302 THE MUSCLES. 



ring — a necessary complement of the great oblique muscle — will be given here* 

 after. 



Relations of the Great Oblique Muscle. — Externally, to the pectoralis magnus 

 and the abdominal tunic, which latter separates it from the skin and the panni- 

 culus. By its deep face, it is related to the ribs, into which it is inserted, as 

 well as with their cartilages, the corresponding intercostal muscles, the small 

 oblique, and the rectus abdominis. The latter even appears to be attached, 

 through the anterior moiety of its external border, to the fleshy portion of the 

 great oblique, by means of a sHght layer of yellow elastic tissue, which covers, 

 to a small extent, the deep face of the two muscles. 



Action. — The external oblique, in contracting, compresses the abdominal 

 viscera, flexes the vertebral spine, and acts as an expiratory muscle. (By its 

 compression on the abdominal viscera, it concurs in the acts of defecation, 

 micturation, and parturition.) 



Internal Crural Aponeurosis. — This fibrous layer descends from the 

 plicature of the flank on to the patella and the inner surface of the leg. Out- 

 wardly, it is confounded with the aponeurosis of the fascia lata ; inwardly, it 

 degenerates into connective tissue. It covers the long adductor of the leg, part 

 of the short adductor, the vastus internus, and the crural vessels at their exit 

 from the abdominal cavity. 



Crural Arch. — As already mentioned, this is the reflected layer of the 

 great oblique aponeurosis, and is also named the ligament of FaUopius and 

 Poiqxtrfs ligament. It is a wide, flat band, attached by its extremities to the 

 external angle of the ilium and the anterior border of the pubis. Its anterior 

 face (Fig. 165, b) forms, inwardly, the posterior wall of the inguinal canal ; it 

 gives attachment, outwardly, to the posterior fibres of the small oblique muscle. 

 Its posterior face, applied against the superior extremity of the patellar muscles, 

 the long adductor of the leg, the pectineus, and the crural vessels on their 

 leaving the abdomen, embraces all these parts as in a vast arch, and from this 

 peculiarity it derives its name. Its superior border is inserted, for its external 

 half, into the lumbo-iliac aponeurosis. In its middle part it is much thinner, 

 and is prolonged to the external surface of the long adductor muscle of the leg 

 and the iliac fascia, to be at last mixed up with the latter. Within the pectineal 

 insertion of the small psoas muscle, it forms the anterior margin of the crural 

 ring : a triangular orifice circumscribed on the other side by the anterior border 

 of the pubis, the iliacus, and the long adductor of the leg, and through which 

 pass the crural vessels as they leave the abdomen by the crural arch.^ The 

 inferior border is continuous with the femoral aponeurosis and that of the great 

 oblique muscle. 



Inguinal Canal. — This is an infundibuliform canal, compressed laterally, 

 through which the spermatic cord and external pudic artery pass from the 

 abdomen in the male, and the external mammary vessels in the female. 



Situated on the side of the prepubic region, in an oblique direction do^vn- 

 wards, backwards, and inwards, and measuring from two to two and a half inches 

 in length, this canal lies between the crural arch, which constitutes its posterior 



' This orifice is covered by a very thin aponeurotic layer, which is prolonged, above, on 

 the crural vessels, behind, into the pelvic cavity, and which appears to be continuous, inferiorly, 

 with the upper border of Poupart's ligament. This layer is perhaps only a dependency of the 

 subperitoneal aponeurosis ; and if so, it represents the only vestige of the fascia transversalis 

 It has been possible to discover in Solipeds. 



