THE NERVOUS SYSTEM 



241 



thirteen pairs of thoracic ganglia, seven pairs of lumbar ganglia, 

 and one or two pairs of sacral ganglia, in addition to two median 

 unpaired sacral ganglia. 



In the cervical region the sympathetic and vagus, or tenth 

 cranial nerve, are bound in a 

 common sheath lying along the 

 lateral aspect of the carotid 

 artery. One or two centimeters 

 craniad of the first rib is the 

 thyroid or middle cervical gang- 

 lion, whence the nerve proceeds 

 in two cords, enclosing the sub- 

 clavian artery, to the large in- 

 ferior cervical ganglion just 

 caudad of the first rib. From 

 the cervical portions of the 

 sympathetic cord are given off 

 numerous delicate branches, 

 forming the carotid plexus on 

 the carotid artery, and uniting 



Fig. 116. — Chief Part of Left Half 

 OF Sympathetic System Craniad of 

 THE Diaphragm. Semidiagrammatic. 



5, 6, 7. 8, 9, and 10, Fifth, sixth, 

 seventh and eighth cervical nerves, and 

 first and second thoracic spinal nerves: 

 a, the dorsal branch of the left vagus 

 /n; an, dorsal branch of the right vagus; 

 ax, common dorsal vagus formed by a 

 and an; avb, ventral vagus; he, cardiac 

 branch of sg, cr; carotid plexus; car, 

 carotid artery; cm, rami communicantes; 

 cp, cardiac plexus; dia, diaphragm; g, 

 ganglia in the thoracic cavity; ig, mid- 

 dle cervical ganglion; Ig, portion of left 

 lung; In, left vagus nerve; nv, cranial 

 nerve; pn, phrenic nerve; pp, pulmo- 

 nary plexus; sn, sympathetic cord; sm, 

 superior cervical ganglion; sb, left sub- 

 clavian artery; sg, stellate ganglion or 

 inferior cervical; spin, splanchnic major 

 nerve; vg, vagus ganglion; v, vagus nerve. 

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