THE MUSCULAR SYSTEM 



233 



terminal phalanges. These slips are functionally and probably 

 morphologically the long flexor tendons (ft.), and correspond 

 in a way to the long extensor tendons of the dorsal side, but it 

 must be remembered that here they are the continuation, not 

 of muscular bellies, but of a non-contractile aponeurosis. The' 

 entire aponeurosis, however, is caused to move by serving as 

 point of insertion of several muscles, more proximally placed, 



Ill 



III 



FIG. 63. Muscles of the fore-paw of Necturus; ventral aspect 



(a) Superficial muscles, (b) Deeper muscles. 



fp, palmar fascia; ps, palmaris superficial; pp, palmaris profundus; uc, ulno- 

 carpalis; fu, ulnar flexor; fr, radial flexor; pr, pronator; yy, flexores breves super- 

 ficiales; it, terminal tendons of the palmar fascia. 



the palmaris superficialis (ps), which inserts along its proximal 

 edge, or, more exactly, between its two layers, which thus 

 invest the muscle, and the palmaris profundus (pp), which is 

 entirely covered by the aponeurosis and inserts into its dorsal 

 (internal) side. The action of these muscles upon the aponeu- 

 rosis causes it to act indirectly, through its digital slips, upon 

 the separate digits, and cause a complete flexion. Aside from 

 the palmaris system, the physiological action of which is that 



