466 . Grace B. Watkinson 
b) Rami museulares. In its course over muse. hyoglossus many 
fine branches are given off posteriorally into this muscle. Others 
are given into muse. hyoideus and to the region of the thymus 
sland. 
c) Ramus laryngeus arises where the main stem of ©. crosses 
the hyoid bone dorsally. This branch passes anteriorally between 
muse. hyoideus and the pharynx wall to divide in a number of 
finer branches in the membrane of the anterior region of the pharynx. 
(Ramus lingualis seems to be entirely lacking in glossopharyn- 
geus and there are also no branches from this nerve to muse. genio- 
hyoideus, as in the birds. Both of these functions, however, are 
performed by strong branches from XII.) 
X. Nervus vagus arises from the mid-lateral line of the me- 
dulla oblongata in its posterior region, as a bundle of fine fihres 
which spread out, fan-shaped, along the side of the medulla. Before 
entering its foramen, vagus is joined hy the stem of nervus acces- 
sorious which comes from a posterior direction along the side of 
the spinal eord and enters the cranial cavity through the foramen 
magnum. Vagus then enters its own canal in the pleurooceipital 
bone where it is joined by the elements of hypoglossus (see XI.) 
and the two nerves emerge from the skull in a common stem and 
continue as such for a short distance outside of the skull. Here 
the nerves separate and vagus takes its course direetly posterior in 
association with the carotid artery to the thoracie region, where, 
near the carotid arch, a swelling, the ganglion trunci nervi vagi, 
oceurs. From this point the nerve passes ventral to the tracheal 
tube and ends in the several branches to the heart, lungs, and 
digestive tract. These branches are as follows: 
a) Ramus externus (deseribed under nervus accessorious), arises 
as soon as vagus has emerged from the skull and innervates muse. 
sternocleidohyoideus. 
b) Ramus com. cum nervo glossopharyngeo (described under IX.) 
arises from the main stem a short distance distal to (a). 
ec) Ramus eommunicans anterior cum nervo sympathico leaves 
ganglion trunei and conneets vagus with the cervical stem of nervus 
sympathieus, which lies close to it at this point. 
d) Ramus recurrens laryngeus is a portion of ramus laryngo- 
pharyngeus which arises a short distance posterior to ganglion 
trunei. It, (d), runs anterior close to the lateral wall of the trachea 
to the larynx where the larynx commissure (described under IX.) 
