84. 



THE BONES OF THE HEAD. 



absent on one or both sides. Externally to the condyle is a projecting portion of 

 bone known as the jugular process ; this lies over the transverse process of the atlas, 

 and is continuous behind with the tabular part, while in front it has a free excavated 

 margin, the jugular notch, which contributes, with a notch in the temporal bone, to 

 form the jugular foramen. Its extremity presents a small irregular surface, which 

 articulates with the jugular facet of the petrous part of the temporal bone by 

 synchondrosis, passing into osseous union at about twenty-five years of age. The 

 upper surface of the jugular process is marked by a deep groove for the lateral sinus 



SUP. TEMP. LINE 



INF. TEMP. LINE 



TEMP. SURF. 



Fig. 34. RIGHT PARIETAL BONE : EXTERNAL SURFACE. (Drawn by D. Gunn.) f 



leading to the jugular notch, and here is seen the inner opening of the posterior 

 condylar foramen ; the under surface is rough for the insertion of the rectus capitis 

 lateralis muscle. 



The basilar process projects forwards and upwards in the middle of the base 

 of the skull. It increases in thickness and diminishes in breadth towards its 

 extremity. On the inferior surface in the mid-line is a small elevation, phanjngeal 

 tubercle, for the attachment of the fibrous raphe of the pharynx, and on each side of 

 this are impressions for the rectus capitis anticus major and minor muscles. Its 

 superior surface presents a central smooth hollow, the basilar groove, which supports 

 the medulla oblongata, and close to each lateral margin a shallow groove for the 

 inferior petrosal sinus. 



Varieties. The portion of the bone above the superior curved lines, which represents the 

 interparietal bone of lower animals, is in rare cases separated from the rest by a suture 

 running transversely from one lateral angle to the other ; partial separation by lateral fissures 

 is often met with (p. 73). The area between the superior and highest curved lines is 

 occasionally very prominent, constituting the torus occipitalis transrersus. In some bones 

 there is a groove along the internal occipital crest for the occipital sinus. The anterior 

 condylar foramen is not unfrequently double. An intra jugular process is often seen in the 

 form of a small projection at the fore part of the jugular notch ; occasionally it is longer, and 

 meets the petrous portion of the temporal bone (p. 71). A projection from the under aspect 



