MUSCLES INNEEVATED BY THE FIFTH CEANIAL NERVE. 597 
39 per cent, of the number found in the corresponding nerves 
on the uncut side. This percentage held though the absolute 
numbers were different in the two animals. Thus in animal 
the number of medullated nerve-fibres in the trunk of 
the mylohyoid nerve on the uncut side was 906 ; on the cut 
side it was 335, = 36 per cent. In animal “ B ” the number of 
medullated nerve-fibres in the trunk of the mylohyoid nerve 
on the uncut side was 736, on the cut side it was 280, = 37 per 
cent. 
The persisting medullated nerve-fibres in the muscle 
branches on the cut side were distributed fairly evenly among 
the degenerated ones until near the muscles (fig. 2) ; in the 
nerve-filaments just outside the muscles the persisting and 
degenerated nerve-fibres were largely, though not wholly, 
segregated from one another (fig. 3), and the former tended 
to lie on one side of the filament. 
To ascertain the source of these non-degenerating nerve- 
fibres serial sections were made through the mandibular 
division of the fifth nerve, from the site of operation to the 
point where the various branches had begun to diverge 
from one another. In neither animal are any medullated 
fibres visible in the motor root above the level of the Gasserian 
ganglion — all had undergone degeneration. At the level of 
the Gasserian ganglion, and for a little distance below, medul- 
lated fibres can be seen passing from the sensory into the 
motor root. They lie, for the most part, in the lateral part of the 
motor root, and are more sparsely scattered in its median part 
(fig. 4). 
The ramus lateralis — which innervates the external ptery- 
goid, temporal and masseter muscles — is formed from the 
lateral part of the motor root (figs. 5, 6, 7, 8) ; it also receives, 
from the ramus posterior, those fibres which form its (sensory) 
buccal nerve constituent (fig. 6). The ganglionated afferent 
fibres for the muscle branches of the ramus lateralis thus 
have a simple direct path. 
The paths of the (degenerated) motor and ganglionated 
afferent fibres of the ramus medialis — which innervates the 
