SHEATH OF KECTUS. 



273 



in common with that of the opposite side ; and the external process 

 springs from the pubic crest. Becoming wider towards the thorax, 

 the rectus is inserted by three large fleshy and tendinous slips into 

 the cartilages of the fifth, sixth and seventh ribs, the outermost slip 

 usually extending to the bone of the fifth rib. Some of the inner fibres 

 are often attached to the 

 ensifonn process. 



The muscle is con- 

 tained in an aponeu- 

 rotic sheath, except 

 above and below; and 

 its fibres are interrupted 

 at intervals by tendi- 

 nous lines the inscrip- 

 tiones tendinece. 



Action. It will draw 

 down the thorax and 

 the ribs, or raise the 

 pelvis, according as its 

 fixed point may be below 

 or above. Besides im- 

 parting movement to 

 the trunk, it will 

 diminish the cavity of 

 the abdomen, and com- 

 press the viscera. 



Sheath of the rectus (D). 

 This sheath is derived 

 from the splitting of 

 the aponeurosis of the 

 internal oblique at the 

 outer edge of the rectus. 

 One piece passes before, 

 and the other behind 

 the muscle ; and the 

 two unite at the inner 

 border so as to com- 

 plete the sheath. In- 



insertion 

 into rib- 

 cartilages ; 



has cross 

 tendons ; 



use on 

 tiunk, 



on abdomen. 



Its sheath : 



Conjoined tendon. 



FIG. 



102. THE RECTUS MUSCLE 

 ABDOMEN. 



OP THE how formed 



The muscle is dissected on the right side, and 

 left in its sheath on the left. Close above the 

 pubes the pyramidalis is exposed. 



A. Rectus. 



B. Internal oblique. 



c. Poupart's ligament. 



D. Anterior layer of the sheath of the rectus. 



separably blended with 

 the stratum in front of 

 the rectus is the aponeu- 

 rosis of the external oblique ; and joined in a similar manner 

 with that behind is the aponeurosis of the transversalis. The 

 anterior layer of the sheath adheres closely to the tendinous inter- 

 sections of the muscle. 



The sheath is deficient behind, both at the upper and lower end 

 of the muscle. Above, the muscle rests on the ribs, without the 

 intervention of the sheath, which is fixed to the margin of the 

 thorax. Below, at, or somewhat above, a point midway between the 



D.A. T 



deficient 

 above and 

 below. 



