^4 bulletin: museum of comparative zoology. 



the lateral surface of the medulla a few sections anterior to the fora- 

 men. Its fibers enter the brain at a sharp upward angle. The coarser 

 fibers of the posterior root remain together and may be traced as they 

 pass mesad in a broad upward curve to become spread out in the midst 

 of a group of cells lying a little dorsal and lateral to the fasciculus 

 solitarius. The more lightly medullated components of this root 

 could be found making continuous connection with the fasciculus 

 solitarius, into which they abruptly turn. The other two roots enter 

 the brain along the same line as the posterior one. The smaller 

 one could not be followed, but the larger could be traced to the 

 fasciculus solitarius. It also contained several coarse fibers, which 

 take the same direction as those of like character in the posterior 

 root. The three roots remain separate until they enter the jugular 

 ganglion. 



The ganglion jugulare, or root ganglion of the vagus (Plates 2, 3, 

 figs. 4, 5, 6, gn. rx. X), Plates 3, 7, figs. 7, 22, gn. X), lies closely 

 crowded into the angle formed betw,£^ the otic capsule and the 

 basioccipital where the jugular foramen opens. This foramen appears 

 in the same transverse section as the first occipital foramen of XII 

 (Plate 7, fig. 20). The ganglion which is larger than that of IX or 

 VII, is triangular in transverse sections of the head (Fig. 22, gn. X). 

 This form is the result of the pressure of surrounding structures, the 

 ganglion being crowded against the otic capsule by the spinalis colli 

 muscle (Plate 7, fig. 22, spi. coll.). The form of the ganglion as a 

 whole is notable, owing to the fact that the ganglion cells are so 

 grouped on the mesial side of the fiber bundle that in dissections 

 (Plate 3, fig. 7) the ganglion appears to lie free along the root 

 bundles for a short distance. 



The fibers entering the ganglion as separate roots emerge on its 

 distal side as one bundle, the coarse motor fibers, about sixteen in 

 number, being grouped in its dorsal portion. This bundle (A') passes 

 caudad parallel with IX and XII (Plates 2 and 3). On its way it 

 shows the small ramus connecting it with IX (Plates 2 and 3, figs. 

 4, 7, com7i. IX-X). Posterior to the ganglion of IX, the trunk of 

 the vagus divides into a sujicrior laryngeal ramus and a visceral ramus 

 {mc. X.). The superior laryngeal ramus soon joins the pharyngeal 

 ramus of IX to form the phar\Tigo-laryngeal ramus of IX + X (Plate 

 2, fig. 4, phx-lar.). This then combines with the trunk of XII (fig. 7) 

 to reach the ventral side of the pharynx, {cf. fig. K) . 



(a) Ramus laryngeus superior {lar. su.). This division of the vagus 

 includes all the coarse fibers of the main trunk and about one half 



