64 THE HUMAN BODY 



a slender curved bone attached dorsally to the body and transverse 

 process of a vertebra in the manner already mentioned, and con- 

 tinued ventrally by a costal cartilage (Fig. 18). In the case of the 

 anterior seven pairs, the costal cartilages are attached directly to 

 the sides of the breast-bone; the next three cartilages are each at- 

 tached to the cartilage of the preceding rib, while the cartilages of 

 the eleventh and twelfth ribs are quite unattached ventrally, so 

 these are called the free or floating ribs. The convexity of each 

 curved rib is turned outwards so as to give roundness to the sides 

 of the chest and increase its cavity, and each slopes downwards 

 from its vertebral attachment, so that its sternal end is consider- 

 ably lower than its dorsal. 



Sternum. The sternum or breast-bone (Fig. 28 and Fig. 14) 

 is wider from side to side than dorsoventrally. It consists in the 

 adult of three pieces, and seen from the ventral side has somewhat 

 the form of a dagger. At the upper end are notches for the articu- 

 lations of the collar-bones (Fig. 28, Id), and along each side notches 

 for the articulations of the anterior costal cartilages (Fig. 28, Ic, 



1-7). 



The Appendicular Skeleton. This consists of the shoulder- 

 girdle and the bones of the fore limbs, and the pelvic girdle and the 

 bones of the posterior limbs. The two supporting girdles in their 

 natural position with reference to the trunk skeleton are repre- 

 sented in Fig. 30. 



The Shoulder-girdle, or Pectoral Arch. This is made up, on 

 each side, of the scapula or shoulder-blade, and the clavicle or collar- 

 bone. 



The scapula (S, Fig. 30) is a flattish triangular bone which can 

 readily be felt on the back of the thorax. It is not directly articu- 

 lated to the axial skeleton, but lies embedded in the muscles and 

 other parts outside the ribs on each side of the vertebral column. 

 From its dorsal side arises a crest to which the outer end of the 

 collar-bone is fixed, and on its outer edge is a shallow cup into 

 which the top of the arm-bone fits: this hollow is known as the 

 glenoid fossa. 



The collar-bone (C, Fig. 30) is cylindrical and attached at its 

 inner end to the sternum as shown in the figure, fitting into the 

 notch represented at Id in Fig. 28. 



The Pelvic Girdle (Fig. 30). This consists of a large bone, the 



