected ganglia, situated near 

 the heads of the ribs, covered in by the pleura, and continu- 

 ous with those of the neck and abdomen. The upper gan- 

 glion is the largest, and the two lower are anterior to the 

 line of the others. Each ganglion furnishes a branch to the 

 intercostal nerves, and from the upper six, small branches 

 are sent to the aorta and mediastinum. Branches from 

 the sixth, seventh, eighth, and ninth, unite to form the 

 great splanchnic nerve, which passes through the dia- 

 phragm, by the side of its crus, to join the semilunar gan- 

 glion. Branches from the tenth and eleventh ganglia form 

 the lesser splanchnic nerve, which, piercing the diaphragm, 

 goes to join the renal and coeliac plexuses. A branch from 

 the twelfth ganglion, occasionally communicating with the 

 preceding nerve, also pierces the diaphragm, and joins the 

 renal and coeliac plexuses, under the name of the third or 

 renal splanchnic nerve. 



The INTERCOSTAL NERVES, twelve upon each side, are the 

 anterior branches of the spinal nerves of the dorsal region. 

 They pass forward between the two muscular layers of 

 the intercostal space, perforating the external muscle an- 

 teriorly, to be distributed to the integument of the front of 

 the thorax. Each nerve receives a short branch from the 

 ganglionic trunk of the sympathetic. The first intercostal 

 nerve sends a large branch to join the brachial plexus ; the 



