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THE NEEVOUS SYSTEM. 



the olfactory mucous membrane and terminate in the olfactory bulb. The fibres 

 are non-medullated. After their origins from the olfactory cells of the olfactory 

 region on the upper part of the nasal septum and the corresponding part of the 

 lateral wall of the nasal cavity, the nerve fibres form fine plexuses from which the 

 terminal filaments pass through the cribriform plates of the ethmoid on their way 

 to the olfactory bulb. Each filament has a sheath of dura mater. 



Olfactory bulb 



Olfactory trac 



Olfactory tubercl 



Optic n 

 Optic chiasma 



Oculo-motor nerve 

 Trochlear nerve 



Trigeminal nerv 

 Abducens nerv 



Facial ner 

 N. intermediu 

 Acoustic nerv 



Glossopharyngeal nerv 



Vagus nerve 

 Accessory nerve (accessory) 



Accessory nerve (spinal) j 

 Hypoglossal nerve 



Olfactory bulb 



Olfactory tract 



Area parolfactoria 

 Olfactory tubercle 

 Medial stria of olfactory 

 nerve 



Lateral stria 

 Optic chiasma 

 Ant. perforated sub- 

 stance 



e?nporal lobe (cut) 

 ptic tract 

 ulo-motor nerve 



1-Trochlear nerve 

 Stria terminalis 

 Trigeminal nerve 

 -Lat. geniculate body 

 Abducens nerve 

 -Med. geniculate bod) 

 Pulvinar 

 Facial nerve 

 N. intermedius 



, ^Acoustic nerve 



Lateral ventricle 



.Mid. cerebellar peduncli 



Glossopharyngeal nerve 

 Vagus nerve 

 Accessory nerve 

 vAccessory nerve (spina! 



ipital lobe (cut) 



ypoglossal nerve 

 Spinal medulla 

 Vermis of cerebellum (cut) 



FIG. 643. VIEW OP THE INFERIOR SURFACE OF THE BRAIN, 



With the lower portion of the temporal and occipital lobes, and the cerebellum on the left side removed, 

 to show the origins of the cerebral nerves. 



NERVUS OPTICUS. 



The second or optic nerve consists of nerve fibres which spring from the 

 ganglion cells of the retina, and converge to the optic papilla, where they are grouped 

 together to form the optic nerve. The nerve pierces the outer layers of the retina, 

 the chorioid, and the sclera. It pierces the sclera 3 mm. (one-eighth of an inch), 

 to the medial side of the posterior pole of the eyeball, and enters the orbital fat, 

 through which it runs backwards and medially surrounded by the ocular muscles. 

 At the posterior part of the orbit it enters the optic foramen of the sphenoid bone, 

 through which it passes to the middle fossa of the skull, where it ends in the optic 

 chiasma, which lies at the base of the brain, anterior to the interpeduncular area 

 and between the right and the left anterior perforated substance. 



From each of the two postero-lateral angles of the optic chiasma an optic tract 

 sweeps round to the back of the thalamus and to the mid-brain, between the pedun- 

 culus cerebri and the hippocampal gyrus of the corresponding side, and each tract 



