T82 
Fic. 87.,—-RADIUS AND ULNA, 
Medial or Flexor Side, with 
M. pronator quadratus and the 
Areas of Attachment of Other 
Muscles. 
a, M. pronator quadratus; 4, 
tendon of M. biceps; ¢, conjoined 
tendon of M. brachialis and M. 
clavobrachialis; @, insertion of 
caput longum of M. triceps; e, 
insertion of short portion of caput 
mediale of M. triceps; /, origin 
of M. flexor carpi ulnaris; g, 
origin of first head of M. flexor 
profundus digitorum; 4, origin 
of fifth head of M. flexor profun- 
dus digitorum; 7, intermediate 
portion of caput mediale of M. 
triceps. 
THE MUSCLES. 
The second head has origin (Fig. 
82, 2) from the distal end of the 
medial epicondyle of the humerus 
between the flexor ulnaris and the 
third and fourth heads of the profun- 
dus. It may be very closely attached 
to these muscles at their origins. Its 
tendon joins the radial border of the 
tendon of the first head. From this 
junction the radial part of the flexor 
sublimis arises. 
The third head (Fig. 77, u) has 
origin (Fig. 82, 0) by a strong tendon 
from the media] epicondyle of the 
humerus, between the palmaris (/) 
and flexor radialis (#7). Its tendon 
forms the radial part of the common 
tendon. 
The fourth head has origin by a 
strong tendon from the medial epicon- 
dyle of the humerus just ventrad of 
the origin of the second head and the 
flexor ulnaris, to which many of its 
fibres are attached. Its tendon forms 
the middle and superficial part of the 
common tendon. 
The fifth‘or radial head (Fig. 75, 
q; Fig. 77, u’) has origin (Fig. 87, 2) 
from the middle third of the ventral. 
surface of the shaft of the radius over 
an area limited by two oblique bony 
ridges; from the adjacent parts of the 
interosseous membrane; and from the 
ventral part of the medial surface of the 
shaft of the ulna between a point about 
two centimeters distad of the semi- 
lunar notch and the junction of the 
middle and distal thirds of the shaft. 
