CoGHiLL, Cranial Nerves of Ambly Stoma. 251 



tral part ; while the communis X ganglion lies between the 

 lateralis and general cutaneous ganglia. The most anterior and 

 dorsal root of the complex is the lateralis X. Just posteriorly, 

 and considerably below the latter, arises the glossopharyngeal, 

 which is made up ot communis and motor fibers. The second 

 root of the vagus is communis and motor ; the third, com- 

 munis, motor and general cutaneous ; the fourth, motor. 



The t. glossopharyngeus is derived from the entire glosso- 

 pharyngeal root and from the general cutaneous ganglion of 

 the third vagus root. One division of the general cutaneous 

 component of this nerve passes into the r. jugularis VII, via 

 r. communicans IX + X ad VII. The remainder of this com- 

 ponent passes to the skin near the base of the first external gill 

 and of the dorsal surface of the gill itself. The motor compo- 

 nent of the nerve innervates the m. levator arcus branchii primi, 

 m. depressor branchii primi and m. ceratohyoideus internus. 

 The communis component forms Jacobson's anastomosis with 

 the r. palatinus caudalis, connects with the r. alveolaris VII 

 through the r. communicans IX + X ad VII, forms the r. pre-tre- 

 maticus and r. post-trematicus and pharyngeal rami. A twig 

 of these fibers, also, unites with the r. pre-trematicus of the 

 first truncus branchialis X. 



The general cutaneous ganglion of the vagus sends a large 

 component, also, into each of the first two branchial trunks of 

 the vagus. These fibers are distributed to the skin about the 

 base of the second and third gills and to the skin of the upper 

 surface of these gills. The communis component of these two 

 nerves is furnished by the second root of the vagus, as is also 

 their motor component. The former component forms the 

 typical pre- and post-trematic rami, and small pharyngeal rami. 

 The motor component innervates the second and third levator 

 muscles of the gill arches and the muscles of the three external 

 gills, excepting the first depressor branchii. The motor com- 

 ponent of the first branchial trunk passes, also, to the m. inter- 

 branchiales. 



The communis component of the vagus enters, also, the t. 

 visceralis. The fibers entering this trunk are derived from the 



