434 CRANIAL NERVES. 



above described. The anterior commissure, according to his description, 

 is merely the continuation of this nervous membrane from one lateral 

 cord across the middle line to the other. Moreover, Rolando considers 

 that a thin lamina of pia mater is received between each of the folds 

 from the exterior, while a layer of the grey substance is prolonged 

 between them from within. Cruveilhier is of opinion that each 

 lamella is completely independent of its neighbours, and he believes 

 this statement to be confirmed by pathology, which shows that a 

 single lamella may be injured or atrophied, and at the same time be 

 surrounded by others perfectly sound. 



CRANIAL NERVES. 



There are nine pairs of cranial nerves. Taken in their order from 

 before, backwards, they are as follows : 



1st. Olfactory. 

 2nd. Optic. 



3rd. Motores oculomm. 

 4th. Pathetici (trochleares). 

 5th. Trifacial (trigemini). 

 6th. Abducentes. 

 7th \ Facial (portio dura), 

 ' ( Auditory (portio mollis). 



C Glosso-pharyngeal, 

 8th. < Pneumogastric (vagus, par vagum). 



( Spinal accessory. 

 9th. Hypoglossal (lingual). 



Functionally or physiologically the cranial nerves admit of division 

 into three groups, namely, nerves of special sense, nerves of motion, 

 and compound nerves, that is, nerves which contain fibres both of 

 sensation and motion. The nerves belonging to these groups are the 

 following : 



Cist. Olfactory. 

 Special sense . . . < 2nd. Optic. 



(_7th. Auditory. 



/ 3rd. Motores oculorum. 



I 4th. Pathetici. 



Motion J 6th. Abducentes. 



j 7th. Facial. 

 V9th. Hypoglossal. 

 f 5th. Trifacial. 



r J 8th. Glosso-pharvngeal. 



Compound . . . . ^ Pneumogastric 



(, Spinal accessory. 



