_Origin._—From just below the summit of the antero-internal part of the head of the tarso-metatarsus, and from the adjacent shaft below, and from the tendon of the tibialis anticus. _Insertion._—Into the process at the superior part of the bone of the bony claw of the hallux. _Shape._—Slender, thin in diameter, with a long, slender tendon. _Relations._—Superiorly, with the antero-internal edge of the metatarsus and interiorly, its tendon with the top of the hallux. _Action._—Extends the hallux. =Extensor Brevis Digitorum.= _Location._—On the anterior surface of the metatarsus. [Illustration: FIG. 25.—Inner layer of muscles of the thigh of a hen. Outside view. _A._ Pad of fibrocartilage or meniscus of femoro-tibial articulation. 1, Inner semi-lunar fibrocartilage. 2, External semi-lunar cartilage. 3, Anterior border. _B._ Tarsal meniscus or pad of fibrocartilage. _C._ Articular surface of the tarsal joint. 1, Posterior ligamentum cruciatum genu. 2, Femoral tendinous insertion of tibialis anticus. 3, Ligamentum tibio-fibulare. 4, Ligamentum interosseum. 5, Ligamentum transversum of the meniscus. 6, Anterior ligamentum cruciatum genu. _D._ 1, Tibia. 2, Fibula. 3, Femur. 4, External ligamentum laterale genu. _E._ Inferior surface of the tail of a hen. 1, Infracoccygis. 2, Lateralis coccygis. _F._ Outside pelvic view. 1, Obturator ligament. 2, Tendon of the obturator internus. 3, Ligamentum oblongum. 4, Ligamentum capsulare. 5, Gemellus. _G._ Outside view of leg of a cock. 1, Soleus. 2, Flexor longus hallucis. 3, Flexor perforans digitorum profundus. 4, Extensor brevis hallucis. 5, Extensor brevis annularis. 6, Extensor longus digitorum. 7, Tendon of the tibialis posticus. _H._ 1, Transversalis abdominalis. 2, Cotyloid cavity. ] _Origin._—By a small fleshy belly to the anterior part of the proximal end of the metatarsus. _Insertion._—It becomes tendinous about the middle third of the metatarsus. Extending down the anterior face of the metatarsus it is inserted to the inner tubercle of the base of the first phalanx of the outer or fourth toe. _Shape._—Long, slender. _Relations._—Posteriorly with the metatarsus. _Action._—Pulls the fourth toe upward and inward. =Flexor Hallucis Brevis.= _Location._—Postero-internal side of the metatarsus. _Origin._—Side and lower margin of the inner aspect of the hypotarsus of the tarso-metatarsus and from the shaft of this bone immediately below it. _Insertion._—Winds round inner side of basal joint of the hallux and is inserted on its under side. _Shape._—Small flat muscle gradually tapering into a tendon. _Relations._—Posteriorly with the metatarsus. _Action._—To flex the hallux. =Extensor Annularis Brevis.= _Location._—On postero-external side of metatarsus. _Origin._—External aspect of the hypotarsus and the shaft below. _Insertion._—Supero-external part of the basal phalanx of the fourth toe.