THE MUSCLES OF THE UPPER EXTREMITY. 117 



must carefully remove the common integuments of 

 the arm and proximal moiety of the forearm ; divide 

 the tendons of the patagii muscles ; and dissect away 

 all the superfluous adipose tissue, fascia and vessels. 

 The biceps will then be seen to be a large sub- 

 fusiform muscle, occupying the anterior aspect of the 

 arm. Its proximal third is composed of a broad, 

 flat tendon covering the top of the shoulder-joint. 

 This portion is divided into two heads, the aperture 

 of the division being a wide obtuse angle, with its 



O o ' 



apex opposite the humeral head. This bifurcation 

 gives rise to the long and short heads of the biceps, 

 the former being inserted into the outer aspect of the 

 head of the coracoid just beyond the glenoid cavity, 

 while the short head is attached to the distal angle 

 of the ulnar tuberosity of the humerus (Figs. 24, 

 28, 29, and 32). This flat, proximal tendon extends 

 somewhat beyond the bifurcation, but soon is usurped 

 by the commencement of the carneous portion of the 

 muscle, which is correspondingly broad and subcom- 

 pressed. After forming the muscular belly, the fibres 

 as they pass down rapidly converge to an apex, and 

 finally form the strong cord-like tendon for insertion, 

 which passes to the ulna and is attached to that 

 bone, immediately in front of the articular cavity 

 for the trochlear surfaces of the distal extremity of the 

 humerus. 



The biceps is a powerful flexor of the forearm, and 

 this is its chief function. 



70. The deltoid 1 is partially divided into two 

 portions ; one long narrow head arises tendinous from 



1 A very excellent account of the deltoid muscle in birds is also 

 given us by Gadow (loc. cit., p. 230), together with a synonymy 

 which is herewith republished ; 



