THE VAGUS NERVM. 389 



sympathic (Fig. 107). From the ganglion of the trunk N. laryn- 

 geus superior (Fig. 107, N. I. sup.) may be traced entad of the 

 carotid to the larynx. 



§ 1033. N. hypoglossus (Fig. 107, iV. hpgls.).—A little cepha- 

 lad of the superior laryngeal nerve this will be seen crossing the 

 ectal surface of the carotid and extending to the tongue. 



§ 1034. N. glossopharyngeus (Fig. 107, N. gph., Plate II, Fig. 3, 

 N. gpTi. [ix]). — Divide the M. digastricus (Fig. 101) near its middle 

 and reflect the two ends. This will expose the bulla, and passing 

 along its caudo-mesal aspect will be seen the small glossopliaryn- 

 geal nerve. From its exit at the Fm. jugulare (Fig. 57, § 562), it 

 passes entad of the carotid on its way to the tongue. 



§ 1035. N. accessorius. — The spinal accessory may also be seen 

 piercing the sterno-mastoid muscle and passing latero-caudad from 

 the Fm. jugulare to be distributed to the ental surface of the clavo- 

 trapezius muscle (Fig. 104, 107, N. ac). 



% 1036. The path of the vagus through the foramen jugulare and 

 its relations with other nerves, also the ganglion of the root (Stow- 

 ell, 1), may be made out by nipping away the skull upon the 

 dorso-lateral side of the foramen. 



After the parts just described have been determined, the nerve 

 should be followed caudad. Near the 1st rib the sympathic inclines 

 laterad (Fig. 107). The vagus passes into the thorax entad of the 

 v. bracMo-cepJialica (Fig. 101, 109). 



§ 1037. Exposure of the Left Vagus in the Thorax. — Divide 

 the pectoral and other muscles, and costicartilages, about 1 cm. 

 from the meson, and turn the sternum dextrad, securing it with 

 chain hooks (§ 140) or strings. Then cut the left ribs with the nip- 

 pers about 2 cm. from their heads, and either remove this part of 

 the thoracic wall entirely or pin it down so that the thoracic cavity 

 shall be readily accessible. 



Cut the left brachio-cephalic vein and turn it mesad as shown in 

 Fig. 107. The sternal artery (§ 935) may be cut near the sternum 

 and pinned laterad. Then the vagus may be followed with the 

 tracer, fine forceps and fine scissors. ]N"ote the phrenic oierve 

 (§ 1019), which crosses the vagus just cephalad of the sternal artery. 

 The phrenic may be easily traced along the thorax ventrad of the 

 root of the lung to the diaphragm, by pulling upon it near where it 

 crosses the vagus, and turning the lungs to the left. 



