208 THE ANATOMY OF THE HORSE. 



the artery here being remarkable in that it is actually within f 

 vein. 



At the inferior end of the sinus the vidian nerve will be found descend 

 ing in the vidian groove to enter the canal of the same name (pag^ 214) 



The Rectus Capitis Antious Major. This muscle was, for the mos 

 part of its extent, exposed in the dissection of the neck, but its tendoi 

 of insertion remains to be examined now (page 155). 



The Eectus Capitis Antious Minor. This small muscle arises iron 

 the lower aspect of the ring of the atlas ; and passing over the occipito- 

 atlantal joint, at the side of the preceding muscle, it becomes insertec 

 into the basilar process of the occipital and the body of the sphenoid ai 

 their point of articulation. 



Action. — To flex the occipito-atlantal joint (to nod the head). 

 , The Rectus Capitis Lateralis. This is another small muscle placec 

 beneath the occipito-atlantal joint. It arises from the atlas, external t( 

 the - origin of the preceding muscle ; and passes to be inserted into th( 

 styloid process of the occipital bone. 



Action. — The same as the preceding muscle. 



THE ORBIT. 



Directions. — With the saw,- cut through the supraorbital prooesi 

 external to the foramen, and through the zygomatic arch at eithe: 

 extremity. The palpebral ligament of the upper lid is to be detachec 

 from the orbital rim, and the tri-radiate piece of bone marked out bi 

 these sections is to be taken away. 



The orbital cavity in the skeleton is not separated from the tempora 

 fossa, but in the living animal a fibrous membrane, continuous with thi 

 periosteum of the bones circumscribing the cavity, completes the orbi 

 on its outer side, and separates it from the temporal fossa. The orbr 

 is thus lined and completed by a fibrous membrane of a conical form 

 termed the ocular sheath. This membrane is composed of fibrous con 

 nective-tissue with some unstriped muscular fibre. 



Contents of the Orbital Cavity. — These are : the eyeball with it 

 muscles, the lachrymal gland, the levator palpebrse, the membrani 

 nictitans, vessels, nerves, and a quantity of fat. For the proper dissec 

 tion of the eyeball, fresh specimens are required, and it is therefor 

 separately described at page 257. The lachrymal gland and th 

 muscles may be dissected on one side, the other being reserved for th 

 display of the vessels and nerves. 



The Lachrymal Gland is the organ which secretes the watery flui 

 that moistens the front of the eye. It is lodged above the eye, beneat 

 the supraorbital process, which is slightly depressed where it covers th 

 gland. In structure it is of the racemose type, resembling the salivar 

 glands, but being looser in texture. Its secretion is discharged by 



