468 Grace B. Watkinson 
of the medulla oblongata in the region posterior to the vagus roots. 
These three roots pass through two small foramina from the cavum 
eranii, antero-laterally, and unite with the stem of vagus before 
it emerges from its foramen, so that all emerge as a single stem. 
This soon divides (as has been described under nervus vagus) into 
hypoglossus stem and vagus stem. The hypoglossus stem then 
receives its cerviecal element which consists of a branch from the 
united stem of the first and second cervical nerves. The remainder 
of this stem runs posterior, sometimes forming a partial union with 
vagus, and innervates musc. omo-hyoideus. This corresponds to 
»ramus descendens« of FISCHER but cannot be considered in this 
case a branch of hypoglossus, as it has no real union with the 
latter. After receiving this addition the nerve bends laterally, fol- 
lowing the line of glossopharyngeus, and running parallel to the 
latter nerve and posterior to it, passes over the ventral surface of 
muse. hyo-glossus, covered ventrally by muse. genio-hyoideus, to the 
point where glossopharyngeus passes dorsally over the anterior hyoid 
horn. Here hypoglossus passes ventral to the same and after giving 
off its posterior branch to muse. hyoideus, bends anteriorally and 
divides into its two end branches, one externally to the tongue 
itself. The branches of hypoglossus may be elassified as follows: 
A. Rami musculares. 
a) Ramus ad musculum genio-hyoideum is a strong branch 
given off posteriorally as the main nerve passes over the surface 
of this muscle on its way to the tongue. It spreads into a large 
number of fine branehes and innervates the muscle above named. 
b) Rami ad museulum hyo-maxillarem, is given off shortly distal 
to (a) and runs anteriorally across the ventral surface of nervus 
glossopharyngeus and the anterior hyoid horn to innervate the broad, 
flat, thin musele which eonnects this horn with the anterior region 
of the mandipble. 
B. Rami linguales comprise the main end branches of the 
nerve, as follows: 
a) Ramus lingualis posterior arises as has been above mentioned 
at the point where the nerve passes under the anterior hyoid horn. 
The branch turns posterior and sends off finer branches which enter 
muse. hyoideus at different points in its posterior region, the branch 
itself running through the same muscle along the region of its at- 
tachment to the posterior hyoid horn. 
b) Ramus lingualis anterior, the main end stem of the nerve 
