MUSCLES OF THE ANTERIOR LIMBS. 319 



Form — Structure — Situation — Direction. — This is a very thick muscle, almost 

 entirely fleshy, voluminous in its superior part, and constricted inferiorly. It 

 is lodged in the musculo-spiral groove of the humerus, the direction of which it 

 exactly follows as it turns round the bone to cover, successively, its posterior 

 face, external face, anterior face, and the capsule belonging to the elbow 

 articulation, until it finally reaches the inner side of the radius. 



Attachments. — The muscular fibres have their fixed insertion on the posterior 

 face of the humerus, below the articular head. They terminate, inferiorly, on 

 a flat tendon, which they almost entirely cover. This tendon ghdes in a trans- 

 verse groove situated on the inner face of the radius, below the bicipital tube- 

 rosity, and afterwards passing under the internal hgament of the elbow- joint, 

 it divides into two very short fasciculi ; one of these goes to the radius, and the 

 other to the ulna, where it is mixed up with the bundles of arciform fibres which 

 unite, on the inner side, the two bones of the forearm. 



Relations. — We already know the parts this muscle covers. It is covered, 

 inwardly, by the adductor of the arm and the middle extensor of the forearm ; 

 posteriorly and externally, by the large and short extensors of that bone. Its 

 inferior extremity, comprised between the anterior extensor of the metacarpus 

 and the flexor brachii, passes below the antibrachial band of the latter, as under 

 a fibrous bridge. 



Action. — It is simply a flexor of the forearm. 



B. PosTERioE Brachial Region. 



This is composed of four muscles, which have their movable insertion in 

 common on the summit of the olecranon, and are consequently designated 

 olecranian muscles. With reference to their action, they are also designated 

 extensors of the forearm, and are distinguished into long, short, middle, and small.^ 



The first three of these muscles resemble the triceps hrachialis (or triceps 

 extensor cuUti) of Man — the large extensor representing the long or middle portion, 

 the short extensor the external, and the middle extensor the internal. The small 

 extensor takes the place of the anconeus or elbow muscle of some authorities. 



Preparation.— The muscles of this region ought to be studied before those of the preceding 

 ■region. To dissect the large and short extensors, it is necessary to lay the limb on its inner 

 face, remove the slight fibrous layer wliich covers these two muscles, and raise the abductors 

 of the arm, which in great part conceal their origin. The limb is kept in the same position 

 for the dissection of the small extensor, which is not easily accomplished, as it is almost 

 entirely concealed by the short extensors, which, besides, closely adhere to it. To dissect the 

 long and middle extensors, it suffices to turn the limb on its external surface and cut away the 

 vessels, nerves, and lymphatics which partly cover the latter; care must also be taken to 

 isolate the muscle annexed to the latissimus dorsi. 



1. Large Extensor of the Forearm (Caput Magnum), or Long Portion 

 OF the Triceps Brachialis (Figs. 179, 7 ; 181, 7). 



5?/non«/ms.— Scapulo-olecranius magnus— G/rarfi. The long portion of the triceps brachi- 

 alis of Man. (Portion of llie caput magnum of the triceps extensor brachii— Percivall.) 



Volume— Form— Situation.— An enormous, short, and triangular muscle, 



> In veterinary -works, and in preceding editions of this work, there has been described in 

 this region a fifth muscle— the lonq extensor of the forearm. This has now been moved to the 

 region of the back and loins, wliere it is annexed to the latissimus dorsi, because of its relations 

 with that muscle. 



