THE CARDIAC PLEXUS 1075 



of the vertebrae, passing beneath the fibrous arches from which some of the fibres 

 of the Psoas magnus arise. 



Of the branches of distribution some branches pass inward, in front of the aorta, 

 and help to form the abdominal aortic plexus (plexus aorticus abdominalis) (Fig. 

 780). Other branches descend in front of the common iliac arteries, and, joining 

 over the promontory of the sacrum, assist in forming the hypogastric plexus (plexus 

 hypogastricus) (Fig. 780). Numerous delicate filaments are also distributed to 

 the bodies of the vertebra? and the ligaments connecting them. 



Pelvic Portion (Pars Pelvina) of the Gangliated Cord (Fig. 780). 



The pelvic portion of the gangliated cord is situated in front of the sacrum 

 along the inner side of the anterior sacral foramina. It consists of four or five 

 small ganglia on each side, connected by interganglionic cords. Below, these 

 cords converge and unite on the front of the coccyx by means of a small ganglion, 

 the coccygeal ganglion or ganglion impar (ganglion coccyyeum impar) (Fig. 780). 



Gray rami communicantes pass from the ganglia to the sacral and coccygeal 

 nerves. No white rami communicantes join this part of the gangliated cord, 

 but the visceral branches which arise from the third and fourth, and sometimes 

 from the second, sacral are regarded as homologous w r ith white rami communi- 

 cantes 



The branches of distribution communicate on the front of the sacrum with the 

 corresponding branches from the opposite side; some, from the first two ganglia, 

 pass to join the pelvic plexus, while others form a plexus which accompanies the 

 middle sacral artery, from which plexus filaments pass to the coccygeal gland. 



THE GREAT PLEXUSES OF THE SYMPATHETIC SYSTEM. 



The great plexuses of the sympathetic are the large aggregations -of nerves 

 and ganglia, previously alluded to, situated in the thoracic, abdominal, and pelvic 

 cavities respectively, and named the cardiac, pulmonary, oesophageal, coeliac, and 

 hypogastric plexuses respectively. They consist not only of sympathetic fibres 

 derived from the ganglia, but also of fibres from the central nerve system which 

 are conveyed through the white rami communicantes. From them are derived 

 the branches which supply the viscera. 



The Cardiac Plexus (Plexus Cardiacus) (Fig. 780). 



The cardiac plexus is situated at the base of the heart, and is divided into a 

 superficial part, which lies in the concavity of the arch of the aorta, and a deep 

 part, which lies between the trachea and aorta. The two plexuses are, however, 

 closely connected. 



The superficial cardiac plexus lies beneath the arch of the aorta, in front of 

 the right pulmonary artery. It is formed by the left superior cardiac nerve, the 

 left (and occasionally also the right) inferior cervical cardiac branches of the vagus. 

 and filaments from the deep cardiac plexus. A small ganglion, the cardiac ganglion 

 of Wrisberg (ganglion cardiacum [Wrisbergi]) is occasionally found connected with 

 these nerves at their point of junction. This ganglion, when present, is situated 

 immediately beneath the arch of the aorta on the right side of the ductus 

 arteriosus. The superficial cardiac plexus gives branches to the deep cardiac 

 plexus beneath the arch of the aorta to the right or anterior coronary plexus and 

 to the left anterior pulmonary plexus. 



The deep cardiac plexus is situated in front of the trachea at its bifurcation. 



