MUSCLES OF THE THORACIC LIMBS. 157 
infraspinatus (Fig. 75, ¢). The origin may pass toward the 
vertebral border of the scapula onto the infraspinatus muscle 
(Fig. 75, c). 
. Lusertion (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, 4%), 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, ¢). 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. 
Lnsertion.—Mostly upon the outer surface of the spinodel- 
toideus (Fig. 75, ¢). 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, ¢). 
Some of the outer fibres pass into the brachialis (Fig. 80, %). 
Relations.—Outer surface with the integument and the 
clavobrachial (Fig. 68, ¢). Inner surface with the infraspinatus 
(Fig. 75, ¢), teres minor (Fig. 80, ¢), spinodeltoid (Fig. 75, ¢), 
and caput laterale of the triceps (Fig. 75, 4). 
Action.—Like that of the spinodeltoid. 
M. clavobrachialis (Fig. 65, 4; Fig. 68, ¢).—A flat, tri- 
angular muscle on the cranial surface of the shoulder, forming 
a direct continuation of the clavotrapezius (Fig. 68, @). 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 
