THE MUSCLES 79 



A muscle of medium strength arising from the dorsal surface of the 

 pro-coracoid. The fibres pass caudalwards to the posterior margin 

 of the coracoid where they turn sharply round lateralwards, and are 

 inserted on the crista dorsalis humeri. The M. anconaeus coracoideus, 

 and the MM. coraco-brachialis longus et brevis lie on the ventral 

 side, and the M. anconaeus scapularis medius is on the dorsal side 

 of this muscle. 



Innervation : By the N. subscapulars from the third spinal nerve. 



Function : The contraction of the muscle draws the arm backwards 

 and thus, if the foot is resting on the ground, it serves to advance the 

 body. 



M. anconaeus. Furbringer (1873); Hoffmann (1873-8); Rylkoff 

 (1924); Osawa (1902). 



Anconaeus internus et externus .... Funk (1827) 



Triceps brachii extensor (24) ..... Carus (1828). 



Strecker des Vorderarms . . . . . Meckel (1828) 



Scapulo-humero-olecranien, triceps .... Duges (1834) 



Streckmuskelmasse ..... Stannius (1854-6) 



Triceps brachii s. anconaeus . Riidinger (1868); Mivart (1869) 



Triceps and coraco-olecranalis . . . Humphry (1872) 



Extenseur de I'avant-bras (81-3) .... Perrln (1899) 



The M. anconaeus arises from the shoulder-girdle and humerus by 



four heads which unite distally, to a greater or lesser extent, to form 



a powerful muscle which is inserted on the olecranon process of the 



ulna. In general it is innervated by the extensor nerves, 2ind functions 



as extensor of the fore-arm. The details of its several components 



may be considered separately. 



Caput (a). M. anconaeus scapularis medialis (m.a.s.m.). Furbringer 

 (1873); Hoffmann (1873-8); Rylkoff (1924). 



Anconaeus longus ....... Eisler (1895). 



Tete anterieur (81) ...... Perrln (1899). 



Anconaeus caput scapulare ..... Osawa (1902). 



This head arises from the scapula at the posterior margin of the 

 glenoid cavity. The main tendon arises a little towards the mesia/ side 

 of the scapula, but retains a strong fibrous connexion with the whole 

 posterior region of the capsule surrounding the joint. The muscle is 

 thin and flat, and is separated from the M. anconaeus coracoideus 

 by the entry of the extensor nerves and the V. brachialis medialis into 

 the arm, as well as by the insertion of the M. subscapularis. 



Innervation: By twigs from theN.extensorius caudalis(cf. p. 166). 

 Function: See above. 



