374 NERVOUS SYSTEM. 



ceived standard of nomenclature. The only justifiable departure 

 from this rule, is where something new has been actually disco- 

 vered, a necessity of course then exists for giving a new name 

 as it would riot do to take the appropriated name of any thing 

 else. 



The Olfactory Nerve or First Pair (JVervus Olfactorius, Par 

 Primiim,) is situated on the^under surface of the anterior lobes 

 of the brain, near the fissure that separates the hemispheres. It 

 goes forwards from its root, and also converges gradually to- 

 wards its fellow, so as to reach the cribriform plate of the eth- 

 moid bone, through the perforations of which it passes out. 

 In its course, it is lodged in a small furrow of the cerebrum, by 

 which pressure upon it is prevented. 



This nerve arises by three medullary fasciculi, or roots, from 

 the basis of the brain at the corpus striatum, in the fissure of 

 Sylvius, where the anterior and middle lobes join each other: 

 these roots are from eight to twelve lines on the outer side of 

 the infundibuium. The roots are placed, in regard to each other 

 diverging; one is within, another in the middle, and the third 

 external. The externalroot is the longest, and arises from the 

 extreme posterior margin of the anterior lobe by its last convo- 

 lution; being connected with the middle lobe, and also with the 

 anterior commissure. It has a curved course from without in- 

 wards, the concavity of which is forwards, and the convexity 

 backwards. The internal root is concealed by the chiasm of 

 the optic nerves, and arises from the adjacent surface of the 

 anterior lobe. The middle root comes from the posterior mar- 

 gin of the anterior lobe by the cribriform surface, which is be- 

 tween the other two roots. These origins, emanating from 

 the cortical substance, unite to form a single prismatic cord, 

 which increases in size as it advances forwards, and consists 

 of medullary and cineritious longitudinal fibres mixed to- 

 gether. 



The anterior extremity of the olfactory nerve is swollen out 

 into what is called the Bulb,* (Bulbus,) and sends from its un- 



* Many anatomists consider this as a ganglion, from its extreme development 

 in the sheep, bullock, horse, &c., and, therefore, call it the Olfactory Ganglion. 

 Rolando. Solly on the Brain. 



