THE CERVICAL PLEXUS. 



1291 



a. The pleural branches, two in number, are almost microscopic in size, and are given 

 off as the nerve crosses the apex of the pleura. One supplies the costal pleura and the other, 

 which sometimes accompanies the internal mammary artery, is distributed to the medias- 

 tinal pleura. 



b. The pericardiac branch (r. pericardiacus) is a tiny filament which is usually given off 

 opposite the lower margin of the third costal cartilage. It is sometimes absent on the left side. 



c. The terminal branches arise under cover of the pleura and differ to some extent on 



the two sides. 



The right phrenic divides antero-lateral to the opening for the inferior vena cava into ( ad) 



an anterior and {bb) a posterior branch. 



aa. The anterior branch breaks up under the pleura into five or six fine twigs, which spread 

 out antero-laterally in the sternal portion and the anterior part of the right costal portion of the 



Fig. 1090. 



Scalenus medius muscle' 



Vagus nerve 



V. cervical nerve 



Scalenus anticus muscle 



Upper trunk of brachial plexus 

 VII. cervical nerve 

 Superior intercostal artery 

 Vni. cervical nerve 

 I. thoracic nerve 

 Clavicle 



• 



Phrenic nerve 



Internal mam- 

 mary artery 



Innominate veins 



Vena cava superior 



Lung, mesial surface 



Sterno-cleido-mastoid 



Vagus nerve 

 Internal jugular vein 

 Subclavian artery 

 Omo-hyoid muscle 



Subclavian vein 

 Clavicle 



Subclavius muscle 



I. rib 



Manubrium stemi 

 Vagus nerve 



—7— Phrenic nerve 



Pericardium 



ngr. mesial surface, 

 showing hilum 



Sternum 



— IV. rib 



Diaphragm, up- 

 per surface 



VII. rib 



Dissection showing phrenic nerves ; parts of sternum and ribs have been removed ; lungs are pulled aside ; 



pericardium is undisturbed. 



diaphragmatic musculature. Tiny filaments traverse the interval between the sternal and costal 

 portions and enter the abdomen, where they are distributed to the peritoneal covering of the 

 .diaphragm and to the falciform ligament of the liver in the direction of the umbilicus. 



bb. The posterior branch pierces the central tendon at the outer margin of the quadrate 

 opening and divides into a muscular hx-Anc\\ and the right phrcnico-ahdoniifial branch (r. phrenicO' 

 abdominalis dexter). The former supplies the lumbar portion of the musculature of the diaphragm. 

 The latter traverses the quadrate foramen and first gives off a recurrent branch which accompanies 

 the inferior vena cava back to the right auricle. After giving off this branch, under cover of the 

 peritoneum some of its fibres ^nier \he diaphragmatic ganglion and others unite with filaments 

 from the cceliac plexus to form at the inferior surface of the diaghragm the diaphragmatic 

 plexus, which is joined by twigs from the diaphragmatic ganglion. From this plexus fibres 

 are distributed to the coronary ligament and peritoneum of the liver and to the right supra- 

 renal body. 



The left phrenic pursues a general antero-lateral course and pierces the diaphragm at the 

 junction between the musculature and the central tendon. Under cover of the peritoneum it 

 splits up into an anterior, a lateral and a postenoi branch. The anterior branch supplies the 

 muscle of the left sternal portion and the antero-late-al part of the left costal portion. The 



