276 THE NERVOUS SYSTEM 



It has been supposed that the cerebellum is in some way 

 connected with the generative function, and this much is 

 probably true, though the evidence submitted is not suffi- 

 cient to warrant the assumption that the cerebellum is the 

 seat of the sexual instinct. 



THE CRANIAL NERVES. 



The cranial nerves, twelve in number on each side, take 

 their origin from some part of the encephalon, pierce the 

 dura mater and leave the skull by various openings. They 

 have been numbered from before backward in the order in 

 which they pass through the dura mater. Their names, 

 indicating something of their function, and corresponding to 

 their numbers, are as follows : 



I. Olfactory. 

 II. Optic. 



III. Motor Oculi Communis. 



IV. Patheticus (Trochlearis). 

 V. Trifacial (Trigeminus). 



VI. Abducens. 

 VII. Facial. 

 VIII. Auditory. 

 IX. Glosso-pharyngeal. 



X. Pneumogastric (Vagus). 

 XI. Spinal Accessory. 

 XII. Hypoglossal. 



The point at which one of these nerves can be seen to issue 

 from the brain tissue is the apparent origin, while the gray 

 nucleus, or nuclei, to which the fibers can be traced in the 

 brain substance is the deep origin. 



First Nerve (Olfactory). 



Origin. This is a nerve of special sense. Its apparent 

 origin is by three roots. The internal root issues from the 



