GANGLIA AND NERVES OF SQUALUS 29 
7. RAMUS MANDIBULARIS V 
The r. mandibularis V (figs. 1 and 4, R.Md.V) arises from the 
distal and ventral end of the Gasserian ganglion slightly pos- 
terior to the origin of the r. maxillaris V. Its general course is 
ventral and posterior. This nerve, like the r. maxillaris, is 
large and easily followed at this stage. The first twig given off 
(fig. 1, Mo.1) runs dorsal and mesial to enter the primordium 
of the mandibular muscles. This primordium lies on the mesial 
side of the nerve throughout its whole course and all the motor 
twigs run mesially to enter it, while the sensory twigs have a 
lateral direction. The second twig (fig. 1, S./) runs dorsally and 
laterally to the ectoderm and is general somatic sensory. The 
third twig (fig. 1, R.Com.) runs ventrally and slightly laterally 
and joins the r. maxillaris V, as mentioned above. 
There can be little doubt from the character of the connec- 
‘tion of this anastomosing branch that its fibers run from the 
mandibularis to the maxillaris and that, since the maxillaris 
supplies neither lateral line organs nor muscles, the fibers are 
somatic sensory and destined for the ectoderm, although they 
could not be followed after entering the r. maxillaris. The 
fourth (fig. 1, Mo.2) and fifth (fig. 1, Mo.3) twigs are motor and 
enter the primordium of the mandibular muscles. Their course 
after leaving the main nerve is ventral and mesial. The sixth 
twig (fig. 1, S.2) is sensory and runs to the ectoderm. The 
seventh (fig. 1, Mo.4) is motor and arises nearly opposite the 
sixth. It runs medially and enters the primordium of the 
mandibular muscle. The remaining four twigs (fig. 1, S.3-6) 
seem to be sensory; at leas: they do not enter the primordium 
of the muscle, since they extend beyond the distal extremity 
of the muscle. Neither do they enter the ectoderm but disap- 
pear near the ectoderm and, like the terminal twigs of the r. 
maxillaris, have the appearance of growing nerves. ‘There can- 
not be much doubt that they are somatic sensory fibers. 
