60 THE CAT. [CHAP. in. 



When the skull is viewed in profile its upper margin is seen 

 to present an even, rounded contour. Its lower margin is 

 nearly straight, with irregular prominences. The line of the 

 occiput (Fig. 46, c to y) inclines somewhat backwards as it 

 ascends. In front, the skull is bounded by the margin of the 

 anterior nares. 



The zygoma arches upwards, backwards, and then downwards to 

 the front of the auditory bulla, enclosing, as well as the orbit, a 

 fossa named "temporal," because a muscle called the "temporal 

 muscle " is there placed. Behind and beneath the hinder end of the 

 zygoma is a noticeable aperture, which is the external bony opening 

 of the ear (ae). A ridge also runs upwards from the malar pro- 

 minence, and forms the anterior margin of the bony orbit. The 

 orbit is bounded behind by an ascending and a descending post- 

 orbital process, which nearly meet. 



The skull is said to be divided into certain regions. Thus we 

 have the base or basilar region, and opposite to it the vertex, or 

 sincipital region ; we have the region of the forehead, or frontal 

 region, and opposite to it that of the back of the head, or occipital 

 region. 



At the side of the head we have, posteriorly and above, the 

 parietal* region (p) ; beneath this, and within the arch of the 

 zygoma, the temporal region. 



The skull is made up of different bones of very different sizes, 

 shapes, and degrees of density, which are variously united together 

 by sutures. 



When the skull is looked at from above, a transverse zigzag line 

 of union is seen to run across behind the forehead ; this is called the 

 coronal suture. Its zigzag appearance is due to the interlocking of 

 little processes which project from the adjacent margins of the bones, 

 the presence of which causes the suture (or line of union) to be 

 what is called " dentated." Running directly backwards and forwards 

 from this, along the middle line of the skull, is another suture at 

 right angles to the former termed sagittal (Fig. 28, s). The sagittal 

 suture ends posteriorly by joining a wide Y-shaped suture with the 

 apex upwards, which is called lamMoidal. 



Turning now to the lower jaw ; this when attached to the skull 

 is seen to fit, by a cylindrical-shaped head, or " condylc" into a 

 depression placed on each side in front of the external auditory 

 opening, the glenoid surface before mentioned. 



The number of bones forming the skull decreases with age, by 

 anchylosis. In its mature condition the skull of the cat consists of 

 the following twenty-seven bones : the occipital, two parietals, two 

 frontals, two temporals, the sphenoid, the presphenoid, the ethmoid 

 which ten bones compose the cranium, or skull proper ; two 

 maxillaries, two premaxillaries, two nasals^two malars, two lachry- 

 mals, two palatines, two turbinals, one vomer, one mandible (in two 



* Because it is here the "parietal bone" is situate. 



