CLASSIFICATION OF THE CRANIAL NERVES 



495 



Nerve of mastication, or motor root of the fifth pair. 



Facial, sometimes called the nerve of expression. (Seventh pair.) 



Spinal accessory. (Eleventh pair.) 



Sublingual. (Twelfth pair.) 



Nerves of General Sensibility 



Trifacial, or large root of the fifth pair. 



A portion of the glosso-pharyngeal. (Ninth pair.) 



Pneumogastric. (Tenth pair.) 



In the above arrangement the nerves are classified according to their 

 properties at their roots. In their 

 course, some of these nerves be- 

 come mixed and their branches 

 are both motor and sensory, such 

 as the pneumogastric and the 

 inferior maxillary division of 

 the trifacial. 



The nerves of special sense 

 have- little or no general sensi- 

 bility ; and with the exception 

 of the gustatory nerves, they do 

 not present ganglia on their 

 roots, in this, also, differing from 

 the ordinary sensory nerves. 

 They are capable of conveying 

 to the nerve-centres only certain 

 peculiar impressions, such as 

 odors, for the olfactory nerves, 

 light, for the optic nerves, and 

 sound, for the auditory nerves. 

 The proper transmission of 



Fig. 117. Roots of the cranial nerves (Hirschfeld). 



I, olfactory; II, optic; III, motor oculi communis; 

 these impressions, however, in- IV, patheticus; V, nerve of mastication and trifacial; 



volves the action of accessory 



VI, motor oculi externus ; VII, facial ; VIII, auditory; 

 IX, glosso-pharyngeal ; X, pneumogastric; XI, spinal 

 parts, more Or leSS Complex: accessory; XII, sublingual. The numbers I to 15 



refer to branches that will be described hereafter. 



and the properties of these 



nerves will be considered in connection with the physiology of the spe- 

 cial senses. 



MOTOR OCULI COMMUNIS (THIRD NERVE) 



The third cranial nerve is the most important of the motor nerves 

 distributed to the muscles of the eyeball. Its physiology is readily 

 understood in connection with its distribution, the only point at all obscure 



