98 



Anatomy of Skeleton 



just below and internal to this structure to be attached to the radius. Articulate the 

 two bones, and it will be seen that the tubercle of the radius lies in front of the ulnar 

 origin of Supinator brevis : this can be seen in Fig. 78. During pronation the tubercle 

 turns back and with the attached tendon glides on the front of these aponeurotic 

 fibres, so that another bursa is placed on this aspect of the tendon and extends forward 

 to come also between it and the oblique ligament : this bursa is frequently replaced 

 by smooth " semi-bursal " areolar tissue. 



The oblique ligament is possibly a modified part of the ulnar origin of Flexor longus pollicis : 

 the interosseous border of the radius commences just below and rather behind the insertion of the 

 ligament, but as the fibres of the membrane arising here run in the opposite direction an interval 



FIG. 78. The right-hand drawing is from an ulna to show the small portion of the 

 olecranon which is formed from the two epiphysial centres, and the others illustrate 

 the position and relations of the burss on the tendon of Biceps. One of these is 

 between tendon and radius, the other between tendon and oblique ligament internally 

 and Supinator brevis behind, occupying the greater part of the triangular area below 

 the lesser sigmoid cavity. This second bursa is often wanting. 



is left between them covered in behind by the lower fibres of Supinator brevis, and the posterior 

 interosseous artery runs through this interval to pass under the lower margin of the muscle. 



The relations and attachments on the shaft of the bone are shown in Figs. 77 and 

 79. Examination of the shaft soon makes it evident that it has been moulded in a 

 general way, like so many bones, by the influence of the different muscle-groups that 

 can affect it : thus the extensors and flexors, which act in planes more or less parallel 

 with the bone, have hollow surfaces that afford origin to them, whereas the direct 

 pressure of the Supinator brevis has a stronger convex surface of cylindrical shaft to 

 withstand it. In this way the oblique line on the front surface may be looked on as a 

 primary ridge, but there is also a secondary marking to be found on it, for the aponeu- 

 rotic origin of Flexor sublimis : the origin is aponeurotic owing to the pressure of the 

 overlying Pronator teres, and it may be very thin, and the secondary marking may not 

 te apparent at first, though the finger as a rule is able to detect it. The origin of the 



