324 THE MUSCLES. 



two muscles in becoming intimately united with the capsular ligament of the 

 elbow articulation. Its movable insertion takes place on the anterior and 

 superior tuberosity of the large metacarpal bone, by the inferior extremity of its 

 tendon. 



Relations. — The muscular portion is covered by the antibrachial aponeurosis 

 and the short extensor of the forearm. It covers the anterior face of the radius, 

 as well as the elbow articulation ; outwards and behind, it is in contact with the 

 inferior extremity of the short flexor of the forearm or humeralis obliquus, the 

 aponeurosis of which adheres intimately to the arciform portion of the fibres of 

 the anterior extensor of the metacarpus, and appears to attach this muscle to the 

 deltoid imprint. Its tendon covers a small portion of the anterior aspect of the 

 radius, and enters the internal vertical groove channeled in front of the inferior 

 extremity of that bone ; afterwards it passes over the capsular ligament of the 

 carpus, and is maintained against that membranous expansion by a wide fibrous 

 sheath, through which it glides by the aid of two synovial membranes (Fig. 183). 

 This tendon is crossed above the knee by that of the oblique extensor, which 

 passes to its surface. 



Action. — The name of this muscle indicates its function ; it extends the 

 metacarpus on the forearm. 



2. Oblique Extensor of the Metacarpus (Extensor Metacarpi 

 Obliquus) (Figs. 179, 13 ; 181, 21 ; 182, 14). 



Synonyms. — Cubito-premetacarpeus, or radio-premetacarpeus — Girard. It is the repre- 

 sentative of the long abductor and short extensor of the thumb in Man. (Extensor metacarpi 

 obliquus vel parvus — Percivall. Badio-metacarpeus — Leyh.) 



Situation — Form — Structure — Direction. — A small muscle situated at the 

 internal side of the radius, beneath the anterior extensor of the phalanges, 

 penniform in shape, strongly aponeurotic, and terminated by a tendon which 

 turns obhquely round the anterior aspect of the radius, in passing downwards 

 and inwards to reach the oblique channel on the inferior extremity of that bone, 

 and to pass thence to the inside of the knee. 



Attachments. — It has its origin on the external side of the radius ; its 

 terminal tendon is fixed into the head of the internal metacarpal bone, by its 

 fibres becoming mixed with those of the internal ligament of the carpus. 



Relations. — It is covered by the anterior extensor of the phalanges and 

 the antibrachial aponeurosis. It successively covers the anterior face of the 

 radius, the tendon of the anterior extensor of the metacarpus, the radial groove 

 lodging its tendon, and in which it glides by means of a small synovial bursa, as 

 well as the internal ligament of the carpus. 



Action. — It extends the metacarpus, and may make it pivot from within 

 forwards. 



3. Anterior Extensor of the Phalanges (Extensor Pedis) 

 (Figs. 179, 14 ; 181, 15 ; 182, 9). 



Synonyms. — Epicondylo-prephalangeus — Girard. The extensor communis digitorum of 

 Man. (Eumero-prephalangeus — Leyh.) 



Situation — Direction — Extent — For7n — Strticture. — This is a long vertical 

 muscle, situated external to and behind the anterior extensor of the metacarpus, 

 which it resembles in being composed of a fleshy and a tendinous portion. The 



