330 JOURNAL OF COMPARATIVE NEUROLOGY. 
The Ramus mandibularis externus passes cephalad and 
laterad around the lower edge of the squamosum to its outer 
surface, where it divides into branches, as in Necturus, one of 
‘which curves ventrally over the outer,surface of the M. depres- 
sor mandibuli and its tendon to run forward upon the ventral 
surface of the M. submaxillaris. The other division runs ceph- 
alad upon the outer side of the lower jaw. Both seem to be 
purely lateral line nerves. 
The R. mandibularis internus separates from the externus 
at the cephalic border of the ganglion and goes laterad cephalad 
and ventrad immediately to the mucous membrane of the oral 
cavity between the hyoid arch and the quadrate and (farther 
cephalad) the mandible. In the first part of its course it lies 
in the connective tissue between the oral mucous membrane, 
the quadrate and the M. depressor mandibuli, the quadrate 
lying dorsally and the muscle laterally. Farther cephalad it 
passes on the inner side of the suspensorio-hyoid ligament, 
MECKEL’s cartilage and the os articulare on whose mesal side it 
divides, one branch passing through a canal in that bone to 
join the R. circumflexus V,' which at nearly the same level 
passes between the os dentare and MeEckeEL’s cartilage. This 
soon divides on emerging from its canal into the R. submax- 
illaris and R. mandibularis internus V. The remainder of the 
R. mandibularis internus VII runs forward between the mucous. 
membrane and the mandible. At the level of the appearance 
of the M. submaxillaris, it is compressed between that muscle 
and the mucous membrane of the floor of the mouth. The 
portion of the R. mandibularis internus VII which joined the 
trigeminus I was unable to trace. I was unable to trace the 
fibers of the R. mandibularis internus in any of the forms even 
into the neighborhood of taste buds. It is clear, that the R. 
mandibularis internus (alveolaris) in Urodeles has practically 
the same course, the only marked differences being that in 
Necturus, and Proteus, it does not pass through a canal in the 
1T use the name applied to the comparable nerve in the frog, believing 
them homologous. Compare, however, COGHILL, op. cit., pp. 265 and 266. 
