.38 OSTEOLOGY. 



the position of the late suture. One of the principal sutures of 

 the skull is the longitudinal, which extends in the median line 

 from the poll to the nasal peak, and marks the division of the 

 skull into two lateral halves. 



In shape the skull resembles a quadrangular pyramid, and 

 contains various cavities or chambers. Supposing it to be placed 

 in the horizontal position resting on the lower jaw, we can more 

 easily give a general description of the most important external 

 features if we divide it into the following regions : — Superior, 

 Inferior, Lateral, Anterior, and Posterior. 



The Superior region is a surface formed by three pairs of bones, 

 called the parietal, frontal, and nasal, each bone being joined to 

 its fellow by a part of the longitudinal suture. The parietal 

 bones are the hindermost of the three, and are convex, forming 

 part of the roof of the cranium or brain cavity, while the frontal 

 or middle pair are flatter, and very broad above the level of 

 the orbits, the region of the forehead. The nasal bones together 

 form a semi-cylinder, and gradually diminish in breadth anteriorly, 

 finally forming the projecting nasal peak. The prominent trans- 

 verse ridge bounding this region posteriorly is the occipital crest. 



The Inferior region presents a very irregular surface, bounded 

 below by the inferior maxilla or lower jaw, a bone whose two 

 segments are firmly united anteriorly, but diverge backwards 

 somewhat in the form of a letter V, each terminating superiorly 

 in a convex articular surface, the maxillary condyle, before which 

 is the prominent coronoid process, the lever of the lower jaw. 

 The diverging parts or rami of the jaw include a space, appro- 

 priately called the maxillary space. We find in the united or 

 anterior portion of this bone the inferior incisor and, in the male, 

 the canine teeth, and in the rami the inferior molars or grinders; 

 the space between the molar and front teeth is called the 

 diastema or interdental space, and is always large in herbivorous 

 animals. 



If we remove the inferior maxilla, we notice the following 

 objects : — Anteriorly the premaxilla, bearing the upper incisor 

 and partly the canine teeth, and just behind the incisors, in the 

 median line, a small round aperture, the foramen incisivum, while 

 the interdental space and molar teeth are similar to those in the 

 lower jaw. The flattened surface extending from the incisors 

 backwards between the molars is the bony palate, formed chiefly 

 by the superior maxilla, and bounded posteriorly by the 'palatine 



