62 BONES OF THE HEAD. 



between the maxillary and palate bones. Anteriorly, in the middle 

 line, is the anterior palatine foramen, with the four smaller foramina 

 contained within it ; posteriorly, on each side, at the base of the alveolar 

 arch, is the posterior palatine foramen, and externally and posteriorly 

 to that, the posterior and external small palatine foramina. The palate 

 is surrounded in front and on the sides by the alveolar arch bearing the 

 teeth of the upper jaw. 



The middle division extends back to the front of the foramen magnum. 

 Its central portion has been called the (jutfural fossa. In the middle 

 line is the basilar process of the occipital bone, and in front of that the 

 body of the sphenoid bone, covered anteriorly by the extremity of the 

 vomer. On each side, the petrous portion of the temporal bone reaches 

 as far forwards as the extremity of the basilar process ; and between the 

 petrous and squamous portions of the temporal is the back part of 

 the great wing of the sphenoid bone. Between this division of the base 

 of the skull and the palate are the posterior' nares, separated by the 

 vomer, and bounded aliove l^y the body of the sphenoid bone, below by 

 the horizontal plates of the palate bones, and on the sides by the internal 

 pterygoid processes. Between the pterygoid plates is the pterygoid 

 fossa ; and placed in an oblique line backwards and outwards ft'om this 

 are the foramen ovale, foramen spinosum, and processus spinosus; 

 while behind and parallel to these is a groove for the Eustachian iulye, 

 formed by the margins of the sphenoid bone and pars petrosa, leading 

 into the Eustachian orifice, and in a line with the fissure of Glaser. 

 Between the apex of the pars petrosa, the basilar process, and the 

 sphenoid bone, is the foramen lacerum medium, on the external wall of 

 which opens the carotid canal, and on the anterior the Vidian canal ; 

 it is closed inferiorly by a plate of cartilage, and its area is crossed by 

 the internal carotid artery and the Vidian nerve. Behind the pars 

 petrosa, and bounded posteriorly by the jugular fossa of the occipital 

 bone, is the foramen jui/ulare, ov foramen lacerum jjoster ins : it is divided 

 into a large rounded part situated externally and posteriorly, bounded 

 in front by the jugular fossa of the temporal bone, and occupied by the 

 jugular vein ; and a narrow angular part situated anteriorly and in- 

 ternally, bounded by a portion of the pars petrosa distinct ft'om the 

 jugular fossa, and transmitting the eighth pair of cranial nerves. 

 These two parts are sometimes separated by a spiculum of bone. In 

 front of this is the carotid foramen, on its outside is the stylo-mastoid 

 foramen and styloid process, and internal to it is the anterior condyloid 

 foramen. 



The posterior division presents on eacli side of the foramen magnum, 

 ft'om within outwards, the occipital condyle, the rough surface for the 

 rectus capitis lateralis muscle, the occipital groove of the temporal bone, 

 the digastric fossa^ and the mastoid process. Behind the foramen mag- 

 jaum is the tabular part of the occipital bone, with its ridges and 

 muscular impressions. 



THE INTERIOR OF THE CRANIUM. 



The walls of the cranium consist of two layers of compact bony sub- 

 stance, the outer and inner tables, and an intervening cancellated 

 substance, called diploe. Tlie inner or vitreous table, has a smooth, 

 close-grained, shining appearance, is hard and brittle, and presents 



