This muscle extends the digit or digits into which it is inserted. It also assists in the movement of extension of the hand as a whole. =Posterior Ulnar= (_Extensor carpi ulnaris_) (Fig. 73, 11; Fig. 74, 17; Fig. 75, 18).--Designated by veterinary anatomists as the _external flexor of the metacarpus_,[27] or _external cubital_, this muscle is situated in the posterior region of the external surface of the forearm, behind the lateral extensor of the phalanges. [27] Certain authors give it the name of _ulnar extensor of the wrist_. It is true that in the human being this is its action; but in quadrupeds, owing to its insertion into the pisiform, it draws the hand into the position of flexion. It arises from the epicondyle; its fleshy body, thick but flattened, is directed vertically towards the carpus, and its tendon is inserted into the external part of the superior extremity of the metacarpus, after having given off a fibrous band, which takes its attachment on the pisiform. It is inserted, in the cat and the dog, into the superior extremity of the fifth metacarpal; in the pig to the external metacarpal; in the ox to the external side of the canon-bone; in the horse to the superior extremity of the external rudimentary metacarpal. This muscle flexes the hand on the forearm, and in animals in which the radio-carpal articulation permits, by its formation, it inclines the hand slightly outwards--that is, abducts it. =Anconeus= (Fig. 72, 17; Fig. 73, 13).--We have already stated (p. 174) that the anconeus is included with the triceps brachialis in zoological anatomy, and that veterinary anatomists give it the name of _small extensor of the forearm_.[28] [28] It is also called by some authors, the _small anconeus_. In the dog it recalls, as to position, the human anconeus, but with this difference--that, in the latter, the anconeus, triangular in outline, has one of its angles turned outwards (the epicondyloid attachment) and one of its sides turned towards the olecranon. Here it is entirely the opposite. The anconeus, similarly triangular, is broader externally. At this level it takes its origin from the external border of the humerus, the epicondyle, and the external lateral ligament of the articulation of the elbow; thence its fibres converge towards the external surface of the olecranon, to be there inserted.