316 MUSCLES OF THE ABDOMEN. 



surface of the eight inferior ribs, by slips arranged in a serrated series, 

 four or five of them meeting with origins of the serratus magnus, and 

 three or four with origins of the latissimus dorsi. The shps of these 

 two sets of muscles alternate with each other, as the tips of the fingers 

 of one hand may be made to fit in between those of the other, and 

 hence they are said to interdigitate, and are termed digitations. The 

 lower and upper digitations of the external oblique are connected with 

 the I'ibs near their cartilages, the others are attached to the ribs at 

 some distance from their extremities ; the lowest digitation generally 

 embraces the point of the twelfth rib. The ficshy fibres from the last 

 ribs pass down in nearly a vertical direction to be inserted into the ex- 

 ternal margin of the crest of the ilium for about the anterior half of 

 its length ; all the rest incline downwards and forwards, and terminate 

 in tendinous fibres, which form the broad aponeurosis by which the 

 muscle is inserted. 



The aponeurosis of the external oblique muscle, Avider at the lower 

 than at the upper part, and larger than that of either of the subjacent 

 abdominal muscles, extends inwards towards the middle line in front ; 

 at some distance from this, but farther out above than below, it becomes 

 inseparably united with the aponeurosis beneath, and forms a part of 

 the sheath of the rectus muscle in the whole extent of the space from 

 the ensiform cartilage to the symphysis pubis. The upper part of the 

 aponeurosis is connected externally with the larger pectoral muscle. 

 Its lower fibres are closely aggregated together, and extend across from 

 the anterior superior iliac spine to the spine of the pubis, in the form 

 of a broad band, which is called PovyarVs ligament. This band is curved 

 at the middle and outer parts, the convexity of the curve being directed 

 towards the thigh, a form which is given to it by its connection with 

 the foscia lata of the limb. 



Above the crest of the pubis the fibres of the aponeurosis, separating 

 from the inner part of Poupart's ligament, leave between tiiem an 

 oblique opening, the siiporjicial or external abdominal ring, through 

 which passes the spermatic cord in the male and the round liga- 

 ment in the female. The direction of this opening is upwards and 

 outwards, its base being formed by the pubic crest, and its sides by the 

 two sets of diverging fibres called the pillars. The upper or internal 

 pillar is attached to the anterior surface of the symphysis pubis, inter- 

 lacing with the corresponding fibi"es of the opposite side ; the lower 

 or external pillar is formed by Poupart's ligament, near its attach- 

 ment to the spine of the pubic bone. The inner pillar is flat and 

 straight, but the outer, especially near its attachment to the pubis, is 

 thick and triangular. The innermost fibres of the outer pillar are 

 continued over the crest of the pubis and beneath the spermatic cord 

 in a thin somewhat fan-shaped layer called the triangntar fascia, which, 

 curving upwards and inwards, passes behind the base of the inner 

 pillar to interlace with the fibres of the opposite side. 



A portion of the aponeurosis, which is reflected backwards and out- 

 wards along the pectineal line from the attachment of Poupart's liga- 

 ment to the spine of the pubis, constitutes a small triangular process 

 with a curved external boixler, not far distant from the femoral ring. 

 This receives the name of Gimhernafs ligament. Some curved fibres, 

 directed across the diverging pillars and uniting them together, are 

 named inter columnar. A few of these, descending upon the spermatic 



