64 



THE SKELETON OF THE HOESE 



The body (Corpus maxillse) presents two surfaces, two borders, and two ex- 

 tremities. The lateral surface (Facies lateraUs) is somewhat concave in front and 

 convex behind.' On its posterior part there is a horizontal ridge, the facial crest 

 (Crista faciahs) ; in a skull of medium size its anterior end is about an inch and a 

 haK (3 to 4 cm.) above the third or fourth cheek tooth, and it is continued behind 

 on the malar bone. About two inches (5 cm.) above and a little in front of the 

 anterior end of the crest is the infraorbital foramen (Foramen infraorbital) ; this 

 is the external opening of the infraorbital canal. 



The medial or nasal surface (Facies nasalis) is concave dorso-ventrally; it 

 forms the greater part of the lateral wall of the nasal cavity. Its upper part is 

 crossed obliquely forward and downward by the shallow lacrimal groove (Sulcus 

 lacrimalis), which contains the naso-lacrimal duct; in the adult the posterior part 

 of the groove is converted into a canal, which is continuous with that on the inner 

 surface of the lacrimal bone. Below the groove is the ventral turbinate crest 

 (Crista turbinata ventralis), to which the ventral turbinate bone is attached. 

 Lower down and parallel with the turbinate crest is the palatine process, which 





Fig. 42. — Right Maxilla of New-born Foal; Medial View. 

 1, Lacrimal groove; 2, ventral turbinate crest; 3, palatine process; 4, maxillary sinus; 5, 5, area of articulation 

 with palatine bone; 0, groove wliich concurs with one on the palatine bone to form the palatine canal; 7, zygomatic 

 process: S, maxillary tuberosity; 9, junction with nasal bone; 10, junction with nasal process of premaxilla. 



projects horizontally like a shelf. Behind this the surface is rough for articulation 

 with the palatine bone; this area is crossed by a groove which concurs with one on 

 the palatine bone in the formation of the palatine canal (Canalis palatinus) . The 

 posterior part of the bone is excavated to form part of the maxillary sinus. 



The dorsal border is irregular and scaly. Its anterior part is grooved and 

 its posterior part beveled for articulation with the nasal process of the premaxilla 

 and the nasal and lacrimal bones. 



The ventral or alveolar border (Processus alveolaris) is in its greater part thick, 

 and presents six large cavities, the dental alveoli, for the cheek teeth. The alveoh 

 are separated by transverse interalveolar septa. There is often a small alveolus 

 for the first premolar ("wolf tooth") close to the first large one. At the bottom 

 of the alveoli there are small openings (Foramina alveolaria) for the passage of 

 vessels and nerves. Further forward the border is narrow and forms part of the 

 interalveolar or interdental space (Margo interalveolaris) . Behind the last alve- 

 olus is a rough area, the alveolar tuberosity (Tuber alveolare). 



The anterior extremity is pointed. It joins the premaxilla, and forms with it 

 the alveolus for the canine tooth. 



- In the young horse the anterior part of the surface is convex over the embedded parts of the 

 teeth. As the hitter are extruded the surface flattens and becomes concave in old subjects. 

 The form of the underlying teeth may be indicated by ridges (Juga alveolaria), and sometimes in 

 young horses there may be defects in the bone over the teeth. 



