326 THE MUSCULAR SYSTEM. 
(3) The radial origin is from the oblique line and middle third of the outer border 
of the radius by a thin fibro-muscular attachment. 
The muscle separates in the lower third of the forearm into four parts, each 
provided with a separate tendon which passes beneath the anterior annular liga- 
ment, crosses the palm of the hand, and enters the corresponding digital sheath, 
Within the digital sheath each tendon is split into two parts by the tendon of the 
flexor profundus digitorum; after surrounding that tendon the two parts are 
partially reunited on its deep surface, and are inserted, after partial decussation, 
in two portions into the sides of the second phalanx. 
The vineula accessoria form additional insertions of the muscle. They consist 
of the ligamenta longa and brevia. The ligamentum breve is a triangular band of 
fibres occupying the interval between the tendon and the digit for a short distance 
close to the insertion. It is attached to the front of the inter-phalangeal articu- 
: lation and the head of the first phalanx. 
ee The ligamentum longum is a long 
\.\ narrow band extending from the back 
of the tendon to the upper part of the 
anterior surface of the first phalanx. 
= icamienemmbesre The flexor sublimis digitorum muscle 
1) a oe eS eee is partially concealed in the forearm by 
yA EE 3 ee) eer the other more superficial muscles of 
HPN Hickbn euoroNDUE this group, and by the radial vessels 
| Af] PRX \ Picirorum and nerve. It conceals the deeper 
Firs? Lumpercat muscrn muscles of the forearm, the, mediam 
nerve, and the ulnar artery. Its inner 
EAST DORSAL ENTER border is in contact with the flexor 
carpi ulnaris, and in the lower half of 
Extensor rxpicis‘rexnon. the forearm with the ulnar vessels and 
nerve. The median nerve emerges at 
EXTENSOR COMMUNIS its outer border above the wrist, and 
P| at separates the muscle from the tendon 
of the flexor carpi radialis. At the 
wrist the four tendons are arranged in 
pairs, those for the middle and ring 
fingers in front, those for the fore and 
little fingers behind, and are enveloped 
Soave ee. les in a synovial sheath along with the 
Ia, 242,—THE TENDONS ATTACHED TO THE INDEX ae 
heaeanne tendons of the flexor profundus digi- 
torum beneath the anterior annular 
ligament. In the palm the tendons separate, and lying beneath the superficial 
palmar arch, conceal the tendons of the deep flexor and the lumbrical muscles. 
Within the digital sheaths on the fingers the tendons at first conceal those of the 
deep flexor; after being pierced by them, they are in turn concealed by these 
tendons at their insertion. 
Ligamentum_\ 
breve 
Ligamentum 
longum 
DrEP MUSCLES. 
The deep muscles on the front of the forearm are three in number: flexor 
profundus digitorum, flexor longus pollicis, and pronator quadratus. 
The flexor profundus digitorum is a large muscle arising from the ulna, the 
interosseous membrane, and the deep fascia of the forearm. Its ulnar origin 1s 
from the anterior and inner surfaces of the bone, extending up so as to include the 
inner side of the olecranon process, and embrace the insertion of the brachialis 
anticus into the coronoid process. It arises external to the ulna from the inner 
half of the interosseous membrane in its middle third, and internally from 
the deep fascia of the forearm behind the origin of the flexor carpi ulnaris. 
The muscle forms a broad thick tendon which passes beneath the anterior 
annular ligament, and divides in the palm into four tendons for insertion into the 
terminal phalanges of the fingers. The tendon associated with the fore finger is 
usually separate from the rest of the tendons in its whole length, Hach tendon enters 
