TEMPORAL BONE. 49 



runs along the median line; and near the inner surface of the orbital 

 plate is a longitudinal notch, the incisura sj^henoidalis, into which 

 the orbital portion of the sphenoid bone is received. The anterior 

 concavities form the frontal sinus, which is separated from its 

 fellow by a prominence termed the nasal spine, on the posterior 

 part of which is a rounded surface, which joins the crista galli 

 process of the ethmoid bone. 



The ijosterior boixler is divided into two parts, both of which 

 are denticulated, the superior part articulating with the parietal, 

 while the inferior or descending part is overlapped by the 

 squamosal bone. The anterior border is pointed at the frontal 

 suture, and articulates partly with the nasal and partly with the 

 lachrymal bone. The interned border is straight and triangular, 

 the widest part being at the septum ; it joins its fellow. The 

 outer and inferior border is very irregular, and articulates with 

 the sphenoid and lachrymal bones. The frontal bone articulates 

 with nine bones : — its fellow, the parietal, squamosal, sphenoid, 

 ethmoid, lachrymal, nasal, palatine, and superior maxillary bones. 



TEMPORAL BONE. 



(Fig. 12. 4, 5.) 



Situated at the side of the cranium, the temporal bone is divided, 

 in the horse, into two distinct pieces, named the squamoscd or 

 squamous temporal, and the petrosal or petrous temporal bones. 



The Squamosal Bone (Fig. 10. III.) is irregularly oval, 

 flattened, and slightly curved, with a strong process arching out- 

 wards and forwards. It has an external and an internal, or 

 cerebral surface, and a circumferent border. 



The external surface is rather convex, presenting numerous 

 small foramina, which lead into the parieto-temporal conduit, a 

 cavity between it and the parietal bone. Projecting outwards 

 and forwards from its middle is a long, ai'ched process, the 

 zygomatic, which unites with a similar process of the malar bone 

 to form the zygomatic arch, on which the frontal arch abuts 

 superiorly. Posterior to this abutment is a broad convex surface, 

 which forms the inferior part of the temporal fossa; and pro- 

 jecting upwards from the postero- external part of the fossa is the 

 sharp zygomatic spine. The shallow transverse concavity on the 

 inferior face of the zygomatic process is the glenoid cavity, with 

 which the condyle of the lower jaw articulates; and continuous 



