212 MYOLOGY. 



are either flexors, extensors, abductors, adductors, or rotators, but 

 in the horse the lastj are comparatively few, limited in their 

 action, and nearly all extrinsic, the joints of the horse's limbs 

 below the shoulder and hip allowing very slight rotatory motion. 



Muscles of the Pectoeal Limb. 

 These may be conveniently divided into the following regions: — 

 Scapular .... The shoulder. 



Brachial .... The arm. 



Antibrachial .... The fore-arm. 



Metacarpal .... The foot (hand). 



Scapular Region. 



Externally the region is covered by the strong scapular fascia, 

 and comprises an external group of four and an internal of three 

 muscles. 



External Scapular Group. 



Teres externus. I Postea-spinatus. 



Antea-spinatus. | Postea-spinatus minor. 



TERES EXTERNUS. 



{Scaiiulo-humeralis Magnus. ) 



(Fig. 78. c.) 



This is the long abductor of the arm, which corresponds to 

 the deltoid of man. Situated on the outer and posterior part of 

 the shoulder, it consists of two portions, anterior and posterior. 

 The posterior or larger portion is triangular in form and very 

 fleshy, the fibres extending obliquely downwards and forwards \ 

 it is lodged in a depression in the caput magnum. The anterior 

 or superior portion is thin, and aponeurotic above, extending over 

 the postea-spinatus muscle, to which it is adherent. 



Attachments. — The posterior section arises from the dorsal 

 angle and posterior costa of the scapula ; the anterior by strong- 

 fascia from a tubercle on the spine of the scapula, and the scapular 

 fascia. They unite inferiorly, and by tendinous and fleshy fibres 

 are inserted to the deltoid ridge of the humerus below the inser- 

 tion of the postea-spinatus minor. 



