THE FACE. 



47 



anterior edge of the parietal overlies the posterior edge of the frontal. The upper 

 edges of the temporal and sphenoid overlap the lower edges of the frontal and 

 parietal bones. That the temporal region of the skull is distinctly weaker than other 

 regions is due to the thinness of the bones, and the reason that fractures here are 

 exceptionally dangerous is on account of the middle meningeal artery running 

 through a canal in the bone in this region; so that in cases of fracture the artery 

 is torn and hemorrhage occurs above the dura, which causes compression of the 

 brain (Fig. 56). 



The infratemporal crest (crista infratemporalis) or pterygoid ridge sep- 

 arates the temporal region above from the pterygoid region below. It is an important 

 landmark in operating on the Gasserian ganglion. 



A spot two centimetres behind the external angular process and slightly above 

 its level marks the anterior extremity of the fissure of Sylvius. In trephining in the 



Parietal 



Frontal 



Anterior branch, mid- 

 __ _ die meningeal artery 



Glabella 



External angular 



process J"'i'B8m\ If ^L_ Posterior branch 



Infratemporal crest 



Middle meningeal 

 artery (running up 

 on the inside of the 

 skull) 



Zygoma 



Sphenoid 



FIG. 56. Frontal and temporal regions of an adult skull. 



temporal region no diploe is found in the bones, so that extreme care is necessary 

 to avoid wounding the dura mater. The trephine may be placed 4 cm. (ij>4 in. ) 

 behind the external angular process and 4.5 cm. (i ^ in. ) above the zygoma to strike 

 the middle meningeal artery. This will be level with or a little above the highest 

 part of the edge of the orbit. 



Temporal Fascia. This is the dense fascia covering the temporal muscle; it 

 is formed as follows: The pericranium as it comes down from the vault of the skull 

 and reaches the temporal ridge passes under and gives attachment to the temporal 

 muscle. The temporal fascia consists of two distinct sheets of fascia, the superficial 

 one from the superior temporal ridge being attached to the zygoma below and to the 

 malar bone in front; the deeper layer from the inferior temporal ridge covers the 

 temporal muscle, and a short distance above the zygoma divides into two layers, 

 one of which is attached to the outer edge, and the other to its inner edge. The 

 upper or superficial layer of the temporal fascia leaves the bone at the superior tem- 

 poral ridge and is attached below to the top of the zygoma, blending near the bone 

 with the layer beneath. This is a distinct layer though not always readily demon- 

 strable in dissections. Between the layers above the zygoma is some fat and the 

 orbital branch of the middle temporal artery. Anteriorly the temporal fascia is 

 attached to the posterior border of the malar bone and the temporal ridge of the 

 frontal. The temporal fascia is tough and dense and gives attachment by its under 



