372 A YEAR IN SCIENCE 



3. The lumbar region, or region of the loins, con- 

 sisting of five vertebrae. 



4. The sacral region, consisting of five vertebrae 

 united to form a single bone, the sacrum. 



5. The coccygeal region, four small vertebrae united 

 to form one bone, the coccyx. 



In the diagram locate these regions. To which verte- 

 brae are the ribs attached? Compare the vertebrae 

 in size. "What advantage is this difference in size ? 



Passing through the vertebral column is a canal 

 through which the spinal cord extends and connects 

 with the brain at the base of the skull. 



Ribs and sternum. There are twelve pairs of slen- 

 der curved bones called the ribs. We have already 

 observed their attachment at the back. The first seven 

 pairs are joined at the front by means of cartilage to 

 the breast bone, or sternum; the eighth, ninth, and tenth 

 pairs are attached to the cartilage of the seventh 

 pair; the last two pairs are free or floating ribs. 



Bones of limbs. The upper limbs, or arms, are 

 attached to the shoulder blades and collar bones. The 

 lower limbs, or legs, are attached to the hip bones. The 

 hip bones are large and firmly united to the sacrum. Of 

 what advantage is this? 



The bones of the arms and those of the legs are 

 arranged on the same plan. Locate the following bones 

 in Figure 171. 



Arm humerus Wrist 8 carpals 



Forearm radius and ulna Hand 5 metacarpals 



