220 THE ANATOMY OF THE HORSE. 



at the forepart of the cranial cavity, gives off from its suiface the olfac- 

 tory nerve fibres. These pass in bundles through the foramina of the 

 cribriform plate and enter the nasal fossa, where they are distributed as 

 a network in the olfactory m\icous membrane. As the fibres leave the 

 cranium, they cany with them prolongations from the membranes of 

 the brain ; and they are remarkable among cerebro-spinal nerves in 

 being destitute of the white substance of Scwhann. 



Spheno-palatine Nerve. This nerve, already seen at the back of the 

 orbit as a branch of the superior maxillary division of the 5th (page 214), 

 enters the nasal fossa by the spheno-palatine foramen, and divides into 

 an outer and an inner branch for the nasal mucous membrane, on 

 which it confers common sensibility. 



The Nasal Branch of the Ophthalmic Nerve (page 238) is another 

 nerve of common sensation. Entering the upper extremity of the nasal 

 fossa, through a foramen in the cribriform plate, it ramifies in the 

 mucous membrane on both sides of the fossa. 



Vessels. The mucous membrane of the nasal fossa is richly supplied 

 with blood by the spheno-palatine artery and the nasal branch of the 

 ophthalmic arteiy (pages 213 and 238), satellites of the two preceding 

 nerves. The veins form beneath the mucous membrane a rich plexus 

 which is drained principally by the spheno-palatine vein. 



