THE FORE-LIMB. 325 



Small cartilaginous nodules occur, one at 

 the outer and two at the inner end of the 

 clavicle. 

 B. The Fore-limb. 



The fore-limb of the rabbit corresponds to the upper limb 

 of man, and may be divided, like this, into arm, forearm, 

 wrist, and hand. The relative positions of these several 

 divisions are considerably altered from the primitive condi- 

 tion, and are best understood by comparing them with the 

 human arm in the following manner : 



Extend your right arm horizontally outwards from the 

 shoulder, with the palm of the hand vertical and the thumb 

 upwards : there may now be distinguished a ventral or flexor 

 surface ; a dorsal or extensor surface ; a preaxial border, 

 along which are the thumb and the radius ; and a postaxial 

 border, along which are the little finger and the ulna. 



Next bend the elbow at right angles, so that the fingers 

 point forwards, and bring the whole arm down to the side, 

 rotating it through 90, so that the preaxial border becomes 

 the outer and the postaxial border the inner one. Now 

 pronate the hand, turning it through 180, so that the thumb 

 is brought to the inner side, and the palm directed down- 

 wards. Place the rabbit's skeleton in front of you, with the 

 vertebral column vertical, the head directed upwards, and 

 the limbs pointing away from you, and the right fore-limb 

 will correspond in position to your own right arm. Note 

 that the preaxial border is on the outer side in the arm, and 

 on the inner side in the hand, while in the forearm the two 

 bones cross each other obliquely. The hand in the rabbit is 

 fixed permanently in the prone position that is, with the 

 palm turned downwards. 



1. The arm contains only a single bone. 



i. The humerus is an elongated bone, articulating 

 by its enlarged proximal head with the glenoid 

 cavity of the scapula, and at its distal end, by 

 the trochlea, with the bones of the forearm. 



At the proximal end of the bone, in front 

 of the head, is the longitudinal bicipital 



