3. Inferior cervical ganglion, varies in its size and form, which, in general, is more or less semilunar ; its convexity being directed downwards, its concave margin upwards. It is situated between the transverse process of the seventh cervical vertebra and the neck of the first rib, behind the subclavian artery, and behind and to the outer side of the root of the vertebral artery. (a) Branches of com munication pass between the ganglion and the seventh and eighth cervical nerves, as well as the first intercostal nerve. It also sometimes communicates with the phrenic nerve and recurrent laryngmal. (b) From the ganglion proceed several fine twigs, which surround the subclavian artery as well as its branches, forming small plexuses about them. One of these accompanies the vertebral ar teries ; according to some it passes up along with the artery into the cranium, subdividing into as many secondary plexuses as there are branches of the artery. Blandin states that he has followed the branches of the nerve along the basilar artery, upon the posterior cerebral and cerebellar arteries. Whilst situ ated within the canal in the transverse pro cesses of the cervical vertebra it communi cates with several of the cervical nerves. According to Pei. De Blainville several gan glia occur on this branch, equal in number to the cervical vertebrce, and hence he regards the vertebral branch as the continuation up wards of the syn-tpathetic cord. According to Bourgery*, the common s3mpathetic trunk may be regarded as dividing at the inferior cervical ganglion into an anterior and a pos terior portion; the former, corresponding to the continuation of the cord in the neck, he terms the carotid track, the latter, correspond ing to the vertebral branch, he terms the pos terior or vertebral track. He describes it as arising from the plexus formed around the subclavian artery : it is quite visible to the naked eye at its origin, but higher up its filaments become microscopic in point of size : the vertebral branches, or tracks of opposite sides, unite together in the groove lodging the basilar artery, and communica tions are also formed between them and the anterior, or carotid track, by rneans of fila ments which pass backwards with the pos terior communicating arteries. The vertebro basilar nervous apparatus, as it is termed by him, supplies nerves to the vessels, which ramify on the cerebellum and posterior lobe of the cerebrum.
(c) Inferior or small Cardiac Nerve.— The inferior cardiac arises by one or two roots, passes inwards behind the subclavian artery, and terminates in the deep cardiac plexus. It forms communications with the middle car diac nerve, as also with the cardiac branch of the recurrent laryn,geal. Frequently, espe cially on the left side, the lower cardiac branch becomes united with the middle car tliac, giving rise to what has been termed the Nervus cardiacus crassus. The communi cating branch between the lower cervical and first thoracic ganglion is very short, some times wanting, the two ganglia running into one another.
I I. Thoracic portion of the Gangliated Cord. —The thoracic portion of the gangliated cord of the sympathetic lies on each side of the spinal column, in front of the transverse pro cesses of the vertebrm and heads of the ribs, and beneath the pleura. It is continuous above with the cervical portion, and below it pa.sses into the abdomen, between the pil lars of the diaphrag,m and superior extremity of the psoas muscle, outside the splanchnic nerves, becoming continuous with the lumbar portion of the s3mpathetic cord. The num ber of the ganglia varies : they are cominonly eleven, rarely twelve, on each side. They are, in general, situated between the heads of the ribs in front of the transverse processes of the vertebrm, and present commonly a more or less triangular form. The cord connecting the ganglia of either side runs in front of the heads of the ribs, and is ge nerally single, though sometimes it is double. The branches connected with the thoracic ganglia are the following: — (a) Communicating branches pass between each of the ganglia and the corresponding intercostal nerve : these are commonly double, sometimes three, short, and pretty strong.
(b) Branches of small size pass frorn the ganglia to the descending aorta, forming a plexus around it ; others pass to the pul monary and cesophageal plexuses ; branches are also described by Krause as passing be tween the ganglia of opposite sides in front of the bodies of the vertehrm.
(c) The chief branches leaving the thoracic ganglia are the greater and smaller splanchnic nerves. These are situated to the inner side of the main cord of the sympathetic, and also more anteriorly, upon the lateral and anterior surface of the bodies of the vertebrce. They are formed of branches derived from the six lower thoracic ganglia, and pass through the diaphragm into the abdomen. The greater splanchnic nerve derives its roots commonly from the inner part of the sixth, seventh, eighth, and ninth, thoracic ganglia ; it often also receives a branch from the fifth, and, according to Dr. Beck, from the different ganglia as high up as the first. It passes obliquely downwards and slightly inwards upon the sides of the vertebral column, in front of the intercostal vessels, and covered by the pleura. It enters the cavity of the abdomen by perforating the pillars be tween the middle and internal crura of dia phragm, rarely through the aortic opening, and terminates in the semilunar ganglion of the cceliac plexus. The stnaller splanchnic nerve, which is sometimes double, springs from the tenth and eleventh thoracic ganglia : following the same course as the greater splanchnic nerve, it is directed obliquely downwards and inwards upon the body of the twelfth dorsal vertebra, passes through the diaphragm between the greater splanchnic nerve and the comniunicating cord, wbich unites the last thoracic to the first lumbar ganglion, or pierces the middle crus of the It terminates in the cceliac and renal plexuses; the branch to the latter being generally stronger than that to the forrner.
(d) The communicating cord between the last thoracic ganglion and first lumbar enters the cavity of the abdomen between the middle and external crura of the dia phragm, or penetrates the latter.
III. Lumbar portion of the Gangliated Cord. — The lumbar portion of the sympathetic cord generally contains five ganglia, some times only three or four, and is situated upon the lateral and anterior aspect of the bodies of the lumbar vertebrm, in front of the psoas muscle, behind and to the left of the aorta on the left side, and behind and to the right of the vena cava on the right. The branches connected with the lumbar ganglia are :—(a) Branches of communication with the lumbar nerves: these are commonly two in number for each ; they are longer than those in the thoracic region, and pass between the heads of the psoas muscle.—(b) Branches also pass off from the ganglia to the aortic, spermatic, renal and superior hypogastric plexuses.— (c) Krause describes branches as passing across the bodies of the vertebrm, forming a com munication between the ganglia of opposite sides.
IV. Sacral portion of the Ganghated Cord.
— The sacral portion of the sympathetic cord is situated towards the inner side of the sacral foramina. The ganglia are commonly four in number, are smaller than those in the lumbar region, and decrease in size from above downwards : the cords of opposite sides con verge as they pass to the lower extremity of the sacrum, and unite together in front of the coccyx, there being frequently present at their point of union a small ganglion, from which one or two filaments of communica tion pass to the fifth sacral and coccygeal nerves. The branches connected with the sacral ganglia are communicating branches with the spinal nerves, commonly two in number for each. Several delicate filaments are also sent to the inferior hypogastric plexus.