52 ANATOMY OF THE RABBIT 



and distal ends of all dissected muscles while they are fresh in 

 mind. The body should be carefully put away so that it will not 

 dessicate before the other required muscles of the superior limb 

 have been dissected and mastered. 



B. THE FOUR MAJOR FUNCTIONAL GROUPS 



Now that the superior limb has been removed from the trunk, 

 it is clear that its musculature falls into four major functional 

 groups which are comparable in the superior limb of both rabbit 

 and man. (i) Muscles which move the pectoral girdle (Nos. 

 1-5, 6-1 1) . Most of these muscles arise from the axial skeleton, 

 insert on the pectoral girdle and thus attach the scapula and 

 clavicle to the trunk. (2) Muscles which move the arm (Nos. 

 2, 8, 12-20). These muscles arise from the pectoral girdle, 

 or axial skeleton, and insert on the humerus (or antibrachium, 

 e.g., biceps brachii m., 20) and control various movements of the 

 arm at the scapulohumeral articulation (shoulder joint). (3) 

 Muscles which move the antibrachium. This group is sub- 

 divided into those muscles which (a) flex (Nos. 20, 21); (b) 

 extend (No. 22) and (c) rotate (especially in man) the distal 

 half of the forearm and hand and are divided into two antagonis- 

 tic groups in man. (i) Pronators, muscles which turn the radial 

 side of the forearm mediad and the palm caudad, or downward 

 if the forearm is in an extended position, (ii) Supinators which 

 do the opposite, that is, turn the palms craniad or up and the 

 radius laterad, when the Hmb is extended, so that the radius 

 and ulna lie parallel instead of the radius crossing the ulna as in 

 (i). (4) Extensors (Nos. 23-28) and flexors (Nos. 29-32) of the 

 carpals, metacarpals, and digits. 



Further dissection and study will show conclusively that the 

 functions of many individual muscles cannot be readily delim- 

 ited, for they are modified by the action of other muscles. For 

 example, the pectorals (8), latissimus dorsi (2) and basiohumer- 

 ahs (4, 1 2) muscles have their origins on the axial skeleton but 

 are inserted on the humerus instead of the pectoral girdle. 



