102 ORGANS OF SUPPORT^ 



musk-deers, where there are canine teeth, and they are 

 wanting in the females of most ruminantia. The orbits are 

 thrown to the sides of the head by the great development 

 of the frontal bones, which are chiefly occupied with air ; 

 from the large sinuses, they communicate with the tem- 

 poral fosse, but have a complete osseous margin by the 

 extension downwards of the malar process of the frontal to 

 the jugal bone. The lachrymal bone extends downwards 

 over the face, to assist in lengthening the head, the alveolar 

 portions of the jaws are deep, for the long malar teeth, and 

 the broad nasal bones cover a large and long nasal cavity. 

 The turbinated bones are of great size, the malar bone is 

 prolonged over the face, the zygomatic arch is very small, 

 and has the coracoid process of the lower jaw extended to a 

 great height through it, which limits the lateral motion of 

 the lower jaw during mastication. The long slender inter- 

 maxillary bones are generally destitute of teeth, the malar 

 teeth with oblique crowns have the layers of enamel directed 

 longitudinally, the motion of the lower jaw being from side 

 to side. The lower jaw being much narrower than the 

 upper, the lateral motion is required to bring the teeth into 

 apposition for mastication, and the glenoid and condyloid 

 surfaces are therefore flat, to admit of this extensive motion. 

 The cervical vertebrae (Fig. 55. c,) are of a lengthened form, 

 with short processes, to give length and mobility to the 

 neck, and the spinous processes of the dorsal vertebrae (c?,) 

 are long, for the attachment and support of the long neck 

 and often weighty head. The ribs extend over a great part 

 of the trunk (z 9 ) and the transverse processes of the lumbar 

 vertebrae are of great length, to assist in the support of the 

 heavy abdominal viscera. The pelvis (p,) is lengthened 

 backwards, the sacro-iliac articulation (n,) is more or less 

 oblique, to give greater elasticity to the movements of the 

 legs, and the coccygeal vertebrae (o,) are numerous and 

 highly moveable, the tail being generally employed as a 

 hand, to brush away insects from the surface of the body. The 

 anterior part of the thorax, destitute of clavicles, is so com- 

 pressed that several of the first pairs of ribs are almost straight, 

 by which the arms are approximated and brought more nearly 

 under the centre of gravity of the heavy trunk, from which 

 they would have been thrown out and endangered by the 



