THE ENTIKE SKULL 479 



the large area for the rectus capitis posticus minor. The line of 

 attachment for the capsular ligament joins the upper ends of the 

 condyles above the 'margin of the foramen magnum. 



INTERIOR OF THE SKULL. 



In order properly to examine the interior of the skull, the student 

 will need three specimens, prepared as follows : 



(1.) A skull should be sawn in two along a horizontal longitudinal 

 plane which passes, in front, through the frontal postorbital processes, 

 and, behind, through the occipital bone above the foramen magnum 

 (Fig. 390). 



(2.) A second skull should be bisected along a vertical longi- 

 tudinal plane a little to one side of the median vertical plane. The 

 half of the skull which exhibits the mesethmoid should be retained 

 (Fig. 391). 



(3.) From the other half, the ethmoid, the maxillo-turbmal, and 

 the median walls of the frontal and sphenoidal sinuses should be 

 broken away, and a cast, in fusible metal, made of the cranial and 

 nasal cavities (Fig. 392). 



The skull encloses ten cavities. Two of these are large, unpaired, 

 and lie in the median line ; eight are small and arranged in pairs, four 

 on each side. 



Of the two median cavities the posterior and larger is the cranial 

 cavity, containing the brain, and the anterior and smaller is the nasal 

 cavity, partially subdivided into two chambers containing the compli- 

 cated scrolls of the ethmoid and largely devoted to the sense of smell. 



Of the paired cavities four small ones are connected with the back 

 part of the nasal cavity, one on each side above, the frontal sinuses, 

 and one on each side below, the sphenoidal sinuses. They are con- 

 tained in the frontals and the sphenoid, but do not communicate with 

 the cranial cavity. When the facial part of the skull is removed the 

 large anterior openings of these sinuses are seen above and below on 

 the front aspect of the cranium proper (Fig. 200). The remaining 

 four cavities of the skull are on each side in its lower posterior portion. 

 They also are formed by the bones of the cranium, and are not con- 

 nected with the cranial cavity, except by small canals for the passage 

 of nerves and vessels. Of these four cavities two are the labyrinths, 

 or cavities of the internal ear, and are small and hidden away on each 



