UPPER NINE SPINAL NERVES. 493 



Of the Phrenic Nerve. 



The Phrenic Nerve (Nervus Phrenicus, Diaphragmaticus) 

 arises, in the manner stated above, from the anterior fasciculus 

 of the second and of the third cervical, and is assisted generally 

 by two or three filaments from the upper part of the brachial 

 plexus. It descends, vertically, on the humeral side of the in- 

 ternal jugular vein, but removed a considerable distance from it, 

 and is attached, by cellular substance, to the front of the scale- 

 nus anticus muscle. Getting, in its descent, to the internal mar- 

 gin of the latter, it passes into the thorax, at the inner margin 

 of the first rib, between the subclavian artery and the subclavian 

 vein, the latter being before it. It then goes along the superior 

 mediastinum to the pericardium, to the side of which it adheres 

 in front of the root of the lung, being between the pericardium 

 and the corresponding portion of the pleura; it finally reaches 

 the diaphragm, to which it is distributed. 



Just before the phrenic nerve reaches the diaphragm, it radi- 

 ates into several branches, which interchange filaments. Some 

 of the branches are distributed to the convex surface of the dia- 

 phragm; others penetrate the muscle, and are distributed in its 

 thickness and upon its concave surface. On the right side some 

 of these branches pass through the opening for the ascending 

 vena cava, and, thus getting into the abdomen, anastomose with 

 the solar plexus, and with the pneumogastric nerve. 



The phrenic nerve of the left side is nearer to the root of the 

 lung than that of the right, in consequence of the projection of 

 the apex of the heart on that side. Its distribution in other re- 

 spects does not present any remarkable difference from the other; 

 its branches radiate in the same way to the diaphragm, and sup- 

 ply its thickness, as well as its upper and under surfaces. It 

 sends some filaments to the lower part of the oesophagus. 



The phrenic gives off in the neck a few filaments to the sca- 

 lenus anticus, and the rectus anticus major muscle. It also com- 

 municates there, with filaments from the inferior cervical gang- 

 lion, and sometimes from the superior cervical. 



VOL. II. 43 



