12 Leach, The Myology of the Bell-Magpie. [.si^'juiy 



THE MUSCLES OF THE UPPER EXTREMITY (45). 



These are grouped by Shufeldt as follow : — 



I. — The pectoral muscles . . . . . . 3 



II. — Dorsal muscles . . . . . . . . 15 



III. — Tensor-patagii muscles . . . . . . 2 



IV. — Muscles of the brachium . . . . . . 4 



V. — Muscles of the forearm and hand . ." 13 



VI. — Muscles of the hand 8 



45 



/. — The Pectoral Muscles. 



49. The pectoralis major. 



50. The pectoralis secimdiis. 



51. The pectoralis tertitts. 



These muscles are concerned with the raising and lowering of 

 the wing, and are of great importance to flying birds. Strepera, 

 the Australian Raven, Gymnorhina, and Cracticus agree with 

 Shufeldt's description of these muscles in the American Raven. 



49. The pectoralis major [9] [23] is the largest muscle in Strepera. 

 It arises from the whole under surface of sternum (except the 

 part occupied by the pectoralis secitndns and tertius), the keel, and 

 the posterior aspect of the clavicle. It passes upward and forward, 

 covers the biceps, receives the insertion of the dermo-hmneralis 

 (12), and is inserted on the outer side of the humerus on a special 

 crest. 



50. The pectoralis secundus [21] [22fl] arises from the deeper 

 part of the keel and a large part of the sternum between the 

 coracoid and the clavicle. The flattened fibres converge and pass 

 upwards and outwards, becoming a rounded, strong tendon. 

 This passes up through the opening formed by the scapula, coracoid, 

 and clavicle, and, continuing outward and downward, is inserted 

 to the outer side of the radial crest of the humerus, a short 

 distance in front of the insertion of the large breast muscle {49). 

 The pectoralis secundus is concerned with raising the wing. Its 

 purpose is achieved by means of this beautiful pulley arrange- 

 ment, while the centre of gravity is still kept low by having the 

 bulk of the muscle on the ventral side. 



51. The pectoralis tertius [21] is smaller than the preceding 

 muscle. It arises alongside (50) on the sternum and on the outer 

 side of the coracoid bone. Its fibres converge, and form a strong 

 tendon, which passes up to be inserted on the ulnar crest of the 

 humerus. The contraction of this muscle assists in raising the 

 wing. 



//. — Dorsal Muscles of the Upper Extremity {15). 



Shufeldt numbers and names these as follow : — 



52. The latissimus dor si. 



53. The trapezius. 



54. The rhomhoideus. 



