614 ORGANS OF THE SENSES. 



In the roof, the opening leading to the sphenoidal sinus is narrowed, and the 

 apertures in the cribriform plate of the ethmoid completely closed in. 



The arteries of the nasal fossee are the anterior and posterior ethmoidal, from 

 the ophthalmic, which supply the ethmoidal cells, frontal sinuses, and roof of the 

 nose ; the spheno-palatine, from the internal maxillary, which supplies the mucous 

 membrane covering the spongy bones, the meatuses, and septum ; and the alveolar 

 branch of the internal maxillary, which supplies the lining membrane of the 

 antrum. The ramifications of these vessels form a close, plexiform network, 

 beneath and in the substance of the mucous membrane. 



The veins of the nasal fossse form a close network beneath the mucous mem- 

 brane. They pass, some with the veins accompanying the spheno-palatine artery, 

 through the spheno-palatine foramen ; and others, through the alveolar branch, 

 join the facial vein; some accompany the ethmoidal arteries, and terminate in the 

 ophthalmic vein ; and, lastly, a few communicate with the veins in the interior 

 of the skull, through the foramina in the cribriform plate of the ethmoid bone. 



The nerves are the olfactory, 



Fig. 302. Nerves of Septum of Nose. Right Sid.e. t ^ e naga l branch of the ophthal- 

 mic, filaments from the anterior 

 dental branch of the superior 

 maxillary, the Vidian, naso-pala- 

 tine, descending anterior palatine, 

 and spheno-palatine branches of 

 Meckel's ganglion. 



The olfactory, the special nerve 

 of the sense of smell, is distri- 

 buted over the upper third of the 

 septum, and over the surface of 

 the superior and middle spongy 

 bones. 



The nasal branch of the oph- 

 thalmic distributes filaments to 

 the upper and anterior part of 

 the septum, and outer wall of the 

 nasal fossse. 



Filaments from the anterior dental branch of the superior maxillary supply the 

 inferior meatus and inferior turbinated bone. 



The Vidian nerve supplies the upper and back part of the septum, and superior 

 spongy bone; and the upper anterior nasal branches from the spheno-palatine 

 ganglion, have a similar distribution. 



The na so -palatine nerve supplies the middle of the septum. 

 The larger or anterior palatine nerve supplies the middle and lower spongy 

 bones. 



THE EYE. 



The eyeball is contained in the cavity of the orbit. In this situation it is 

 securely protected from injury, whilst its position is such as to insure the most 

 extensive range of sight. It is acted upon by numerous muscles, by which it is 

 capable of being directed to any part, is supplied by vessels and nerves, and is 

 additionally protected in front by several appendages, such as the eyebrow, 

 eyelids, etc. 



The eyeball is spherical in form, having the segment of a smaller and more 

 prominent sphere engrafted upon its anterior part. It is from this circumstance, 

 that the antero-posterior diameter of the eyeball, which measures about an inch, 

 exceeds the transverse diameter by about a line. The segment of the larger 

 sphere, which forms afoout five-sixths of the globe, is opaque, and formed by the 

 sclerotic, the tunic of protection to the eyeball ; the smaller sphere, which forms 

 the remaining sixth, is transparent, and formed by the cornea. The axes of the 



