76 THE SKELETON OF THE HORSE 
temporal artery emerges. The inlet of the orbital cavity (Aditus orbit) 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 supraorbitalis) 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- 
Nuchal crest ------=--—-- = as _ External occipital pro- 
Dorsal border of S tuberance 
for. magnum 
Foramen magnum = -- ~-—--!~-— 
--\-- ------ Occipital condyle 
ae Paramastoid process 
Lf. Condyloid fossa 
Hypoglossal foramen --- 
7 pyr 4 ef pry ee -f_| " 
For. lacerum posterius 3 --- Mastoid process 
Stylomastoid foramen ~~~ — He 
Hyoid process ---+2 
Muscular process - 
For. lacerum anterius ---7* Z BAG Se Glenoid cavity 
Z ‘t\- Temporal condyle 
- Zygomatic process 
Infratemporal fossa 
Zygomatic process of 
malar 
Basilar tubercles - 
Pterygoid process 
of sphenoid 
Plerygoid bone ; 
ie : Pterygo-palatine fossa 
omer (ale) 
Pterygoid process of 
ygoid | ] 
palatine bone = 
Palatine bone (per- - 
pendicular part) 
Alveolar tuberosity - 
Mazxillary recess 
Mavillary tuberosity 
- Facial crest 
Pog Sha Trot Hamulus of pterygoid 
- Vomer 
Palatine bone (hori- 
zontal part) 
Ant. palatine foramen 
Last molar tooth -- 
_~~~ Palatine groove 
— —-- Palatine process of 
maxilla 
Fic. 49.—Line Drawine or Posrertor Hair or 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; 
E, petrous temporal bone; F, orbital part of frontal bone. 1, Incisura carotica; 2, incisura ovalis; 3, incisura spinosa; 
4, external orifice of temporal canal; 5, osseous auditory or Eustachian tube; 6, petro-tympanic fissure; 7, external 
acoustic process; 8, hyoid process; 9, pterygoid groove; 10, supraorbital process. 
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 
vein 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 
