THE FASCIA AND MUSCLES' OF THE ABDOMEN 185 



2. M. pyramidalis rests on the lower part of the rectus inside 

 its sheath, separated from it by a special fascia. Origin, front 

 of the pubis below the insertion of the outer tendon of the 

 rectus, passes over the lower third of the space between the 

 umbilicus and pubis; inserted into the linea alba. Its inner 

 fibers are vertical, outer ones oblique. 



The linea alba is a fibrous structure from the ensiform to 

 the pubis, formed by the union of the oblique and transverse 

 aponeuroses, broadest above, i- inch (4 to 7 mm.), and a little 

 below its middle is the cicatrix of the umbilicus. At the lower 

 end it passes in front of the recti, and here is detached pos- 

 teriorly a band of longitudinal fibers = adiminiculum linece 

 albce, spreading out triangularly behind the outer heads of 

 the recti. 



The linea semilunaris is a depression seen on the outer side 

 of each rectus abdominis muscle, and corresponds to the line 

 of fusion of the aponeuroses of the oblique and transversalis 

 muscles, as they blend to pass in front and behind the recti 

 muscles to form the sheath of the latter muscles. It extends 

 from opposite the ninth costal cartilage to the spine of the 

 pubic bone. 



Lineae transversse are depressions seen along the recti muscles, 

 and correspond to the attachment of the aponeuroses of the 

 abdominal muscles to the rectus. They are usually three 

 one below the ensiform cartilage, one between the ensiform and 

 the umbilicus, and one opposite or below the umbilicus. 



1. M. obliquus externus, or descending oblique, is muscular 

 on the side, aponeurotic in front. Origin, outer surfaces and 

 lower borders of the lower eight ribs (seven, Henle) by slips 

 in a serrated series, five interdigitating with the serratus mag- 

 nus, the lower three with the latissimus dorsi, from the lumbo- 

 dorsal aponeurosis connected with first lumbar vertebrae. The 

 slip from the eighth rib is broadest, the others diminish above 

 and below that; upper and lower digitations rise from near 

 the costal cartilages, the intermediate ones at some distance 

 from them. 



The fibers from the last two ribs pass nearly vertically down 

 to insert the anterior half of the outer lip of the iliac crest; 

 all the rest incline down and forward to the aponeurosis. This 

 is wider below than above, meets its fellow in the linea alba, 

 is connected with the costoxiphoid ligament, gives origin to 



