34 OUTLINES OF EQUINE ANATOMY. 



two processes. The body is externally convex, affording 

 attachment to levator labii superioris. Its internal surface 

 lies in contact with its fellow by a broad roughened surface, 

 and the two bones here together form foramen incisiorum, 

 running from the roof of the mouth at its extreme ante- 

 rior part. The anterior attachment of septum nasi extends 

 on the bone as far as this foramen. The inferior margin 

 of the body presents on each side three alveolar cavities, 

 into which the incisors lit. These are conical depressions, 

 separated from each other by thin bony plates ; thus the 

 two central incisors have between them two bony laminae. 

 Behind the convex alveolar line is a smooth portion of 

 the lower margin of the bone, and behind this is a ^portion 

 of the alveolar cavity for the tush, which is completed by the 

 superior maxillary bone. From the supero-posterior part 

 of the body an elongated process passes obliquely upwards 

 and backwards. It^ superior margin Y\m^ irom the upper 

 portion of the symjjhysis, first outwards, then upwards, as 

 far as os naris. It is rounded, to its external surface 

 dilator naris inferior is attached, and it winds round 

 towards the false nostril. Its posterior margin, inferiorly 

 by squamous suture, superiorly by schindylesis, is in con- 

 nection with the superior maxillary bone. The up^er 

 margin is united to the anterior part of the roughed por- 

 tion of the outer margin of the os nasi. The inner surface 

 forms the anterior margin of the lateral boundary of the 

 nasal chamber. The inferior surface of the body of this 

 bone slopes obliquely upwards and backwards, and centrally 

 terminates in a thin process, the p>alatine, running back- 

 wards towards the palatine process of the superior maxillary 

 bone. It is flattened from above downwards ; its extreme 

 postero-superior parts in some cases is in apposition with 

 the anterior extremity of the vomer ; it forms the inner 

 boundary of a space, incisive opening, which is generally 

 filled with cartilaginous matter continuous superiorly with 

 septum nasi, embedded in which is the organ of Jacobson. 

 Os maxillare superius is a large bone, with its fellow 

 forming a very considerable portion of the face. It assists 

 in forming several cavities, and completely forms one of 

 the facial sinuses, the inferior maxillary. These sinuses, 

 however, are only found markedly developed in the adult. 

 It presents two surfaces and four margins. The superior 

 margin is irregular, being in apposition with the outer 



