THE CARDIAC PLEXUS. 805 



piercing the Diaphragm, terminates in the renal plexus and lower part of the 

 solar plexus. It occasionally communicates with the preceding nerve. 



A striking analogy appears to exist between the splanchnic and the cardiac 

 nerves. The cardiac nerves are three in number; they arise from the three 

 cervical ganglia, and are distributed to a large and important organ in the thoracic 

 cavity. The splanchnic nerves, also three in number, are connected probably with 

 all the dorsal ganglia, and are distributed to important organs in the abdominal 

 cavity. 



The Lumbar Portion of the Gangliated Cord. 



The lumbar portion of the gangliated cord is situated in front of the vertebral 

 column along the inner margin of the Psoas muscle. It consists usually of four 

 ganglia, connected together by interganglionic cords. The ganglia are of small 

 size, of a grayish color, shaped like a barleycorn, and placed much nearer the 

 median line than the thoracic ganglia. 



The superior and inferior branches of the lumbar ganglia serve as communi- 

 cating branches between the chain of ganglia in this region. They are usually 

 single and of a white color. 



The external branches communicate with the lumbar spinal nerves. From the 

 situation of the lumbar ganglia these branches are longer than in the other regions. 

 They are usually two in number from each ganglion, but their connection with the 

 spinal nerves is not so uniform as in other regions. They accompany the lumbar 

 arteries around the sides of the bodies of the vertebrae, passing beneath the fibrous 

 arches from which some of the fibres of the Psoas muscle arise. 



Of the internal branches, some pass inward, in front of the aorta, and help to 

 form the aortic plexus. Other branches descend in front of the common iliac 

 arteries, and join over the promontory of the sacrum, helping to form the hypo- 

 gastric plexus. Numerous delicate filaments are also distributed to the bodies of 

 the vertebrse and the ligaments connecting them. 



Pelvic Portion of the Gangliated Cord. 



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 together 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). 



The superior and inferior branches are the cords of communication between the 

 ganglia above and below. 



The external branches, exceedingly short, communicate with the sacral nerves. 

 They are two in number from each ganglion. The coccygeal nerve communicates 

 either with the last sacral or coccygeal ganglion. 



The internal branches 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, and others form a plexus which accompanies the 

 middle sacral artery and sends filaments to the coccygeal gland. 



THE GREAT PLEXUSES OF THE SYMPATHETIC. 



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

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

 cavities respectively. From them are derived the branches which supply the 

 viscera. 



The Cardiac Plexus. 



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 



