74 VETERINARY STATE BOARD 



cells in the upper third of the nasal fossas. Function : preside over 

 the sense of smell. 



Give the origin and the distribution of the optic nerve. 



Origin : From the commissure and optic tracts which arise from 

 the thalamus and corpora quadrigemina. 

 Distribution : To the retina. 



Describe the third pair of cranial nerves, the oculomotor. 



Originates superficially from the crura near the interpedun- 

 cular fissure, deeply, from the anterior border of the pons. Passes 

 through the smallest suprasphenoidal foramen of the orbit. Dis- 

 tributed to all the muscles of the eye except the external rectus, the 

 great oblique and part of the posterior rectus, and by the ophthalmic 

 ganglion to the iris. 



Give the origin and the distribution of the fourth pair of cranial nerves. 

 The patheticum originates in the band of Reil, behind the cor- 

 pora quadrigemina and, deeply, from the interior of the isthmus. 

 It is distributed to the great oblique muscle of the eye. 



Describe the fifth pair of cranial nerves, the trifacial. 



This nerve originates by two roots, motor and sensory, in the 

 pons varolii. On the sensory branch, in the region of the occipito- 

 sphenotemporal hiatus, is a large ganglion, the Gasserian, which 

 gives rise to the three branches of the nerve, viz., the superior 

 maxillary, the inferior maxillary and the ophthalmic. The motor 

 root passes along, but outside of, the ganglion and unites with the 

 fibres of the inferior maxillary branch. So, although the fifth pair 

 is called a mixed nerve, in reality only the inferior maxillary branch 

 is conrposed of sensory and motor fibres. 



The branches emerge from the cranial cavity as follows: the 

 first branch (ophthalmic) passes through the smallest of the large 

 suprasphenoidal foramina to the orbit and is distributed to the skin 

 of the forehead and eyelids, lachrymal gland and nasal fossa. The 

 second, superior maxillary, passes through the foramen rotundum 

 to the orbit and along the infra-orbital canal, where it ends in small 

 branches to the face and upper lip. It sends branches to the eyeball, 

 palate, nose and teeth of the upper jaw. The third, inferior maxil- 

 lary, passes through the foramen ovale to the temporomaxillary 

 articulation and then passes downward to enter the inferior dental 

 canal; it supplies the muscles of mastication and the teeth of the 

 lower jaw. 



On the course of the fifth pair of nerves, the following ganglia 



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