180 THE ANATOMY OF THE HORSE. 



beneath the lachrymal gland, it is succeeded by a thin flat tendon, 

 which in the lid is placed beneath the palpebral tendon, and joins 

 the tarsal 'cartilage. 



Action. — To open the eye by raising the upper lid. In this move- 

 ment the muscle plays over the eyeball like a rope over a pulley. 

 The lower lid, it is to be observed, has no analogous muscle, because, 

 in the first place, it is raised but slightly under the action of the 

 orbicularis, and, secondly, because its own weight and elasticity are 

 sufficient to depress it. 



Vessels. The arteries of the eyelids are derived from the supra- 

 orbital and lachrymal arteries, and from the orbital branch of the 

 superior, dental artery. 



The Supra-Orbital Artery will be found emerging from the orbit by 

 the supra-orbital foramen. It is a branch of the ophthalmic artery. 



The Lachrymal Artery is also a branch of the ophthalmic, and is 

 distributed mainly to the gland of the same name, but it sends some 

 twigs to the upper eyelid. 



The Orbital Branch of the Stiperior Dental Artery creeps over the 

 lower part of the rim of the orbit, and descends to anastomose with 

 the submaxillary artery. It gives some twigs to the lower eyelid. 



Nerves. The sensory nerves of the eyelids are derived from the 

 supra-orbital and palpebrb-nasal branches of the ophthalmic division 

 of the 5th cranial nerve, and from the 'orbital branch of the superior 

 maxillary division of the 5th. The supra-orbital nerve emerges by the 

 foramen of the same name, and is distributed to the upper eyelid, and to 

 skin around its point of exit. The palpebronasal nerve sends a branch 

 to supply the lower lid and the structures at the inner canthus. The 

 orbital branch of the superior maxillary division of the 5th nerve is 

 distributed in the neighbourhood of the outer canthus. The motor 

 nerve to the orbicularis comes from the 7th, which crosses internal to 

 the nasal canthus. The motor nerve to the levator palpebrse comes 

 from the 3rd, but cannot be reached at present. 



THE FACE. 



The Nostrils, or the Inferior or Anterior Nares; Some points in 

 connection with these may conveniently be noticed before the student 

 proceeds to dissect the face. The nostril is the entrance to the nasal 

 chamber or fossa — the first segment of the respiratory passages. It is a 

 large, somewhat oval opening, bounded laterally by the alee, or wings, 

 of the nostril. The ala3 meet above and below, forming the commissures, 

 the lower of which is wide and rounded, while the upper is acute. The 

 outer ala is concave in the whole of its extent ; but the inner ala, while 

 concave below, forms a convex projection close to the upper commissure. 



