66 



THE BONES. 



shows the continuation of the 

 foramen. These three faces 



Fig. 38. 



POSTERIOR ASPECT OF HORSE'S 

 SKULL. 



, Occipital tuberosity ; 2, fora- 

 men magnum ; 3, 3, occipital 

 condyles ; 4, 4, styloid pro- 

 cesses ; 5, 5, petrous bone ; 6, 

 basilar process ; 7, pterygoid 

 fissure of the sphenoid bone ; 8, 

 foramen lacerum ; 9, 9, supra- 

 condyloid, or anterior mastoid 

 process ; 10, 10, articular emi- 

 nence, or temporal condyle ; 11, 

 body of sphenoid bone ; 12, ptery- 

 goid process ; 13, ethmoid bone ; 

 14, temporal bone and sphenoidal 

 sutuie; 15, lachrymal bone; 16, 

 vomer; 17, malar bone; 18, 

 maxillary tuberosity ; 19, pos- 

 terior nares, or guttural opening 

 of the nose ; 20, palatine bone ; 

 21, palatine styloid process ; 22, 

 palato-maxillary foramen; 23, 

 palatine process of superior 

 maxillary bone, with suture ; 24, 

 ditto of premaxillary bone; 25, 

 premaxillary bone ; 26, upper 

 incisor teeth ; 27, point of junc- 

 tion of the premaxillary with 

 the supermaxillary bone ; 28, up- 

 per molar teeth (young mouth). 



palatine groove, which terminates in the incisive 

 are separated by as many borders : two internah 

 hmitiug the corresponding face before and be- 

 hind ; and an external, separating the labial from 

 the buccal face. The latter only merits notice. 

 It is very thick, and is divided into two parts : 

 an inferior, which describes a curved line, con- 

 cavity upwards, and is excavated by three alveoli 

 for the reception of the incisor teeth ; another, the 

 superior, is straight, vertical, and somewhat sharp, 

 and forms part of the dental interspace. It is 

 limited above, near the base of the external process, 

 by a cavity for the formation of the alveolus of 

 the canine tooth. 



Processes. — These are distinguished as external 

 and intei'iial. The first, the longest and strongest, 

 is flattened on both sides ; its external face is 

 smooth, and continued with that of the thick por- 

 tion of the bone ; its internal face is covered by 

 the mucous membrane of the nose ; the anterior 

 border is smooth and rounded ; the posterior, 

 denticulated to respond to the supermaxillary bone, 

 is in contact with the external border of the base ; 

 its summit is thin, and is insinuated between the 

 latter and the nasal bone. The internal {ox palatine) 

 process, the smallest, is flattened from before to 

 behind, and forms a very thin tongue of bone, sepa- 

 rated from the other portions by a narrow and very 

 deep notch, named the incisive opening or cleft. Its 

 inferior face constitutes a small portion of the floor 

 of the nasal fossae ; the posterior, continuous with 

 the same face of the principal mass of the bone, 

 forms part of the palatine roof ; its external border 

 circumscribes, inwardly, the incisive opening ; the 

 internal is united by dentated suture with the 

 opposite bone. 



Structure and development. — It is a spongy 

 bone, developed from a single nucleus. 



Differential Characters in the Premaxillary Bone 

 OF OTHER Animals. 



A. Ox, Sheep, Goat (Fig. 37).— Tlie iuferior or prin- 

 cipal portion of this bone is flattened befure and behind, 

 and deprived of alveoli in its external border; neither is there 

 any incdsive foramen. It is rarely consolidated with the 

 adjacent bones, and is never, in the smaller Ruminants 

 (Sheep and Goat), articulated with the nasal bone by the 

 summit of the external process. 



B. Camel. — By its form, tlie premaxillary bone much 

 resembles that of the smaller Ruminants. Its base is 

 not so wide, but it is thicker than in the Ox. This base is 

 rugged in its lower surface, and excavated by an alveolar 



