SUPERFICIAL MUSCLES. 83 



attachments of the annular ligament, but not within the arch of 

 that band ; here it is hound down by a fibrous sheath and is 

 lined by a synovial membrane. The tendon is inserted into the 

 base of the nietacarpal bone of the index finger, and sends a slip 

 to that of the middle digit. 



SECTION YT. 



THE BACK OF THE FOREARM. 



Position. During the dissection of the hack of the forearm the Position, 

 limb lies on the front, and a small block is to be placed beneath 

 the wrist, for the purpose of stretching the tendons. 



Dissection (fig. 35). The fascia and the cutaneous nerves and Takeaway 

 Is are to be reflected from the muscles of the forearm, and from ficialnen'es 

 the tendons on the back of the hand ; but in removing the fascia 

 in the forearm, the student must be careful not to cut away the 

 rior interosseous vessels, which are in contact with it on the 

 ulnar side in the lower third. A thickened l.iand of the fascia 

 opposite the carpus (the posterior annular ligament) is to be left. 



Let the integument be removed from the fingers, in order that strip 

 the tendons may be traced to the end of the digits. 



The several muscles should be separated from one another up to Separate 

 their origin, especially the two radial extensors of the wrist. 



The POSTERIOR ANNULAR LIGAMENT (K) IS a part of the deep Annular 



fascia, thickened by the addition of transverse fibres, and is situate behind the 

 opposite the lower ends of the bones of the forearm. This l>and is wrist - 

 attached on the outer side to the radius, and on the inner side to the 

 pyramidal and pisiform bones. Processes from it are fixed to the 

 Dorics beneath, and confine the extensor tendons. The ligament 

 will subsequently be examined more in detail. 



SUPERFICIAL LATER OF MUSCLES (fig. 35). The muscles of the Superficial 

 back of the forearm are arranged in a superficial and a deep layer. S even 

 The superficial layer contains seven muscles, which arise, in part by muscles, 

 a common tendon, from the outer side of the hunierus, and are 

 placed in the following order from without inwards : the long 

 supinator (A), the long and short radial extensors of the wrist (B 

 and c), the common extensor of the fingers (D), the extensor of the 

 little finger (E), and the ulnar extensor of the wrist (F). There is 

 one other small muscle near the elbow the anconeus (G). 



The SUPINATOR RADII LONGUS (A) reaches upwards into the arm, supinator 

 and limits on the outer side the hollow in front of the elbow. It lo 



> from the upper two-thirds of the external supracondylar ridge ongm 

 of the humerus, and from the front of the external intermuscular 

 septum of the arm. The fleshy fibres end about the middle of the 

 forearm in a tendon, which is inserted into the lower end of the insertion ; 

 radius, close above the styloid process. 



In the arm the margins of the supinator are directed towards the relations ; 

 surface and the bone, but in the forearm the muscle is flattened over 



G2 



