THE RABBIT. 



73 



is well developed it is called the scapula. This is triangular 

 in shape, and has on its outer surface a long ridge ending 

 in a curious umbrella-handle-shaped free termination, the 

 acromion and metacromion processes (fig. 37). At its ventral 

 end it bears an articular surface for the limb, the glenoid 

 surface. At the anterior side of this is a little curved 

 projection which in a young animal is seen to be a separate 

 bone : this is the coracoid or postero-ventral bone, or all that 

 is left of it. The antero-ventral bone or clavicle (collar-bone 

 of man) is also greatly reduced in the rabbit : it may be 

 found in the course of a liga- 

 ment that runs from the scapula 

 to the sternum, as a small rod- 

 like bone with a nodule of 

 cartilage at either end. 



11. The Fore-limb in the 



rabbit is chiefly used for bur- 

 rowing and running; to a less 

 extent for grasping food ; its 

 range of motion is, therefore, 

 much more limited than that 

 of man's arm. If the student, 

 seated before a table, will place 

 his hands side by side on the 

 table, palms downwards, he will 

 have them in what is called 

 the prone position. From this 

 position it is quite easy for him to turn them into the 

 supine position, i.e. palms upwards, without moving his 

 upper arm at all. This is because the second segment of 

 his arm, thanks to its containing two bones, is capable 

 of considerable rotation. But in the rabbit the limb is 

 fixed in the prone position and cannot be supinated : 

 this is an advantage in burrowing. 



The first bone is called the humerus (fig. 38) : the most 

 noteworthy feature in it is the deep olecranon fossa at the 

 distal end of its extensor surface a deep hollow, making 

 an actual perforation of the bone at one point : this is 

 characteristic of mammalia, and the reason for it wo shall 



Fig. 88. HUMERUS. 



