EXTERNAL OBLIQUE MUSCLE. 



265 



is in front of a line extended upwards from the anterior end of the 

 iliac crest, and as the dissector approaches that part he must be 

 careful not to injure the tendon, more particularly above, where it 

 lies on the margin of the ribs, and is very indistinct. 



On the left side the external abdominal ring (c) may be defined, 

 to show the spermatic cord passing through it ; but on the right side 

 a thin fascia (intercolimmar), which is connected with the margin 

 of tli at opening, is to be preserved. Lastly, the free border of the 

 external oblique should be made 

 evident between the last rib and the 

 iliac crest. 



MUSCLES OF THE ABDOMINAL 

 WALL. On the side of the abdomen 

 are three large flat muscles, which 

 are named from their position to 

 one another, and from the direc- 

 tion of their fibres : the external 

 oblique; the internal oblique; and 

 the deepest, the transversalis. 



Near the middle line are placed 

 other muscles which have a vertical 

 direction ; namely, the rectus and 

 the pyramidalis ; and behind is the 

 quadratus lumborum : these all are 

 encased by sheaths derived from 

 the aponeuroses of the lateral 

 muscles, and will be subsequently 

 seen. 



The EXTERNAL OBLIQUE MUSOLE 



(fig. 98, A, and fig. 97) is fleshy on 



the side, and aponeurotic on the 



fore part of the abdomen. It arises 



by fleshy processes from the eight 



lower ribs, the five highest pieces 



alternating with similar parts of 



the serratus magnus, and the lowest 



three with slips of the latissimus 



dorsi muscle. From the attachment 



to the ribs the fibres are directed 



over the side of the abdomen to end in the following manner : the 



lower ones descend almost vertically to be inserted into the anterior 



half or more of the outer margin of the iliac crest (fig. 47, p. 113) ; and 



the upper and middle fibres are continued forwards obliquely to the 



tendon or aponeurosis on the front of the belly. 



The aponeurosis occupies the front of the abdomen, internal to 

 a line drawn from the prominence of the ninth rib-cartilage to 

 a point about an inch and a half in front of the anterior superior 

 iliac spine ; and it is broader below than above. Along the middle 

 line it ends in the lima alba the common place of union in the 



To define 



abdominal 



ring. 



the aponeu- 

 roses of 

 which en- 

 case three 

 vertical. 



External 

 oblique 

 muscle : 



origin from 

 ribs; 



FIG. 98. 



A. The external oblique muscle. 



B. Poupart's ligament. 



c. External abdominal ring. 

 D. Gimbernat's ligament. 



insertion 

 into pelvis 

 and linea 

 alba. 



Aponeurosis 

 covers front 

 of the belly ; 



