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head arise from the medulla by two roots, a dorsal root from the 
lateral line lobe and a more ventral one from the acusticum. The 
dorsal island in the medulla of Necturus and Amphiuma seems to be 
the representative of the lateral line lobe of fishes, for into it passes 
the dorsal rootlet of the dorsal VII nerve, while the more ventral 
rootlets enter the underlying sensory column. In Amphiuma the 
dorsal island extends from a level a little posterior to the point of 
entrance of the lateralis root of the vagus nerve into the medulla 
to a level a little anterior to the entrance of the dorsal rootlet of 
the dorsal VII. Of the three rootlets of the dorsal VII the dorsal 
enters the brain a little posterior to the level of the others. In 
Amblystoma, according to Coghill , 3 the dorsal rootlet corresponds 
to the ophthalmicus superficialis VII. In Acanthias, according to 
Strong , 4 it is the mandibularis externus VII (mentalis VII) and 
buccalis VII branches that are related to the dorsal root, while the 
ophthalmicus superficialis VII enters chiefly the ventral root. 
Kingsbury 5 says that in Necturus the two roots of the dorsal VII 
do not correspond to divisions between the portions that join the V 
and VII nerves. In Amphiuma because of the intertwining of the 
fibers of the various rootlets it is difficult to distinguish between the 
portions that correspond to the different branches. Apparently 
the dorsal rootlet is derived largely from the mentalis VII (man- 
dibularis externus VII) , but the preparations do not permit exact 
statements in this regard. 
From the points of entrance of the rootlets into the brain the 
root of the dorsal VII passes anteriorly as a flattened band closely 
compressed between the brain and the skull. From its ventral 
border many fibers pass antero-ventrally into the acustico-facial 
ganglion, a complex of ganglion cells from the auditory nerve, from 
the communis component of the VII nerve, and from the descending 
lateralis fibers just mentioned. The lateralis ganglion cells occupy 
the anterior ventral part of the mass, some of the cells crowding 
out a short distance with the exit of the VII nerve. As the VII 
nerve leaves the skull the lateralis component occupies the dorsal 
anterior part of the nerve trunk, and as the latter passes posteriorly 
comes to lie on the dorsal lateral border. 
3. Coghill, G. E. The Cranial Nerves of Amblystoma tigrinnm. Jour. Compar, 
Neurol., Vol. 12, No. 3, 1902. 
4. Strong, O. S. The Cranial Nerves of Squalus acanthias. Abstract. Science, N. S.. 
Vol. 17, No. 424, 1903. 
5. Kingsbury, B. F. On the Brain of Necturus maculatus. Jour. Compar. Neurol., 
Vol. [5, 1895. 
