THE SKELETON. 13 



the spinal cord, of which we shall learn hereafter, 

 passes. The vertebrae are divided into three sets. The 

 seven upper ones are in the neck. The next twelve 

 are in the back proper; to these the twelve pairs of 

 ribs are attached. The five lower vertebrae are in 

 the region of the loins. They are very stout, as the 

 figure shows, just as we would expect them to be, 

 since they support a large part of the weight of the 

 body. 



The upper part of the trunk, which con- 



The Chest. 



tains the heart and lungs, is called the 

 chest. The skeleton of the chest is formed behind, 

 as you see, by the middle division of the spinal col- 

 umn; on the sides by the ribs (12, 13), and in front 

 by the sternum (10) or breast-bone. Here, again, we 

 find a wise provision for the protection of life. The 

 breast-bone is not near so hard as most of the other 

 bones. It is consequently more flexible. The ribs 

 are not directly united to the sternum, but are joined 

 to it by cartilages. By these means, a heavy blow 

 on the breast, which otherwise would seriously injure 

 the organs within, is made comparatively harmless. 

 The plate of the skeleton shows that the ribs are 

 not all joined to the breast-bone in front. Seven 

 pairs (12-13) are so joined. These are called true 

 ribs. The remaining five pairs (14-15) are called 

 false ribs. 



The bones of the lower part of the trunk 



The Pelvis. , ., . . .. 



are shaped and joined so as to form a 

 large bowl-shaped cavity. This is called the pelvis. 



