OLFACTORY NERVES 



745 



FIRST OR OLFACTORY NERVES 



The olfactory nerves are twenty to thirty in number on each side. They rise 

 from the lower surfaces of the olfactory bulbs, and are grey filaments devciid of 

 wliite sheaths. They pass in two rows, inner and outer, througii the foramina in 

 the cribriform plate of the ethmoid. Entering the olfactory mucous memlirane 

 they anastomose together and afterwards break up into filaments. The filaments 

 of the outt^" group are distributed over the upper and middle turbinal bones in the 

 upper fifth of the outer wall of the nasal cavity, and those of the inner group 

 over a similar extent of the U})})er part of the septum. 



The olfactory nerve-fibres are processes of special olfactory cells in tbc upper 

 ])arts of the nasal mucous memln'ane. They terminate in tlie olfactory bull) in 

 ramifications which are interwoven with the dendrites of the mitral cells of the 

 bulb forming with them the olfactory glomeruli. From the mitral cells fil)res pass 



Fig. 442. — Xekves of the Nasal Cavity. 



XA SA L OLFA CTOR Y 



FRONTAL SiN US XER\'E NERVE 



OLFAf'TORY SERVE 

 TO SUPERIOR TUR- 

 BINATE HOSE 



^—— SPHENOIDAL SINUS 



VIDIAN SERVE 



MECKEL'S 



GANGLION 

 DESCENDINU 



PALATINE 



ORIFICE OF EUSTACHIAN 

 TUBE 



NASAL BRANUllES 



POSTERIOR 



PALATINE 

 ANTERIOR 



PALATINE 

 MIDDLE PA LA TINE 



backwards into the olfactorv tract. Thest^ may bt- classified int<^ two groups, 

 namely: — (a) Fibres which enter the cortex of the tract; and {b) fibres which pass 

 throtigh the white matter to other ])arts of the l)rain without becoming connected 

 to the cortex of the tract, (a) From the cortex of the tract some fibres pass rid 

 the external Avhite root to the cortex of the temporal lobe. Others enter the ante- 

 rior coimnissure, and })roceed to the cereliral cortex of the op])osite side, (h^ Of 

 the fibres which pass directly through the tract, some ])ass by the external white 

 root to the temporal lobe; others pass as a slender tract into the under border of 

 the internal capsule, and so reach the front of the optic thalamus fObersteiner). 

 A ctunmissural bundle of fibres, which passes from one olfactorv tract to its fellow 

 of the opposite side, rid the anterior commissure, is also descriljed. 



As they pass through the foramina in the cribriform ]ilate, the olfactory nerve- 

 fibres are invested In- sheaths derived from tlie dura mater. 



