MUSCLES OF THE THORACIC LIMBS. 
183 
Its very thick tendon forms the middle and deep part of the 
common tendon. 
The common tendon (Fig. 88, c’) 
covers the carpus and metacarpus ven- 
trally. It divides into five tendons (c) 
which pass to the five digits and are zz- 
serted into the bases of the terminal 
phalanges. Those of the first four digits 
perforate the tendon of the flexor sublimis 
(2) at the base of the first phalanx of each 
digit. At the same place each passes 
through a fibrous pulley-ring attached to 
the base of the phalanx. Each then passes 
through a second pulley-ring (2) near the 
head of the phalanx and is finally inserted 
into the base of the terminal phalanx. 
Relations. —Outer surface with the 
pronator teres (Fig. 77, ¢), flexor carpi 
radialis (Fig. 77, 7), palmaris longus (s), 
flexor carpi ulnaris (2), integument, and 
extensor carpi ulnaris (Fig. 75, 0). Inner 
surface with the radius, ulna, interosseous 
membrane and pronator quadratus (Fig. 
87, 2). 
Action.—Flexor of all the digits. 
M. pronator quadratus (Fig. 87, a). 
—A thick quadrangular muscle whose 
fibres run obliquely between the distal 
ends of the ulna and radius. 
Origin by fleshy fibres from about the 
distal half of the ventral (flexor) surface 
or border of the ulna and from the interos- 
seous membrane adjacent to the area. 
The fibres pass obliquely distad toward 
the radial side to their 
Insertion by fleshy fibres into the ven- 
tral (flexor) surface of the radius distad of 
Fic, 88.—ARRANGEMENT 
OF THE TENDONS of 
M. palmaris longus, M. 
flexor sublimis digito- 
rum, and M, flexor pro- 
fundus digitorum, with 
Mm. lumbricales. 
The integument, fibrous 
pads, and the palmaris 
longus (except the ends of 
its tendons) have been re- 
moved; the flexor sublimis 
has been cut. a, cut ends 
of tendons of M. palmaris 
longus; 4, tendons of M. 
flexor sublimis digitorum, 
ulnar division; 4’, radial 
part of M. flexor sublimis 
digitorum; c¢, tendons of 
M. flexor profundus digi- 
torum (¢, the common ten- 
don); @, M. abductor digi- 
ti quinti; e, M. flexor brevis 
digiti quinti; 4, Mm. lum- 
bricales (_/’, their tendons). 
I, transverse ligament of 
wrist; 2, annular ligaments. 
the area of origin of the fifth head of the profundus. 
