This is a thick, broad, fleshy muscle to which the croup owes its characteristic roundness. In a forward direction it extends for some distance over the loins, and terminates behind in the upper extremity of the femur or thigh-bone.
Origin. - (l) From the superior surface of the longissimus dorsi in front. (2) From the superior or dorsal surface of the ilium, and the sacro-sciatic and the ilio-sacral ligaments.
Insertion. - By three branches into the upper extremity of the femur.
Action. - To extend the thigh on the pelvis and incline the entire limb outwards. When the hind limbs are fixed it assists in rearing. Acting from before as a fixed point it takes part in kicking.