CEREBRO-SPINAL NERVES 



CEREBRO-SPINAL NERVES 

 THE CRANIAL OR ENCEPHALIC NERVES 



If we examine the base of the brain, a number of nerves are seen to 

 come ort' from its surface. They vary in size, as they do also in function, 

 iiiid among them are numbered the nerves of the special senses of smell, 

 sight, taste, and hearing. The cranial nerves are arranged symmetrically on 

 either side of the base of the brain, and for the most part distribute their 

 branches to parts on the side from which they arise. There is a want of 

 agreement in this country between human and veterinary anatomists as 

 to the enumeration of the cranial nerves. By the one they are described 

 as nine, by the other as twelve. AVe need not, however, enter into the 

 pros and cons of this question here, but we give below the numerical 

 designations of each: — 



Name. VeteiiiLary. Hum.an. 



Olfactory Nerves ... ... ... ... 1 1 



Optic Nerves ... ... ... ... 2 2 



Oculo-motor Nerves ... ... 3 3 



Pathetic Nerves ... ... . . ... 4 4 



Trifacial or Lingual Nerves ... ... 5 5 



Abducent Nerves ... ... ... 6 6 



Facial Nerves (Portio dura) 7 "j - 



Auditory Nerves (Portio mollis) h) 



Glosso-pharyngeal Nerves ... ... 9\ 



Pneumogastric or Vagus Nerves ... ... 10[ 8 



Spinal Accessory Nerves ... ... ... 11 J 



Hypoglcssal Nerves ... ... ... 12 9 



First Pair, Olfactory. — The first pair of cranial nerves is the olfiic- 

 tory, a number of fine filaments whose superficial origin is the olfactory 

 bulbs. These bulbous Ijodies are lodged in the ethmoidal fossae of the 

 ethmoid bone, two depressions in front of the cranium, in which a number 

 of minute openings appear and allow of their passage out of the cranium 

 into the sujierior parts of the nostrils, where they are distributed over the 

 schneiderian membrane. 



The olfactory nerves are the first pair of special nerves, whose function 

 is that of receiving the impressions of odours, which they carry to the 

 iirain. 



Second Pair, Optic Nerves. — These nerves are derived from two 

 thick bands which wind round the crura cerebri in their course from 

 their deep origin in the corpora quadrigemina. 



On reaching the inferior surfiice of the cranium, the two optic bands 



