Brachialis muscle

The brachial muscle originates on the caudal surface of the proximal humerus, just distal to the humeral neck and extends over the lateral surface of the humerus in the spiral groove of humerus, and finally reaches the medial side, where it inserts on the radial and the ulnar tuberosities. 

In the horse, the brachial muscle ends with one tendon on the medial aspect of the radius, just distal to the biceps muscle of the forearm and one branch passes under the medial collateral ligament to insert on the interosseous membrane of the elbow joint.

Origin: Caudal on neck of humerus

Insertion: medial on radius and ulna

Action: flexor the elbow joint

Nerve: Musculocutaneous nerve