THE GEE AT SYMPATHETIC NERVOUS SYSTEM. 891 



5. On the right side are two principal cardiao nerves, and four secondary 

 filaments. The first cardiac nerve is a long branch that arises at fhe middle 

 cervical ganglion. It is formed by fibres from the sympathetic, and by a 

 fasciculus furnished by the right pneumogastric, at the entrance to the thorax ; 

 it also probably receives medullary fibres through the medium of a communicating 

 branch between the middle and inferior ganglion. This nerve is reinforced by 

 two filaments that proceed from the inferior cervical ganglion, and sometimes 

 from the second middle ganglion, one of which — the posterior — is itself reinforced 

 by a left sympathetic filament that reaches its destination in passing along the 

 recurrent nerve. When it is entirely constituted, the first nerve creeps on the 

 base of the heart, turns round the arch of the aorta, and mixes its terminal fibres 

 with those of the left cardiac nerves. The second right cardiac nerve is formed 

 by the union of tkree branches that arise successively from the corresponding 

 pneumogastric, behind the dorsal artery, along the right side of the trachea. 

 This nerve attaches itself to the sympathetic in the dorsal region, by three 

 branches that approach the latter below the first, fourth, and sixth ribs. 



When the second right nerve arrives above the termination of the anterior 

 vena cava, it divides into two branches ; one of tnese goes to the roof of the 

 auricles, and the other — joined by a filament from the pneumogastric — is 

 expended by numerous ramuscules, on the surface of the left ventricle ; some 

 even extend to the right ventricle. 



The four secondary filaments are echeloned on the portion of the pneumo- 

 gastric included between the entrance to the thora'x and the division of the 

 bronchi, These filaments go to the large vessels, and into the walls of the heart.^ 



3. Dorsal Portion of the Sympathetic. 



The cord represented by this portion of the sympathetic chain leaves the 

 inferior cervical ganglion, and extends from before to behind, towards the 

 diaphragm, passing beneath the superior extremities of the ribs — or rather, below 

 the vertebro-costal articulations, against which it is maintained by the pleura — 

 and crossing the intercostal arteries. It is continued in the abdominal cavity by 

 the lumbar portion, after passing through the arch in the superior border of the 

 diaphragm, along with the psoas parvus. 



Along its course, this cord exhibits, at each intercostal space, a small fusiform 

 ganglionic enlargement — seventeen in all. The two or three first are most 

 frequently absent ; but then the anterior extremity of the nerve has for some 

 extent the appearance of a ribbon-shaped ganglion, which seems to be due to the 

 elongation, posteriorly, of the inferior grey mass of the cervical portion. 



Afferent Branches. — Furnished by the inferior branches of the dorsal 

 nerves, these ramuscules number from one to three for each ganglion. In 

 proceeding from the intervertebral foramina to the sympathetic, they traverse the 

 superior extremity of the intercostal space, passing sometimes behind, sometimes 

 before, the arteries of that name. 



Efferent Branches. — A very few delicate branches pass to the pleurae ; 

 those which demand notice are the great and lesser splanchnic nerves. 



• To sum up — the cardiac nerves contain fibres from the pneumogastrics. The rifjht 

 pneumogastric furnishes a greater number to them tkan the left. Perhaps to this circumstance 

 is due the predominance of the right vagus in the phenomena attending arrest of the heart's 

 action (Arloing and Tripier, " Contribution a la Physiologie des Nerfs Vagues," in Archiv. de 

 Phyeiologie Nor. et Path. 1872). 



