794 



PHYLUM CHORDATA : CLASS MAMMALIA 



cess. The scapula is usually strong and the clavicle is 

 as a rule present in Mammals which grasp or climb or 

 burrow. 



The fore-limb consists of an upper arm or humerus, a 

 forearm of two bones — the radius and the ulna, a wrist or 



Fig. 476. — Scapula of a rabbit. — From a Specimen. 



SC, Blade of the scapula ; SP., spine of the scapula on which 

 muscles are inserted ; S.SC, cartilaginous trace of a supra- 

 scapula ; A. P., acromion process at the end of the spine ; 

 M.P., an offshoot, the metacromion process; G.C., the 

 glenoid cavity, with which the head of the humerus 

 articulates ; C.P., the coracoid process, which forms 

 part of the glenoid cavity. In the embryo it is a separate 

 bone. 



carpus, five palm-bones or metacarpals, and five digits with 

 joints or phalanges. 



The head of the humerus works in the glenoid cavity formed by the 

 scapula. 



When the arm of a mammal is directed outwards at right angles to 

 the body, with the palm vertical and the thumb uppermost, the thumb 

 and the radius are in a preaxial position, the little finger and the ulna 



