226 THE ANATOMY OF THE HORSE. 



cells are connected by their deep ends with the olfactory nerve fibres, 

 while their opposite extremities are insinuated between the columnar 

 cells, and terminate on the surface of the membrane in a few stiff, 

 hair-like processes. In the submucous tissue are numerous tubular 

 glands — the glands of Bowman — which open on the free surface of the 

 membrane. The nasal mucous membrane is continuous with that of 

 Stenson's canal and the organ of Jacobson, the pharynx, and the 

 sinuses of the head. 



The Olfactory (1st Cranial) Nerve. The delicate oval swelling 

 termed the olfactory bulb, which is lodged in the fossa of the same name 

 at the forepart of the cranial cavity, gives off from its surface the 

 olfactory 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 mucous membrane. As the 

 fibres leave the cranium they carry 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 220), 

 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 217) is another 

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

 fossa through a foramin 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 artery (pages 219 and 244), 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. 



