CRANIUM 



185 



malar or cheek-hone below. This is the zygomatic process, on the under 

 surface of which will be seen a concavity for the reception of the condyle 

 of the lower jaw, the two to- 

 gether forming the inferior 

 maxillary articulation or joint. 



Petrous Temporal. Two 



small hard irregular bones, but 

 of considerable importance ow- 

 ing to their having within them 

 the special organs of hearing. 

 They are interposed between 

 the occipital bones above, and 

 the parietal and temporal bones 

 below, and assist in forming 

 the lateral walls of the cranium. 

 They are the hardest bones in 

 the skeleton, and from them 

 project several bony processes. 

 One, the external auditory 

 canal, communicates with the 

 middle ear. Another, the sty- 

 loid process, is a long thin piece 

 of bone projecting downward 

 and forward, and behind this is 

 a larger rounded protuberance, 

 the mastoid process, which is 

 hollowed out into a number of 

 small compartments connected 

 with the middle ear. Another 

 small process serves for attach- 

 ment of the tongue bone, and 

 is known as the hyoid process. 



Sphenoid Bone. - - This 



bone assists in forming the base 



of the cranium. It is situated 



immediately below the occipital 



bone, with which it articulates. 



Its middle part or body is 



somewhat thick, and from it proceed upward two flattened portions, 



or wings, and downward two narrower and more slender projections 



(pterygoid processes'). 



Fig. 288. Skull (Posterior Surface! 



1 Foramen Magnum. 2 Styloid Process of Occiput. Ex- 

 ternal Auditory Process. 4 Styloid Process of Petrous Tem- 

 poral Bone. 5 Sphenoid Bone. 6 Pterygoid Process. 'Superior 

 Maxillary Bone. 8 Palatine Bone. 9 Molar Teeth. 10 Pala- 

 tine Process of Superior Maxillary Bone. n Premaxillary Bone. 

 12 Incisor Teeth. 13 Foramen Incissivum. 14 Palato-maxillary 

 Foramen. 15 Vomer. 16 Ethmoid Bone. l7 Temporal Con- 

 dyle. 18 Foramen Lacerum Basis Cranii. 1!) Basilar Process 

 of Occiput. M Petrous Temporal Bone. 21 Occipital Condyle. 



