62 



THE CAT. 



[chap. hi. 



noticed. The condyles (c) are elongated convex prominences placed 

 somewhat obliquely, converging forwards. The inner border of 

 each is rough, for the attachment of one of the " check " ligaments. 

 In front of each condyle is a perforation, the anterior condyloid 

 foramen (1), which allows the hypoglossal nerve 

 to pass out from the brain, while a canal (the 

 hinder opening of which is a little within the 

 margin of the foramen magnum) traverses the ex- 

 occipital on its inner aspect. External to each 

 condyle is an expanded process of bone called the 

 par-occipital 2))'occsf^ (j)), the front surface of which 

 is applied to the posterior surface of the auditory 

 bulla. The root of the par-occipital process forms 

 the hinder boundary of the aperture of the skull 

 through which the jugular vein comes out, which 

 aperture is called the foramen lacerum jugulare, or 

 foramen lacerum posterius. 



A small triangular bone, the interparietal, in 

 the fully mature cat blends completely with the 

 supra-occipital, but long remains a distinct ossicle. 

 Its base is applied to the mid -part of the superior 

 border of the occipital, while its sharp apex extends 

 forwards between the parictals. It is strongly con- 

 cave within (especially in the transverse direction), 

 but is convex externally. 



If this be counted as a part of the occipital, 

 that bone may be said to articulate above by its superior margin 

 with the parietals, and below this, on each side, with the hinder 

 margin of one of the temporal bones, while each par-occipital 

 process (as before said) applies itself to the hinder end of one of the 

 ordinary bulhi?. The basi- occipital adjoins the hinder part of the 

 bone next in front, namely the sphenoid. 



§ 24. The PARIETAL bone forms, with its fellow of the opposite 

 side, the main part of the roof of the cranium. It would be 

 quadrangular in figure but that its upper, hinder angle is rounded 

 off, and it is strongly convex outwards, and concave within. Its 

 greatest convexity is termed the parietal eminence {e). Above tliis is a 

 curved ridge convex upwards, marking the superior limit of the 

 temporal fossa. Within, the parietal is marked by grooves for 

 blood-vpssels, and its upper margin is traversed by a longitudinal 

 depression, which forms, with the help of the opposite parietal, a 

 longitudinal wide and shallow groove for a blood receptacle called 

 the longitudinal sinus. The two parictals are connected together 

 above by the sagittal suture ; each is connected by the lanibdoidal 

 suture with the interparietal, and with the supra-occipital. The 

 parietal also articulates anteriorly (/) Avith the frontal by the 



Fig. 32. — Inter- 

 parietal Bone. 



A. Outer surface. 



B. Inner .surface. 

 a. Apex which 



liasses forwards 

 between tlie pa- 

 rietal bones. 



h. Hinder margin. 



c. Fossa for recep- 

 tion of part of 

 brain. 



* It has not therefore been reckoned as a distinct bone in the list before given 

 of the bones of the cranium and face. 



