l6 Leach, The Myology of the Bell-Magpie. [^^^ 



Emu 



July 



IV . — Muscles of the Brachium (4). 



69. The biceps. 



70. The deltoid. 



71. The triceps. 



72. The hrachialis anticus. 



69. The biceps [21] [23] is a very large and powerful muscle 

 arising as a flat tendon from the outer part of the head of the 

 coracoid and from the ulnar tuberosity of the humerus. The 

 muscle passes over the pectoralis major and forms a big muscular 

 belly. The fibres converge to a strong tendon inserted in the 

 ulna. It is a strong flexor of the forearm. 



70. The deltoid [22] is distinctly divided into two portions. 

 The first portion is long and narrow, arising from the anterior 

 part of the scapula and neighbouring part of the clavicle. This 

 narrow band runs about half-way down the humerus, where it 

 joins the big muscular part of the deltoid, which arises fleshy from 

 the OS humero-scapulare and the outer surface of the humerus 

 down nearly the whole length of the shaft, except about the 

 insertion of the latissimus dor si (52). Both parts converge to 

 form a strong subcylindrical tendon, which is inserted into the 

 proximal side of the external condyle of the humerus. This 

 muscle may be of taxonomic value, as it differs in other birds I 

 have examined. 



71. The triceps [22] [22a] [23] [23a] is divided, as in the 

 Raven, into three portions, one oi which, the scapular head, is 

 entirely separated from the rest. 



The scapular head arises from the upper side of the scapula 

 just behind the glenoid cavity. It forms a long, thick muscle 

 strand that passes down under the supraspinatiis (57) and the 

 teres et infraspinatus (58) to be inserted as a strong tendon at the 

 proximal end of the ulna. 



The internal and external heads of the triceps are in close con- 

 nection except at their proximal ends. They arise on the back 

 of the humerus, allowing the supraspinatiis (57) to be inserted 

 between them. The external head further divides to allow the 

 teres et infraspinatus (58) to be inserted. The two heads soon 

 fuse, and a strong muscle, closely attached to the humerus, runs 

 down to form a broad, flat tendon, which passes across to be 

 inserted into the radial side of the olecranon process of the ulna. 

 The enclosing fascia binds the three parts of the triceps together. 

 This muscle is the powerful extensor of the arm. 



72. The hrachialis anticus [23] is a small, narrow muscle passing 

 across from the inner side of the distal extremity of the humerus 

 to the lateral surface of the proximal end of the ulna. 



V. — Muscles of the Forearm and Hand. 

 Thirteen muscles are named by Shufeldt, as follow : — ■ 



73. The extensor metacarpi radialis longior. 



