122 OUTLINES OF EQUINE ANATOMY. 



the eyelids we may notice that into the inner surface of 

 the tarsal ligament is inserted by a broad tendon the 



Levator palpebrse superioris internus, a muscle which 

 arises from the upper part of the orbital hiatus above 

 rectus superior, and passes within the periorbital membrane 

 to become inserted as described. By playing over the eye- 

 ball it is enabled to raise the eyelid. 



The eyelids receive blood from the ophthalmic artery, 

 from the facial artery, and from the ocular and supra- 

 orbital branches of the internal maxillary artery. Their 

 nerves are derived from the ophthalmic division of the 

 fifth cranial nerve, the supra-orbital branch of which is 

 remarkable as passing to the foramen of that name from 

 the foramen lacerum orbitale externally to the periorbital. 



On the supero-posterior part of the head, on either side 

 of the poll, are situated the structures which compose 

 the external ear. These consist of three cartilages on each 

 side, of the muscles which act upon them, and of the skin 

 which covers one of them extending inwards to line the 

 external ear. Situated nearest to the orbit, resting on the 

 rounded mass which is named the temporal muscle, is an irre- 

 gularly triangular shaped cartilage, which seems to be con- 

 nected to the other cartilages by muscle alone : this is the 

 scutiform cartilag'e. From its external surface the external 

 scuto- auricular es muscles run to theconchial cartilage, and 

 similar muscles may be found attached to its internal sur- 

 face. The conchial cartilage is a portion of membraniform 

 cartilage twisted upon itself in such a manner as superiorly 

 to present a sharp point, externally a wide broad slit, 

 infero-posteriorly a cup-shaped diverticulum, infero- 

 anteriorly a tubular portion along one side of which we 

 see an irregular slit running outwards, filled with fibrous 

 tissue (and from the other side a thin process runs 

 to be attached below to the guttural pouch), which 

 is connected to the external auditory process by a ring- 

 shaped piece of cartilage, the annular cartilage. This 

 cartilage is connected to the external auditory process by 

 yellow elastic tissue, and similarly to the conchial cartilage ; 

 the circular portion of the conchial will fit on the annular, 

 and the annular on the bony process like the joints of a tele- 

 scope, but this action is regulated by muscles which run 

 from one cartilage to the other, which with those running 

 from the scutiform cartilage constitute the intrinsic 



