51 THE BONES, 



3. The styloid bone, or great Tiyoideal branch, is long, thin, flattened 

 on both sides, and directed obliquely from above to below, and before to 

 behind ; it presents two faces, two borders, and two extremities. The faces 

 an external and internal are marked by some few imprints. The 

 anterior border is sharp and slightly concave in its upper third. The 

 posterior border is thicker, and is divided into two portions : a superior or 

 horizontal, which is very short, and an inferior or vertical, much more 

 extensive. The angle they form at their point of junction presents a 

 salient, and more or less roughened, tuberosity. The superior extremity is 

 united to the hyoideal prolongation of the temporal bone by means of a 

 cylindrical fibro-cartilage. By its inferior extremity, the styloid bone is 

 united either to the styloid nucleus or the styloid cornu, forming a sharp 

 elbow directed forwards. The styloid bone, developed from a single 

 centre of ossification, is almost entirely formed of compact tissue. 



OF THE HEAD IN GENERAL. 



From the union of all the bones which constitute the cranium and face 

 results a quadrangular pyramid, whose summit is inverted, which it is 

 necessary to study as a whole. We will pass in review, successively, its 

 four faces, its base, and its summit. 



Anterior Face. The anterior aspect of the head has the parietal, frontal, 

 and nasal bones for its base. Superiorly, it inclines backwards and offers, 

 on each side of the parietal ridges, two bulging surfaces which form part 

 of the temporal fossae. For the remainder of its extent, it presents a plane 

 surface which forms the base of the forehead and the middle portion of 

 the face. Wide above, this surface gradually tapers to the extremity of the 

 nasal spine. In well-formed animals, it is as straight and wide as possible. 



Posterior Face. This face, which is extremely irregular, presents : 

 above, the basilar process, the lacerated foramina, and the base of the 

 tuberous portion of the temporal bones ; then the intramaxillary space, 

 and, at the bottom of this, the body of the sphenoid bone, vidian fissure, 

 superior orifice of the subsphenoidal canal, sphenoidal process, palatine 

 ridges, pterygoid bones, guttural openings of the nasal cavities separated 

 from one another by the posterior border of the vomer, roof of the palate, 

 incisive openings, and the incisive foramen. 



Lateral Faces. These exhibit : behind, the external face of the maxillary 

 branches ; before, a surface more or less convex, though sometimes hollow 

 in old animals, presenting at its middle the inferior orifice of the maxillo- 

 dental canal, arid forming the base of the lateral parts of the face ; above, 

 the zygomatic ridge and arch, the orbit, and the temporal fossa. These 

 two cavities, in the formation of which many bones participate, have been 

 .hitherto merely indicated ; this is the place for giving them a more detailed 

 description. 



The orbit or orbital cavity is irregularly circular in outline, and 

 circumscribed by the orbital process of the frontal bone, the lachrymal and 

 malar bones, and the summit of the zygomatic process. At the bottom, 

 which shows the maxillary and orbital hiatus, it is confounded, in the 

 skeleton, with the temporal fossa. 1 It lodges the globe of the eye and 

 the muscles which move it. Some organs, accessory to the visual apparatus, 



* A fibrous membrane, the ocular sheath, isolates it from the temporal fossa in the 

 majority of mammiferous animals. Only in Man and the quadrumana has the orbital 

 cavity complete bony walls. 



