304 THE RABBIT 



5. The Caudal Region. 



The caudal vertebrae, from fifteen to eighteen in number, are gradually 

 reduced in size and lose their processes towards the end of the tail. The first 

 two or three are fused with the sacral vertebrae. 



C. The Ribs and Sternum. 



The ribs (along with the thoracic vertebrae) form the supporting framework 

 of the walls of the thorax. There are twelve or thirteen pairs of ribs, each 

 having the form of a curved rod articulating with the thoracic vertebrae, and 

 consisting (typically) of an upper bony vertebral portion and a lower cartilagin- 

 ous sternal portion. The first seven pairs of ribs are connected with the sternum 

 or breast-bone by their cartilaginous sternal portions. The sternal portions of 

 the eighth and ninth pairs of ribs are connected with the ribs in fi-ont of them. 

 The last three pairs have no sternal portions. The ends of the ribs which 

 articulate with the vertebral column have each a knob known as the head or 

 capitulum. The first nine pairs have an additional facet, the tubercle, for 

 articulation with the transverse process of the vertebra. 



The sternum or breast-bone is transversely segmented. The first segment, 

 the manubrium, is keeled ; the last or seventh segment, the xiphisternum, ends 

 in a flattened cartilage. 



II. The Appendicular Skeleton. 



1. The Pectoral or Shoulder Girdle. 



Remove the pectoral girdle and fore-limb. The girdle is attached, outside 

 the ribs, by muscles and ligaments only. Note the following parts : — 



(a) The scapula or shoulder-blade, a flattened triangular bone, with its apex 



directed downwards and forwards and enlarged and hollowed out 

 ventrally to form the glenoid cavity for the articulation of the head 

 of the humerus. 



(b) The cartilaginous suprascapula, on the short upper border of the scapula. 



(c) The prominent ridge or spine, along the outer surface of the scapula, 



ending in the acromion process, which is prolonged backwards as 



the long metacromion process. 

 {d) The short and hook-like coracoid process, at the apex of the glenoid 



cavity. 

 (e) The clavicle, a small and slender, curved bone, lying in the ligament 



between the acromium and the sternum. 

 Make a sketch of the scapula. 



2. The Fore-limb. 



Carefully clean the left fore-limb, and note the following parts : — 



{a) The humerus (upper arm), a long bone. Its head articulates in the 

 glenoid cavity of the scapula. In front of the head is the bicipital 

 groove for the tendon of the biceps muscle ; this groove is bounded by 

 two roughened projections, the lesser tuberosity on the inner side, and 

 the greater tuberosity on the outer side. At the lower end is a piiUey- 

 like trochlea, which articulates with the radius and ulna to form the 

 elbow-joint. Above the trochlea are two supra-trochlear fossae, the 



