Section 7. 

 The Cranial Nerves. 



There are twelve pairs of cranial nerves ; of these two only 

 are required to take part in functions other than those con- 

 nected with the head. This leaves ten pairs, the function of 

 which is wholly connected with the head, either as nerves of 

 special sense, or in a motor or sensory capacity.* 



The special senses for which provision is made are smell, sight, 

 heaving, and taste. Only two of these senses- — viz., smell and 

 sight — have nerves exclusively devoted to their function ; 

 both the senses of hearing and taste are furnished by nerves 

 which perform additional functions : 



The afferent cranial nerves are : 



First, or olfactory. 

 Second, or optic. 

 Eighth, or auditory. 



The efferent nerves are : 



Seventh pair : Motor to the muscles of the face. 

 Eleventh pair : Motor to the muscles of the neck and 



shoulders. 

 Twelfth pair : Motor to the muscles of the tongue. 



Mixed nerves : 



Folirthpairl^ 01 an £ tf nS ° ry t0 thG mUSdeS ° f 

 Sixth pair J the eyeball. 



Fifth pair "| Resemble spinal nerves in consisting of 

 Ninth pair'r a motor and sensory root, with a 

 Tenth pair J ganglion on the latter. 



Afferent Group. 



The nerves of special sense will be dealt with in the chapter 

 devoted to the Senses. 



Efferent Group. 



Seventh Pair, or Facial. — This nerve has been grouped as 

 efferent, but in its course it receives sensory fibres, though at 

 its origin it is exclusively motor. It arises from the medulla 

 behind the pons, at the lateral part of the corpus trapezoides. 

 The deep-seated origin is from the facial nucleus in the medulla. 

 In company with the eighth pair, it passes through the internal 



* The modern system of classifying cranial nerves is described later 

 (P- 5 2 2V 5i4 



