490 STRUCTURE OF VERTEBRATA. 
Name. OriGIN. DistTRIBUTION. Noves. 
x. Olfactory. s.* - Front of fore- | Olfactory organ. Quite Jer se. 
rain. 
z. Optic. s Opticthalami.| Eye. Quite fer se. 
3. Oculomotor or 
ciliary. 92.* 
4. Pathetic or 
trochlear. 7, 
. Trigeminal. 
s. and m. 
6. Abducens. mz. 
7. Facial. 
s. and 7. 
8. Auditory. S. 
g. Glossopharyn- 
geal. 
s. and 7. 
Vagus or Pneu- 
mogastric. 
s. and a. 
Io. 
Floor of mid 
brain. 
From pos- 
terior part of 
optic lobes. 
Medulla ob- 
longata. 
All the muscles of 
a eye but two, 
Superiar oblique 
muscle of the eye. 
me Pptinatnne te 
ee Maxillary to 
the upper jaw, etc. s. 
(3) Mandibular to 
lower jaw, lips, etc. 
m. and s. 
External rectus of 
eye. 
(x) Hyoidean and 
spiracular. 1 
(2) Palatine. 
(3) Buccal, facial, 
and auditory. 
Ear. 
First gill arch. 
Posterior gills and 
arches, lungs, heart, 
gut, and body 
generally. 
They cross before 
they enter the brain, 
and generally unite 
at their intersection. 
A ciliary ganglion 
at roots. 
Perhaps belongs to 
5, as a ventral root, 
Gasserian ganglion 
at roots. 
The ophthalmicus 
profundus, often in- 
cluded with 5, is pro- 
bably the dorsal com- 
ponent of 3. 
Perhaps belongs to 
7,asaventral branch. 
Ganglia at the 
roots of 7 and 8. 
Apparently a com- 
plex, including the 
elements of four or 
five nerves. 
In a Vertebrates there are two others, the spinal accessory (11).and the hypo- 
lossal (12: 
S The fourth or pathetic nerve is peculiar among motor nerves in that it appears to 
arise from the extreme dorsal summit of the brain, between the mid- and hind- brain, 
from the region known as the “‘ valve of Vieussens.” In Fishes the seventh nerve is 
mainly a nerve of special sense ; in higher Vertebrates it bas lost most of its sensory 
branches, and become chiefly motor. 
* The letter s. is a contraction for sensory or afferent, z.¢. transmitting impulse 
froma sensitive area to the centre 5 and WM. is a contraction for motor or e! erent, Le. 
transmitting impulses from the centre to the body. 
There is much uncertainty in regard to the morphological value of 
the various cranial nerves, but the following conclusions may be 
stated :— 
(1) Like the spinal nerves, the cranial nerves are primarily seg- 
mental, and there are probably about seven of them,—three pro-otic 
and four metotic. The olfactory and optic nerves are quite by 
themselves and not segmental. 
(2) Like the spinal nerves, the cranial nerves have primarily two 
roots,—a dorsal and a ventral, but the ventral roots do not join the 
