368 THE NERVE SYSTEM 



convey impulses to and from the centres in the brain 

 to the structures of the body. They are divided into 

 cranial nerves, which do not pass through the spinal 

 cord, but leave the brain direct from various locations ; 

 and spinal nerves, which derive their nerve fibers 

 from the spinal cord and pass out of the spinal canal 

 by way of the foramen between the vertebra. 



The Cranial Nerves. The cranial nerves consist of 

 twelve pairs, as follows : 



I. Olfactory (fila). 

 II. Optic. 



III. Oculomotor. 



IV. Trochlear. 

 V. Trigeminal. 



VI. Abducent. 

 VII. Facial. 



Nervus intermedius. 

 VIII. Acoustic. 



1. Cochlearis. 



2. Vestibularis. 

 IX. Glossopharyngeal. 



X. Vagus. 

 XI. Spinal accessory. 



1. Accessory to vagus. 



2. Spinal part. 

 XII. Hypoglossal. 



These nerves have each a superficial and a deep 

 origin. The former corresponds to its point of attach- 

 ment at the surface of the brain; the latter to certain 

 nuclei or collections of nerve cells in the structure of 

 the brain. The superficial origin only will be men- 

 tioned. 



THE OLFACTORY NERVES (FIRST). The olfactory 

 nerves or fila are the special nerves of the sense of 

 smell. Twenty in number on each side. They are 

 distributed to the olfactory region in the upper part 



