CRANIAL NERVES 



545 



Name. 



1. Olfactory, s* 



2. Optic. s. 



Origin. 



Front of fore- 

 brain. 

 Optic thalami. 



Distribution. 



3. Oculomotor or Floor of mid 



ciliary, in.* brain 



4. Pathetic or 



trochlear, m. 



From pos- 

 terior part of 

 optic lobes. 



5. Trigeminal. 



s. and m. 



6. Abducens. w. 



7. Facial. 



s. and m. 



8. Auditory. s. 



9. Glossopharyn- 



geal. 



s. and m. 

 10. Vagus or Pneu- 

 mogastric. 



s. and m. 



Medulla ob- 

 longata. 



Olfactory organ. 

 Eye. 



All the muscles of 

 the eye but two. 



Superior oblique 

 muscle of the eye. 



(i) Ophthalmic to 

 snout. s. 



(2) Maxillary to 

 the upper jaw, etc.s. 



(3) Mandibular to 

 lower jaw, lips, etc. 



m. and s. 



External rectus of 

 eye. 



(i) Hyoidean and 

 spiracular. 



(2) Palatine. 



(3) Buccal and 

 facial. 



Ear. 



First gill arch. 



Posterior gills and 

 arches, lungs, heart, 

 gut, and body 

 generally. 



Notes. 



Quite per se. 



. Quite per se. 



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. 



Gasseriaii ganglion 

 at roots. 



The ophthalmicus 

 profundus, often in- 

 cluded with 5, is pro- 

 bably the dorsal com- 

 ponent of 3. 



Perhaps belongs to 

 7, as a ventral branch. 



Ganglia at 

 roots of 7^and 8. 



the 



Apparently a com- 

 plex, including the 

 elements of four or 

 five nerves. 



In higher Vertebrates there are two others, the spinal accessory (11) and the hypo- 

 glossal (12). 



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 has lost most of its sensory 

 branches, and become chiefly motor. 



* The letter s. is a contraction for sensory or afferent, i.e. transmitting impulses 

 from a sensitive area to the centre ; and m. is a contraction for motor or efferent, i.e. 

 transmitting impulses from the centre to muscles and glands. 



There is much uncertainty in regard to the morphological value of 

 the various cranial nerves, but the follovi^ing conclusions may be 

 stated : — 



(i) 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 

 dorsals, which have a more superficial course and include numerous 



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