76 



THE SKELETON OF THE HORSE 



temporal artery emerges. The inlet of the orbital cavity (Aditus orbitse) is cir- 

 cumscribed by a complete bony ring, which is nearly circular. Its infraorbital 

 margin (Margo infraorbitalis) is smooth and rounded; the supraorbital margin 

 (Margo supraorbitahs) is rough and irregularly notched. During life the cavity is 

 completed by the periorbita, a conical fibrous membrane, the apex of which is at- 

 tached around the optic foramen. Ventral to the orbital cavity is the pterygo- 

 palatine fossa. Its wall is formed by the pterygoid process, the perpendicular 

 part of the palate bone, and the tuber maxillare. Its deep anterior recess contains 

 three foramina. The upper one, the maxillary foramen, is the entrance to the in- 



Exiernal occipital pro- 

 tuberance 



Occipital condyle 

 — '■ Paramastoid process 



— Condyloid fossa 



— Mastoid process 

 Bulla ossea 



Postglenoid process 



■ Glenoid cavity 



Temporal condyle 

 Zygomatic process 

 ~ Infratemporal fossa 

 Zygomatic process of 

 malar 



Pterygo-palati7ie fossa 

 ^\ — Maxillary recess 



Maxillary tuberosity 

 Facial crest 

 Hamulus of pterygoid 

 Vomer 



Palatine bone {hori- 

 zontal part) 

 Ant. palatine foramen 



Palatine groove 



Palatine process of 

 maxilla 



Fig. 49. — Line Drawing of Posterior Half of Base of Skull of Horse, Without Mandible. (Key to Fig. 50.) 

 A, Basilar part of occipital; B, body of sphenoid; C, temporal wing of sphenoid; D, squamous temporal bone; 

 i?, petrous temporal bone; F, orbital part of frontal bone, i, Incisura carotica; ^, incisura ovalis; 5, incisura spinosa; 

 4, external orifice of temporal canal; >'>, osseous auditory or Eustachian tube; 6, petro-tympanic fissure; 7, external 

 acoustic process; 5, hyoid process ; 5, pterygoid groove; i(3, supraorbital process. 



Nuchal crest 



Dorsal border of 



for. magnum 



Foramen magnum 



Hypoglossal foramen 



For. lacerum posterius 



Stylomastoid fora^nen 



Hyoid process 

 Muscular process - 

 For. lacerum anterius -- 

 Basilar tubercles - 



Alar canal • 



Pterygoid process 

 of sphenoid 

 Pterygoid bone - 



Vomer (ato) _ 

 Pterygoid process of 



palatine bone 

 Palatine bone (per- „ 



pendicular part) 

 Alveolar tuberosity 



Posterior nares ■ 

 Last molar tooth - 



fraorbital canal, which transmits the infraorbital nerve and vessels. The spheno- 

 palatine foramen perforates the medial wall of the recess and transmits vessels and 

 nerves of like name to the nasal cavity. The lower foramen, the posterior palatine, 

 transmits the palatine artery and nerve to the palatine canal. The upper part of 

 the fossa is smooth, and is crossed by the internal maxillary artery and the maxillary 

 nerve. The lower part is chiefly roughened for the attachment of the lateral 

 pterygoid muscle, but is crossed in front by a smooth groove in which the palatine 

 ^'ein lies. In its extreme posterior part is the small opening of the pterygoid 

 canal. 



The preorbital or maxillary region is formed chiefly by the maxilla, but also by 



