MAN, A MAMMAL 327 



ward ; these form articulations or joints with the neighboring verte- 

 brae. Of the other processes, one projects dorsally and two project 

 laterally ; these give attachment to the muscles of the back. The 

 two vertebrae directly beneath the head are modified so as to permit 

 the skull to rest in the upper one ; this articulates freely with the 

 second vertebra, thus permitting of the nodding and turning move- 

 ments of the head. Besides these individual adaptations, the 

 vertebral column, as a whole, is peculiarly adapted to protect the 

 brain from jar ; this is seen in the double bend of the vertebral 

 column and the pads of cartilage between the individual vertebrae. 

 The whole column of vertebrae joined 

 each to the other supports the weight 

 of the body. The largest vertebrae 

 at the base are joined to the huge 

 pelvic bones for the better support 

 of the body above. That part of the 

 vertebral column of man which bears 

 the ribs is known as the thoracic re- 

 gion. The ribs, twelve in number, are 



long, Curved bones which Combine Ver tebra, showing attachment of 



lightness with strength; joined by ^^' R ^' SP ' 

 elastic cartilage to the sternum in 



front and to the vertebrae behind, they form a wonderful pro- 

 tection to the organs in the thoracic cavity, and yet allow free 

 movement in breathing. 



The Appendages. The parts of the skeleton to which the 

 bones of the anterior and posterior appendages are attached are 

 respectively known as the pectoral girdle (from which hangs the 

 arm) and the pelvic girdle (which joins the leg bones to the 

 axial skeleton). 



The bones of the appendages attached to the pectoral and 

 pelvic girdles are adapted peculiarly to locomotion and sup- 

 port ; for this purpose the bones are long and strong, hinged by 

 very flexible joints. The latter are especially free in the hand 

 to allow for grasping. In the leg, where weight must be supported 

 as well as carried, the bones are bound more firmly to the axial 

 skeleton. The bones of the foot are so arranged that a springy 

 arch is formed which aids greatly in locomotion. 



