416 



MYOLOGY 



fifth rib, usually has some fibers of insertion into the anterior extremity of the rib 

 itself. Some fibers are occasionally connected with the costoxiphoid ligaments, 

 and the side of the xiphoid process. 



The Rectus is crossed by fibrous bands, three in number, which are named the 

 tendinous inscriptions; one is usually situated opposite the umbilicus, one at the 

 extremity of the xiphoid process, and the third about midway between the xiphoid 

 process and the umbilicus. These inscriptions pass transversely or obliquely 

 across the muscle in a zigzag course; they rarely extend completely through its 

 substance and may pass only halfway across it; they are intimately adherent in 

 front to the sheath of the muscle. Sometimes one or two additional inscriptions, 

 generally incomplete, are present below the umbilicus. 



Linea 

 semicircularis 



Transverse 



Reetus 

 abdominis 



Inferior epigastric 

 artery and vein 





Obliquus 

 internus 



Inguinal aponeurotic falx Interjoveolar ligament 



FIG. 398. The interfoveolar ligament, seen from in front. (Modified from Braune.) 



The Rectus is enclosed in a sheath (Fig. 399) formed by the aponeuroses of the 

 Obliqui and Transversus, which are arranged in the following manner. At the lateral 

 margin of the Rectus, the aponeurosis of the Obliquus internus divides into two 

 lamellse, one of which passes in front of the Rectus, blending with the aponeurosis 

 of the Obliquus externus, the other, behind it, blending with the aponeurosis of 

 the Transversus, and these, joining again at the medial border of the Rectus, 

 are inserted into the linea alba. This arrangement of the aponeurosis exists from 

 the costal margin to midway between the umbilicus and symphysis pubis, where 

 the posterior wall of the sheath ends in a thin curved margin, the linea semicircu- 

 laris, the concavity of which is directed downward : below this level the aponeuroses 

 of all three muscles pass in front of the Rectus. The Rectus, in the situation where 

 its sheath is deficient below, is separated from the peritoneum by the transversalis 

 fascia (Fig. 400). Since the tendons of the Obliquus internus and Transversus 

 only reach as high as the costal margin, it follows that above this level the sheath 

 of the Rectus is deficient behind, the muscle resting directly on the cartilages of 

 the ribs, and being covered merely by the tendon of the Obliquus externus. 



The Pyramidalis (Fig. 397) is a small triangular muscle, placed at the lower 

 part of the abdomen, in front of the Rectus, and contained in the sheath of that 



