182 



THE MUSCLES. 



FIG. 87. RADIUS AND ULNA, 

 Medial or Flexor Side, with 

 M. pronator quadratus and the 

 Areas of Attachment of Other 

 Muscles. 



a, M. pronator quadratus; l>, 

 tendon of M. biceps; t, conjoined 

 tendon of M. brachialis and M. 

 clavobrachialis ; d, insertion of 

 caput longum of M. triceps; e, 

 insertion of short portion of caput 

 mediale of M. triceps; f, origin 

 of M. flexor carpi ulnaris; g, 

 origin of first head of M. flexor 

 profundus digitorum; A, origin 

 of fifth head of M. flexor profun- 

 dus digitorum; t, intermediate 

 portion of caput mediale of M. 

 triceps. 



The second head has origin (Fig. 

 82, ;/) 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, ) has 

 origin (Fig. 82, o) by a strong tendon 

 from the medial epicondyle of the 

 humerus, between the palmaris (/) 

 and flexor radialis (;//). 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. 



Theyf/?/^ or radial head (Fig. 75, 

 q; Fig. 77, ?/) has origin (Fig. 87, //) 

 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. 



