18 THE ANATOMY OF THE HORSE. 



scapular fascia, and by its posterior portion from the dorsal angle of 

 the scapula. It is inserted into the deltoid (external) tubercle of the 

 humerus. 



Action. — To abduct the humerus, and rotate it outwards. Acting 

 with the teres major, it is also a flexor of the shoulder. 



Directions. — The last-mentioned muscle should be carefully cut at 

 the level of the shoulder, and reflected upwards and downwards. This 

 will expose the divisions of the circumflex vessels and nerve, branches 

 of which will be seen entering the muscle, and it will at the same time 

 bring into view the next muscle. 



The Teres Minor (Plates 7 and 8). |This small muscle arises from the 

 posterior border of the scapula, from the rough lines at the lower part 

 of the infraspinous fossa, and from the small tubercle on the outer rim 

 of the glenoid cavity. Its tendon, which is crossed by a glistening 

 band of fascia, is inserted into the lower half of the ridge running 

 upwards from the deltoid tubercle to the external tuberosity. 

 Action. — The same as the preceding muscle. 



The Infraspinatus (subspinatus, or postea-spinatus) (Plates 7 and 8) 

 occupies the greater part of the fossa of the same name. It arises from 

 the whole extent of the fossa, and from the inner surface of the scapular 

 fascia. It possesses two tendons of insertion, the outer of which passes 

 over the convexity of the external tuberosity, a synovial bursa being 

 interposed, and is inserted into the upper half of the ridge connecting 

 that tuberosity to the deltoid tubercle. If this tendon be cut where it 

 plays over the convexity, the synovial bursa will be opened, and, 

 at the same time, the inner insertion of the muscle into the inside 

 of the convexity will be exposed. This inner tendon is more fleshy 

 than the outer, and is in contact with the capsular ligament of the 

 shoulder. 



Action.— It abducts the humerus, and rotates it outwards. 

 The SuPEASPiNATUS (antea-spinatus) (Plates 7 and 8) fills the whole of 

 the fossa of the same name, and takes origin from it as well as from 

 the scapular fascia. It is bifid inferiorly, having an inner tendon 

 inserted into the internal tuberosity at its highest point, and an outer 

 tendon inserted into the corresponding point of the external tuberosity. 

 These two tendons are in contact with the capsular ligament of the 

 joint, and the tendon of origin of the biceps emerges from between them. / 

 Action. — It is an extensor of the shoulder-joint. 



Directions. — The outer aspect of the triceps extensor cubiti is here 

 seen; and when its surface has been cleaned, a line will be observed 

 running from the shoulder to the point of the elbow. Careful dissection 

 downwards into the mass, along this line, will separate the caput mag- 

 num (ah-eady described) from the caput medium, which lies below it. 

 AYhile the surface of the muscle is being cleaned, some small cutaneous 



