THE NERVOUS SYSTEM OF THE FROG. 
along its length: it then ends in branches 
which run along the jaw, some forwards 
and some backwards, supplying the skin of 
the upper lip, the lower eyelid and other 
neighbouring parts. 
(. The ramus mandibularis: runs parallel to 
and behind the ramus maxillaris as far as 
the outer border of the eyeball, giving 
branches to the temporal and pterygoid 
muscles : it then turns backwards, outwards, 
and downwards, and passing across the inner 
side of the upper jaw, reaches the outer 
surface of the mandible just behind the 
insertion of the temporal muscle: it then 
runs forward along the outer side of the 
lower jaw to the chin, supplying the lower 
lip and the muscles of the floor of the mouth. 
6. The abducens: a very slender nerve which arises from 
the ventral surface of the medulla close to the median 
line, and a short way behind the pituitary body. It 
passes either through, or in very close contact with, the 
Gasserian ganglion, and entering the orbit supplies the 
retractor bulbi and the rectus externus muscles. 
The nerve is too small to be dissected satisfactorily in the frog. 
7. The facial nerve: arises from the side of the medulla 
immediately behind the trigeminal nerve, and passes 
forward to the skull wall where it is very closely con- 
nected with the Gasserian ganglion. It passes through 
the skull wall immediately behind and in close company 
with the trigeminal nerve, and divides at once into its 
two main branches. 
i. The ramus palatinus; runs forward in the floor 
of the orbit a short distance from the side wall 
of the skull, and immediately beneath the 
mucous membrane of the floor of the mouth. 
Near the anterior end of the orbit it divides 
into two branches, one of which runs outwards 
and anastomoses with the ramus maxillaris of 
the trigeminal nerve, while the other runs for- 
