382 NERVOUS SYSTEM. 
the right subclavian artery just caudad of the origin of the 
internal mammary artery, then passes to the trachea, and has 
a course and distribution like that of the left side. 
On reaching the root of the lungs the vagus divides into 
numerous branches which form the pulmonary plexus (£) over 
the roots of the lungs, and extends onto the basis of the heart 
as the cardiac plexus. From these plexuses numerous 
branches pass to the heart, lungs, pulmonary artery, pericar- 
dium, etc. The cardiac branches from the sympathetic, men- 
tioned above, are also connected with the cardiac plexus. 
Caudad of the pulmonary plexus the vagus is continued 
on each side as two trunks, a dorsal (sz) and a ventral (/) 
which pass along the cesophagus (~). The ventral branches 
of right and left vagi (¢ and 7’) unite a short distance caudad 
of the root of the lung, and the single trunk extends into the 
abdominal cavity on the ventral surface of the cesophagus. 
The dorsal branches of right and left vagi unite farther back, 
near the diaphragm, and the single trunk thus formed (#2) 
enters the abdominal cavity on the dorsal surface of the 
cesophagus. Both divisions give fine nerves to the cesophagus. 
Abdominal Portion of the Vagus (Fig. 164, page 407).— 
After passing through the diaphragm the ventral division (Fig. 
164, 7) reaches the lesser curvature of the stomach (1), over 
which it ramifies, some branches being traceable almost to the 
pylorus. The network of branches thus formed is the anterior 
gastric plexus. Some twigs from the ventral division pass 
transversely across the cranial end of the stomach and join the 
plexus formed by the dorsal division. 
The dorsal division (#) of the vagus reaches the greater 
curvature of the stomach, where it ramifies, forming the pos- 
terior gastric plexus. Branches from this anastomose with 
the anterior gastric plexus and with the cceliac plexus of the 
sympathetic (¢). 
XI. N. ACCESSORIUS.—The accessory (or spinal accessory) 
nerve arises (Fig. 138, X/) by numerous rootlets from the 
lateral surface of the medulla and of the spinal cord as far 
caudad as the fifth to seventh cervical nerve. These spinal 
rootlets join to form a nerve which enters the cranium through 
