CHAP. III.] SKELETOX OF THE HEAD AND TRUNK. 79 



afforded, ve find, when the outside of the skull is vieaved in front, 

 (Fig. 30) the following parts : — Below, the maxillae and pre-maxilla) 

 form the alveolar borders. The curved outline of the vertex (/') is 

 formed by the frontals. The two large and conspicuous orbits arc 

 bounded below by the zygomata, from which the malar post-orbital 

 processes (pj) ascend, and approach the descending (;j/') post-orbital 

 processes of the frontals. Between the orbits there is a broadish 

 bony expanse (formed by the frontals, nasals, and maxilla)), except 

 inferiorly where the heart-shaped aperture of the anterior nares is 

 situated — only bounded below by the horizontal processes of the 

 pre-maxillfe {j)"^)- The nasal bones {ii) ascend rather higher than 

 do the nasal processes of the maxillae. On each side of the anterior 

 nasal opening, and just beneath the margin of the lower boundary 

 of the orbit, is the large opening of the infra-orbital canal (2). 



The parts which project furthest outwards are the zygomatic 

 processes of the temporal bones (z). 



At the back of each orbit is seen the convex side-wall of the 

 skull (/) projecting into it, but the foramina which open into the 

 bottom of the orbit are hidden from this point of view. 



On examining the base of the skull (see Fig. 29), we find in 

 front the alveolar margin (describing an acute but truncated angle, 

 with its truncated apex forwards) surrounding the bony palate {m 

 andp), which extends a little further backwards than do the teeth. 

 The anterior end of the bony palate is formed by the pre-maxilla) (^j;>0> 

 between which and the maxillce are the two large anterior palatine 

 foramina. At above the place of junction of the palatine plates of 

 the maxillae with the palatines, there are on each side one or two 

 much smaller foramina, termed the posterior palatine forcujiina (3). 



Behind the palate, we have, in the middle, the meso-pterygoid 

 fossa (^;.s-) (into which the posterior nares open), bounded laterally 

 by the palatines and pterygoids (pt). External to this, is on each 

 side the wide vacant space of the temporal fossa enclosed by the 

 zygoma. 



Behind the meso-pterygoid fossa the basis cranii presents a 

 straight surface of about equal width, formed successively by the 

 under surfaces of the basi-sphenoid (bs) and basi-occipital {ho), and 

 terminated posteriorly by the occipital condyles (oc) and foramen 

 magnum (//«). At the hinder and outer side of each pterygoid 

 bone is the minute pterygoid fossa, external to, and partly hidden by, 

 the hinder part of which is the foramen rotundum (8) ; while the 

 foramen ovale (9) is again just behind, and external to, the foramen 

 rotundum. External to the foramen ovale, and on a line with it, is 

 the glenoid fossa for the lower jaw (^), bounded posteriorly by the 

 post-glenoid process behind, and internal to which is the fissura 

 Glaseri. Behind this again, is the large and swollen auditory 

 bulla {h), at the anterior end of which, immediately behind the 

 foramen ovale, is the anterior aperture of the Eustachian tube (10), 

 and a very small aperture called the foramen lacervni aiiterius, lead- 

 ing into the inside of the cranium. Between the inner hinder part 



