OSTEOLOGY. ' 31 



boundary of foramen lacerum basis cranii. Its superior 

 margin presents externally a squaiaous serrated surface for 

 the squamous temporal bone. In the angle which it forms 

 with the anterior margin is foramen pathetici. The anterior 

 margin, on its inner edge, articulates with the wing of os 

 ethmoides, superiorly presenting the smooth groove which 

 forms foramen lacerum orbitale, more externally foramen 

 rotundum, and on its outer edge a ridge to which peri- 

 orbitale is attached, which terminates inferiorly in an elon- 

 gated process, flattened from side to side. This is the 

 crus of the bone. Its siqjerior margin and anterior extre- 

 mity articulate with os palati ; its inner surface posteriorly 

 with OS pterygoideum, and to its inferior margin are 

 attached masseter internus and pterygoideus. 



OS TEMPORALE SaUAMOSUM (one on each side of 

 the head) is situated at the postero-lateral part of the 

 head, and is so named because its main portion is almost 

 wholly occupied in squamosal connection with the neigh- 

 bouring bones. It is divided into two parts — body and 

 zygoma. The inner surface of the body superiorly along 

 its whole length articulates with the parietal bone. Its 

 anterior margin joins os frontis ; antero- inferiorly it joins 

 the wing of os sphenoides ; postero -inferiorly it presents a 

 deep notch, into which the petrous temporal bone with the 

 external auditory process fits. The posterior margin unites 

 with the petrous temporal bone, and at its extreme posterior 

 part with os occipitis. The central part of the inner surface 

 is smooth, and assists to form the wall of the cranium. The 

 external surface is divided into two almost equal parts by 

 a line running from the postero-superior to the antero- 

 inferior angle, from the anterior part of which the zygoma 

 commences. The space above this line helps to form the 

 temporal fossa, having temporalis attached to it, while 

 superiorly it presents some foramina. The inferior division 

 of this surface is smooth and centrally presents a groove, 

 the inferior opening of the canal between this and the 

 parietal bone. Just in front of this is a small rounded 

 prominence, the mastoid process, to which is attached one 

 of the ligaments of the temporo -maxillary articulation. 

 The zygoma is a large process, which is very thin, flattened 

 from above downwards, running directly outwards at its 

 origin. It is then twisted from below upwards (so that its 

 outer margin becomes superiorly placed), and runs in a 



