1 66 EQUINE ANATOMY. 



upward and outward, the inferior oblique downward and inward, 

 and the retractor oculi, as its name implies. 



Nerves. The sixth nerve supplies the external rectus and 

 retractor oculi, the fourth the superior oblique, and the third the 

 remainder. 



APPENDAGES OF THE EYE. 



The Eyebrows are small and furnished with long hairs. 



The Eyelids are two in number, superior and inferior. The 

 angles of continuation are called the external and internal canthi. 

 They are covered with skin externally and conjunctiva internally, 

 with long hairs and orifices of Meibomian glands on the edges. 

 Their framework is made up of muscles and tarsal cartilages, two 

 thin plates, the upper being the larger. 



The Meibomian Glands pour out a sebaceous matter to 

 lubricate the lids. They lie between the cartilage and conjunc- 

 tiva and are tubular in character. 



The Conjunctiva is a mucous membrane, thin and vascular, 

 lining the lids and covering the anterior part of the globe. 



The Membrana Nictitans is an accessory lid lying at the 

 nasal angle of the orbit, composed of elastic cartilage. It serves 

 to remove foreign bodies from the eye. 



The Caruncle is a small, red elevation at the inner canthus, 

 which directs the tears toward the puncta. 



The Tear Apparatus consists of the lachrymal gland, canalic- 

 uli, lachrymal sac and nasal duct. 



The lachrymal gland is conglomerate, lying under the roof of 

 the orbit, and secretes the tears, which empty on the inner sur- 

 face of the upper lid. 



The excess of tears enter the canaliculi, two small canals in the 

 upper and inner lids, which run from openings on the lids, the 

 puncta to the lachrymal sac, a dilatation in the lachrymal fossa. 

 This sac forms the beginning of the nasal duct, which runs down 

 in the lachrymal bone as a membranous canal, to end near the 

 nostril on its inner side. 



The Ocular Sheath is a firm, fibrous membrane binding the 

 structures of the orbit together. 



Blood Supply. 



Ophthalmic from internal maxillary, giving off ciliary, arteria 

 centralis retina, supra-orbital, and lachrymal to the gland. 



