212 MUSCLES OF THE ABDOMEN. 



line, from over the lower part of the sternum to the pubes ; the 

 second, oblique, from the umbilicus, upwards and outwards, to the 

 outer side of the chest, as high as the fifth or sixth rib ; and the third, 

 oblique, from the umbilicus, downwards and outwards, to the middle 

 of the crest of the ilium. The three flaps included by these incisions 

 should then be dissected back in the direction of the fibres of the ex- 

 ternal oblique muscle, beginning at the angle of each. The integu- 

 ment and superficial fascia should be dissected off together so as to ex- 

 pose the fibres of the muscle at once. 



If the external oblique muscle be dissected on both sides, a white 

 tendinous line will be seen along the middle of the abdomen, extend- 

 ing from the ensiform cartilage to the os pubis ; this is the linea alba. 

 A little external to it, on each side, two curved lines will be observed 

 extending from the sides of the chest to the os pubis, and bounding 

 the recti muscles : these are the lines semilunares. Some transverse 

 lines, linear transverse, three or four in number, connect the linese 

 semilunares with the linea alba. 



The EXTERNAL OBLIQUE MUSCLE (obliquus externus abdominis 

 descendens) is the external flat muscle of the abdomen. Its name is 

 derived from the obliquity of its direction, and the descending course of 

 its fibres. It arises by fleshy digitations from the external surface of 

 the eight inferior ribs ; the five upper digitations being received be- 

 tween corresponding processes of the serratus magnus, and the three 

 lower of the latissimus dorsi. Soon after its origin it spreads out 

 into a broad aponeurosis, which is inserted into the outer lip of the 

 crest of the ilium for one half its length, the anterior superior spinous 

 process of the ilium, spine of the os pubis, pectineal line, front of the 

 os pubis, and linea alba, 



The lower border of the aponeurosis, which is stretched between 

 the anterior superior spinous process of the ilium and the spine of the 

 os pubis, is rounded from being folded inwards, and forms PouparCs 

 ligament; the insertion into the pectineal line is Gimbernafs ligament. 



Just above the crest of the os pubis is the external abdominal ring, a 

 triangular opening formed by the separation of the fibres of the apo- 

 neurosis of the external oblique. It is oblique in its direction, and 

 corresponds with the course of the fibres of the aponeurosis. It is 

 bounded below by the crest of the os pubis ; on either side, by the borders 

 of the aponeurosis, which are called/n^ars; and above by some curved 

 fibres (inter-columnar}, which originate from Poupart's ligament, and 

 cross the upper angle of the ring, so as to give it strength. The external 

 pillar, which is at the same time inferior from the obliquity of the 

 opening, is inserted into the spine of the os pubis ; the internal or supe- 

 rior pillar forms an interlacement with its fellow of the opposite side 

 over the front of the symphysis pubis. The external abdominal ring 

 gives passage to the spermatic cord in the male, and round ligament in 

 the female: they are both invested in their passage through it by a 

 thin fascia derived from the edges of the ring, and called inter-columnar 

 fascia, or fascia spermatica. 



