MUSCLES OF THE THORACIC LIMBS. 157 



infraspinatus (Fig. 75, c). The origin may pass toward the 

 vertebral border of the scapula onto the infraspinatus muscle 



(Fig- 75, 0- 



Insertion (Fig. 81, //) by a flat tendon upon the deltoid 

 ridge of the humerus, nearly parallel to that of the pectoralis 

 major. 



Relations. Outer surface with the integument and at the 

 insertion with the acromiodeltoideus (Fig. 75,/). Inner sur- 

 face with the infraspinatus (c], teres minor (Fig. 80, c], caput 

 laterale (Fig. 75, //), and caput longum (Fig. 75, g] of the 

 triceps muscle. 



Action. Flexes the humerus and rotates it outward. 



M. acromiodeltoideus (Fig. 75, /; Fig. 68, g]. A flat 

 muscle which overlies the distal end of the spinodeltoideus 

 (Fig. 75, r). It connects the acromion with the humerus. 



Origin (Fig. 76, d}. From the glenoid border of the 

 acromion, and sometimes the adjacent metacromion as far as 

 the tip. 



Insertion. Mostly upon the outer surface of the spinodel- 

 toideus (Fig. 75, c]. The outer fibres are continued to the 

 bone, especially at the lateral border of the muscle, and are 

 inserted along a line ventrad of the line of insertion of the 

 spinodeltoideus, and extending farther distally (Fig. 81, g]. 

 Some of the outer fibres pass into the brachialis (Fig. 80, Ji], 



Relations. Outer surface with the integument and the 

 clavobrachial (Fig. 68, e). Inner surface with the infraspinatus 

 (Fig. 75, c], teres minor (Fig. 80, c), spinodeltoid (Fig. 75, e), 

 and caput laterale of the triceps (Fig. 75, //). 



Action. Like that of the spinodeltoid. 



M. clavobrachialis (Fig. 65, k\ Fig. 68, e). A flat, tri- 

 angular muscle on the cranial surface of the shoulder, forming 

 a direct continuation of the clavotrapezius (Fig. 68, d}. These 

 two are frequently described as constituting a single muscle, 

 the cephalohumeral or cephalobrachial. (The clavobrachial is 

 frequently given the name clavodeltoid ; as its homology with 

 the human clavodeltoid appears doubtful, it seems well to use 

 the name clavobrachial, as proposed by Clasen.) 



Origin. Its superficial fibres are continuations of the 



