eS Pe < ’ 
2s 
MUSCLES ON THE BACK OF THE FOREARM. 335 
Muscles. Nerves. Origin. 
C. Supinators and Extensors. 
Brachio-radialis Py C506: 
soa See) eee fo ee Musculo-spiral —. : AL YAS 
Extensor carpi radialis longior f Jeo. 
Extensor carpi radials brevior | Or & % 
Extensor communis digitorum Posterior interosseous | 67.8 
‘z Je * . . 
Extensor minimi digiti | (musculo-spiral) J 
Extensor carpi ulnaris 
Extensor longus pollicis 
Extensor indicis 
Anconeus as : : ‘ Musculo-spiral —. Co 1s 8: 
Supinator radii brevis C.6 
Extensor ossis metacarpi pollicis} 
Extensor brevis pollicis : Posterior interosseous CnG63.75,8 
4 
ACTION OF THE MUSCLES OF THE FOREARM AND HAND. 
The muscles of the forearm and hand are concerned in the movements of the elbow, wrist, and 
_ joints of the fingers. 
In the majority of cases the muscles act upon more than one joint. 
1, Action on the Elbow Joint.—It has been shown already (p. 330) that flexion and ex- 
tension of the elbow are assisted by certain of these muscles. The flexor muscles are the pronator 
_ radii teres, and the flexor muscles of the wrist and fingers, along with the brachio-radialis and 
extensors of the wrist and fingers (during pronation). The extensors are the supinator brevis and 
anconeus, and the extensor muscles of the wrist and fingers (during supination). 
2. Pronation and supination of the hand are performed by special muscles, aided by muscles 
which act also upon other joints. The brachio-radialis assists in flexion and pronation on the one 
hand, and in extension and supination on the other hand. 
Pronation. Supination. 
Pronator radii teres Supinator radii brevis 
Pronator quadratus Biceps 
Brachio-radialis Brachio-radialis 
Flexor carpi radialis Extensors of thumb and fingers 
Weight of the limb Weight of the hmb 
3. Action on the Wrist Joint.—The movements at the wrist joint are flexion and extension, 
abduction and adduction. The following muscles produce these movements :— 
a. Flexion and Extension. b. Adduction and Abduction. 
Flexor carpi radialis | Extensors of the wrist | Flexor carpi ulnaris Flexor carpi radialis 
Palmaris longus Extensors of thumb | Extensor carpi ulnaris | Extensors of wrist 
Flexor carpi ulnaris | and fingers | Extensors of thumb 
Long flexors of 
thumb and fingers | 
4. Movements of the Fingers.—T'wo separate series of movements occur in relation to the 
articulations of the fingers: flexion and extension (at the metacarpo-phalangeal and inter- 
-phalangeal joints), and abduction and adduction (only at the metacarpo-phalangeal joints). The 
movements and the muscles concerned are given in the following table :— 
a. Flexion and Extension. 
Flexor sublimis digitorum Extensor communis digitorum 
Flexor profundus digitorum Extensor indicis 
Lumbricales \ (acting on the metacarpo-| Extensor minimi digiti 
Interossei JS phalangeal articulations) | Lumbricales )\ (acting on the inter -phal- 
Flexor brevis minimi digiti Interossei J angeal articulations) 
