72 A COURSE ON ZOOLOGY. 



very easy in articulations of this class, which is the gen- 

 eral method for the long bones. 



The Skeleton. We must limit ourselves to a very brief 

 description of the different regions of the skeleton ; these 

 are three in number, the head, the trunk, and the limbs. 



The bones of the head are classified as those of the 

 skull and those of the face. Those of the skull form a 

 box in which the brain is enclosed. They are eight : the 

 frontal bone of the forehead, the occipital behind, the 

 parietal bones forming the top of the head, the temporals 

 at the sides or temples, the sphenoid below, and the eth- 

 moid in front, and dovetailed into the frontal. There 

 are fourteen bones in the face ; several among which are 

 the palatine and turbinated bones of the nose, the lach- 

 rymals and the vomer are not shown in the accompany- 

 ing figure, either because they are situated in the inte- 

 rior, or because they are too small ; but there are shown 

 the inferior maxillary bone, which forms the lower jaw, 

 the two superior maxillary bones which make up the 

 upper jaw, the two malars or cheek bones, and the nasal 

 bones that form the sides of the nose. 



Among the bones of the head must be mentioned the 

 hyoid bone, a small isolated bone that supports the 

 tongue, and gives rigidity to the upper part of the respi- 

 ratory apparatus. 



The bones of the trunk include the vertebral column, 

 the ribs, the sternum, and the pelvis. 



The middle part of the vertebral column with the ribs 

 and sternum constitute the thorax, a sort of bony cage 

 that encloses the principal organs of circulation and res- 

 piration. The lower portion of the vertebral column, 

 with the iliac bones, which project at the hips, forms a 

 strong bony belt for the support and protection of the 



