GENERAL VIEW OF THE SKULL. 



39 



arch, which is semi-elliptical in form, and marks the entrance to 

 a large cavity above called the nasal chamber ; this cavity is, in 

 the fresh state, divided into right and left compartments or fossa' 

 by a cartilaginous septum. 



Between the posterior molars and the palatine arch are the 

 two palatine foramina. Behind, and 

 bounded by the palatine arch, are the 

 entrances to the nasal chamber, right 

 and left, called the posterior nares, 

 and the slender median bone stretch- 

 ing from behind forwards in the cavity 

 is the vomer ; it indicates the division 

 of the chamber into right and left 

 fosssd. Continuous with the vomer 

 we find an irregular column of bono 

 reaching to the back of the skull ; 

 this column consists of three j^ieces, 

 the pre-sphenoid anteriorly, then the 

 basi-sphenoid, and lastly the basi- 

 occipital bone. These bones arc 

 respectively parts of the sphenoid and 

 occipital bones, and they, together 

 with the vomer, are regarded as the 

 centra of the cranial vertehrcu ; and 

 the ossified suture between the last 

 two bones is usually marked by a 

 roughened ridge. 



On the posterior edges of the pala- 

 tine arch are two small sharp projec- 

 tions, the ends of the pterygoid bones, 

 and behind them the rough palatine 

 ridges, the posterior edges of which 

 are formed by the pterygoid processes 

 of the sphenoid bone ; outside the 

 base of each of these processes we 

 have the posterior aperture of the 

 siibsphenoidal or pterygoid foramen, which gives passage to 

 an important artery. There are two large, rounded, and may be 

 roughened promineiices, the alveolar tuberosities, immediately 

 behind the last molar teeth, and between them and the palatine 

 ridges and pterygoid bones are the smooth staphyline grooves. 



Inferior aspect of Horse's skull, the 

 mandible being removed. Above the 

 line A is the posterior regiou or liase, 

 between A and B the middle, and 

 below C the anterior or nasal region. 

 a, Occipital condyle ; b, Foramen mag- 

 num ; c, Styloid process ; d, Temporal 

 articular surface ; e, Basi-occipital, 

 and/, IJasi-splienoid bones ; cj. Petrosal 

 bone ; 7), Ali-sphenoid boue ; i. Tem- 

 poral bone ; h. Condyloid foi-amen ; k' 

 Condyloid notch ; I, Foramen lacerum 

 basis cranii ; vi , Pterygoid foramen ; 

 n, Palatine suture ; o. Palatine fora- 

 men ; p, Molar teeth ; <i. Incisive 

 opening ; r, Foramen incisivuin. 



