RECTUS MUSCLE. 



415 



Fig. 139. 



posed. The dissector should leave the nerves entering the outer border of 

 the rectus. 



On the left side of the body the rectus should not be laid bare below 

 the umbilicus, for the sake of the hernia to be seen on this side. 



The RECTUS MUSCLE (fig. 139, A ) extends along the front of the abdo- 

 men from the pelvis to the chest. It is narrowest interiorly, and is at- 

 tached to the pubes by two tendinous processes ; one, internal and the 

 smaller, arises from the front of the symphysis, where it joins the muscle 

 of the opposite side ; and the external process is attached to the pubic 

 crest. Becoming wider towards the thorax, the rectus is inserted by 

 three large fleshy processes into the ensiform cartilage, and the cartilages 

 of the last three true ribs. 



The muscle is contained in an aponeurotic sheath, except above and 

 below ; and its fibres are interrupt- 

 ed at intervals by irregular tendi- 

 nous lines the inscriptiones ten- 

 dineae. 



Action. It will draw down the 

 thorax and the ribs, or raise the 

 pelvis, according as its fixed point 

 may be above or below. Besides 

 imparting movement to the trunk, 

 it will diminish the cavity of the 

 thorax, and compress 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 

 muscle. One piece passes before 

 and the other under the rectus ; 

 and the two unite at the inner 

 border so as to inclose it in a 

 sheath. Inseparably blended with 

 the stratum in front of the rectus is 

 the aponeurosis of the external 

 oblique ; and joined in a similar 

 manner with that behind, is the 

 aponeurosis of the transversalis. 



The sheath is deficient behind, 

 both at the upper, and lower part 

 of the muscle. Above, the muscle 

 rests on the ribs, without the in- 

 tervention of the sheath which is 

 fixed to the margin of the thorax. 

 Below, midway between the um- 

 bilicus and the pubes, the internal 

 oblique ceases to split, and passes 



altogether in front of the rectus, with the other aponeuroses ; at the spot 

 where the sheath is wanting inferiorly the muscle is in contact with the 

 fascia transversalis, and a white semilunar line (the fold of Douglas) may 

 be sometimes seen, when the outer edge is raised, marking the cessation. 



The linece transversce (fig. 137), on the surface of the abdomen, are 

 caused by tendinous intersections of the rectus. They are usually three 



RECTUS MUSCLE OF THE ABDOMEN, dissected on 

 the right side, and in its sheath on the left. 

 Close to the pelvis is the pyramidalis exposed. 



A. Eectus. 



B. Internal oblique. 



c. Poupart's ligament. 

 D. Sheath of the rectus. 



: o 



Ctf 

 O 



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CD 



5 



