MUSCLES OF TEE TRUNK. 301 



appendage, this cord is confounded, behind, with a large tendon, the prepvbic or 

 common tendon of the abdominal muscles, which is fixed to the anterior bonier of 

 the pubis (Figs. 140, a ; 176, 10). This tendon, covered bj the abdominal tunic, 

 contributes to form the internal commissure of the inguinal ring, and gives 

 origin to the pubio-femoral ligament. 



Towaids the union of its posterior third with its two anterior thirds, the 

 white line widens, so as to form a lozenge-shaped space, in the centre of which is 

 found the remains of the umbilicus and the umbilical cord (Fig. 147, o). 



3. Great Oblique, or External Oblique of the Abdomen (Obliquus 

 Abdominis Externus) (Figs. 162, 18 ; 176, 1). 



Synonyms. Costo-abdominalis — Girard. 



Situation — Composition. — This muscle, the largest and the most superficial of 

 the four, is situated on the side and floor of the abdomen, and is composed of a 

 fleshy and an aponeurotic portion. 



Form, Structure, and Attachments of the fleshy portion. — This is composed of 

 fibres directed obliquely downwards and backwards, and presents itself as a wide 

 muscular band, narrower before than behind, applied to the inferior surface of 

 the last thirteen or fourteen ribs. Its superior border is concave, and attached : 

 1. To the external surface of the ribs just mentioned by as many slightly 

 aponeurotic digitations, the first four of which cross the dentations of the great 

 serratus. 2. To the aponeurosis of the latissimus dorsi, from the last rib to the 

 external angle of the ilium (Fii;-. 162, 18). Its inferior border, convex and 

 sinuous, is continuous with the aponeurosis -, it descends, in front, to the cartila- 

 ginous circle of the false ribs, which it projects beyond posteriorly, increasing in 

 this as it nears the lumbar region. 



Form, Striu-ture, and Attachments of the Aponeurosis. — This is naiTow and 

 thin in front, wide and thick behind, of a triangular form, and composed of 

 white, nacrous-looking fibres passing in the same direction as the fibres of the 

 fleshy portion, with the inferior border of which it is continuous by its external 

 border. Its internal border is inserted into the white line and the prepubic 

 tendon ; and its posterior border, extending from the external angle of the ilium 

 to the anterior border of the pu])is, i-esponds to the plicature of the flank, 

 embraces the coiTesponding crural muscles, and establishes the hue of demarcation 

 between the trimk and the abdominal limb. 



The aponeurosis of the great oblique gives rise, at its posterior border, to two 

 very remarkable fibrous layers, which appear to be produced by the doubling of 

 this aponeurosis. One of these layers descends on the internal muscles of the 

 thigh to constitute the crurcd aponeurosis (Fig. 176, 4) ; while the other is 

 reflected upwards and forwards, to enter the abdominal cavity. This reflected 

 layer of the great oblique aponeurosis is named the crural arch {ligament of 

 Poupart or Fallopius) (Fig. 165, b). 



Near the prepubic tendon of the abdominal muscles, and immediately before 

 its division into two layers, the aponeurosis of the external oblique is pierced 

 by a large oval aperture (the external abdominal ring) (Fig. 176, 5), the inferior 

 orifice of the canal through which passes the cord of the testicle in the male, 

 and the mammary vessels in the female. This channel has been named the 

 inguimd caned. 



The description of the femoral aponeurosis, the crural arch, and the ingumal 

 22 



