CHAP, in.] SKELETON OF THE HEAD AND TRUNK. 57 



namely, those of hearing, sight, and smell. It may be described 

 as an irregularly and complexly shaped osseous box with an arch, 

 like a flying buttress, on each side, all forming one coherent mass, 

 and with very diversely conditioned arches appended below and not 

 similarly coherent. The first of these inferior arches is the skeleton 

 of the lower jaw, or mandible. The second is the bony framework 

 to which the tongue is attached, the hyoid. Both these inferior 

 arches readily fall away from the rest of the skull when the soft 

 parts are dissolved or otherwise removed. 



Apart from these arches (both inferior and lateral) the skull 

 consists of a spheroidal posterior portion (p), to which is annexed 

 in front an elongated, narrower, and irregularly quadrilateral part, 

 made up of the bones of the face. On each side of the skull (just 

 in front of the spheroidal portion) is a large smooth concave surface 

 (with the concavity outwards), which forms the inner wall of the 

 chamber for the eye, or the orbit ; and the skull is especially narrow 

 from side to side at the hinder and lower part of this region. 



The greater part of the upper region of the skull is smooth and 

 even, and crossed by undulating lines of bony union called suturcs(s). 



When a section is made lengthways (Fig. 49) through the skull, 

 its spheroidal portion is shown to bound a great posterior cavity (for 

 the brain), in front of which is a more solid region the quadrangu- 

 lar part which includes the bones of the nose (Figs. 49 and 50, 

 me, et), and is placed above the mouth and between the eyes. 



The skull consists of two parts : 



(1). The brain-case, skull proper, or cranium. 

 (2). The skeleton of the face. 



Certain conspicuous openings and prominences are found in different 

 regions. 



The projecting portion of the back of the head is termed the 

 occiput, and at its inferior hinder part is a large hole, looking down- 

 wards and backwards, termed the occipital foramen, or foramen 

 magnum (Figs. 29 and 47, fin). On each side of this hole, forming 

 part of its margin, is a rounded projection ; and these projections 

 (Figs. 29 and 47, oc), termed "occipital condyles," articulate with 

 the cup-shaped articular concavities on the anterior side of the atlas 

 vertebra (Fig. 21, B, z). Thus, all but the front part of this foramen 

 (to which the odontoid process is attached by ligament) coincides with 

 the corresponding portion of the ring of the atlas vertebra, and the 

 interior of the skull forms the expanded anterior end of the vertebral 

 neural canal. 



If the skull be turned base upwards (Fig. 29) a large globular 

 prominence (b) will be seen a little in front of and external to each 

 occipital condyle. Each such prominence is called, from its connec- 

 tion with the internal ear, an auditory butta. Between the bullae, 

 the under surface of the cranium extends forward as a narrow flat 

 surface (Fig. 29, bo ancles), bounded laterally by two low, elongated 

 bony plates (pt), external to which is, on either side, the wide cavity 

 of the orbit enclosed by the bony arch just referred to, which arch is 



