The muscles chiefly concerned in producing movements of the joints of the upper limb are as follows :

Shoulder.

Flexion : pectoralis major, anterior fibres of deltoid.

Extension : latissimus dorsi, posterior fibres of deltoid, teres major.

Abduction : deltoid, supra-spinatus.

Adduction : pectoralis major, coraco-brachialis, teres major, latissimus dorsi.

Circumduction : combinations of these muscles.

Rotation, inwards: subscapularis, pectoralis major, latissimus dorsi, teres major.

Rotation, outwards: supra-spinatus, infra-spinatus, teres minor.

Elbow.

Flexion : biceps, brachialis anticus, pronator radii teres, supinator longus.

Extension : triceps, anconeus.

Supination : biceps, supinator longus, supinator brevis.

Pronation : pronator radii teres, pronator quadratus, flexor carpi radialis.

Wrist.

Flexion : flexor carpi radialis, flexor carpi ulnaris, palmaris longus, flexor profundus digitorum, flexor longus pollicis.

Extension : extensor carpi radialis longus, extensor carpi radialis brevis, extensor carpi ulnaris.

Abduction : flexor carpi radialis.

Adduction : flexor carpi ulnaris.

Fingers.

The movements of the first phalanx are flexion, extension, abduction, adduction.

Flexion : interosseous and lumbrical muscles.

Extension : extensor communis and the special extensors of index and little fingers.

Abduction : dorsal interossei, abductor minimi digiti.

Adduction : palmar interossei.

Flexion of second phalanx is by flexor sublimis.

Flexion of third phalanx is by flexor profundus.

Fig. 36.—Superficial Muscles of Shoulder and Arm from Before (Right).

1, Deltoid; 2, pectoralis major; 3, biceps; 4, brachialis anticus; 5, long-head of biceps ; 6, pronator radii teres ; 7, supinator longus.

Fig. 37.—Superficial Muscles of Front of Forearm and Hand (Right). 1, Supinator longus ; 2, pronator radii teres ; 3, flexor carpi radialis ; 4, flexor carpi ulnaris ; 5, palmaris longus ; 6, palmaris brevis ; 7, abductor pollicis ; 8, adductor pollicis ; 9, abductor minimi digiti.

Fig. 38.—Superficial Muscles of Shoulder and Arm from Behind (Right).

1, Deltoid; 2, infra-spinatus; 3, triceps; 4, brachialis anticus; 5, supinator longus ; 6, serratus magnus ; 7, teres minor ; 8, teres major.

Fig. 39.—Superficial Muscles of Back of Forearm and Hand (Right).

1, Flexor carpi ulnaris ; 2, supinator longus ; 3, ext. carpi radialis longus ; 4, ext. communis digitorum ; 5, ext. carpiradialis brevis ; 6, ext. carpi ulnaris; 7, dorsal interossei ; 8, posterior annular ligament; 9, ext. ossis metacarpi; 10, ext. primi internodii pollicis; 11, ext. minimi digiti.

Extension of these joints is by interossei and lumbricales and the extensor communis, into the tendons of which they are inserted.

There are twenty muscles on the forearm. They are divided into flexors, extensors, pronators and supinators.

The flexors and pronators consist of a deep and a superficial layer, and are on the front and inner side of the forearm.

The superficial muscles are five ; they arise by a common tendon from the inner condyle of the humerus. They are the pronator radii teres, flexor carpi radialis, palmaris longus, flexor carpi ulnaris, and flexor sublimis digitorum.

The deep muscles arise from the bones of the forearm : they are the flexor profundus digitorum, flexor longus pollicis, and pronator quadratus.

The extensors and supinators also consist of a deep and a superficial layer, and are on the back and outer side of the forearm.

The superficial muscles are seven : the supinator longus extensor carpi radialis longus, extensor carpi radialis brevis, extensor communis digitorum, extensor minimi digiti, extensor carpi ulnaris, and anconeus ; the two first arise from the external supra-condylar ridge of humerus, the four following arise by a common tendon from the external condyle of humerus, the anconeus arises by a distinct tendon from same condyle.

The deep muscles arise from the bones of the forearm ; they are the supinator brevis, the three extensors of the thumb and the special extensor of the index finger.

The short muscles of the hand are all in the palm : four form the ball of the thumb, called the thenar eminence ; three form the ball of the little finger, called the hypothenar eminence; one deepens the hollow of the palm when contracted.

Four tapering muscles, the lumbricales (fiddlers' muscles), arise in the tendons of the flexor profundus digitorum.

Four dorsal and three palmar interosseous muscles arise from the sides of the metacarpal bones.

The muscles which flex the forearm are on the front of the humerus ; those which extend the forearm are on the back of the humerus ; those which act on the humerus are on the scapula, back, and chest.