THE VENTRAL MUSCLES. 



525 



Owing to the oblique direction of the canal, that portion of the aponeurosis of 

 the external oblique which is strengthened by the intercolumnar fibres, together with 

 a portion of the internal oblique, forms its anterior wall, while its posterior wall is 

 formed by the aponeurosis of the trans versalis, together with the more medial lower 

 portion of that of the internal oblique, these two layers of fascia uniting in this region 

 to form what is termed the conjoined tendon, which is attached below to the body and 

 superior ramus of the pubis, and medially is especially thickened to form a band, the 

 falx inguinalis, firmly attached along its medial border to the tendon of the rectus. 

 More laterally, where it forms the medial boundary of the internal abdominal ring, it 

 is also thickened (Fig, 531), forming the ligatnent of Hesselbach (ligamentum inter- 

 foveolarej. Between these two thickenings the abdominal wall is weaker (Fig. 1493) 

 and may give way to internal pressure, permitting a hernia, which comes to the sur- 

 face at the external abdominal ring without having traversed the inguinal canal, and is 

 therefore spoken of as a direct hernia, in contradistinction to the more usual oblique 

 hernia which enters the canal at the internal abdominal ring. 



Fig. 531. 



Rectus. 



Deep epigastric artery 



Interfoveolar or 



Hesselbach's ligament 



Weak area 



Conjoined tendon 



Muscular fibres 



Lower end of Pouparf s ligamen 

 Urachus 



Bladder 



Poupart's ligament 



Transversalis muscle 



— Spermatic vessels 

 External iliac artery 

 External iliac vein 



— Deep epigastric artery (cut) 

 \'as deferens 



-Femoral ring 

 Gimbernat's ligament 



Dissection of posterior surface of anterior abdominal wall, showing relations of conjoined tendon and its expansions 



to internal abdominal ring. 



A small fasciculus of muscle-tissue is sometimes found close to the medial border of the 

 internal abdominal ring. It is the ni. interfoveo/afis (Fig. 531), and arises from the superior 

 ramus of the pubis, passing almost directly upward to spread out on the posterior surface of the 

 transversalis. It is generally regarded as an aberrant portion of the transversalis muscle. 



The Posterior Surface of the Anterior Abdominal W^all. — Throughout 

 its entire extent, with the exception of a small area in the median line below, the 

 posterior surface of the anterior abdominal wall is lined by peritoneum. In the 

 exceptional area the peritoneum is kept from actual contact with the wall by a 

 band of fibrous tissue, the urachus, which extends from the apex of the urinary 

 bladder to the umbilicus and supports the peritoneum somewhat in the manner 

 of a ridge-pole of a tent, so that between it and the abdominal wall there is an 

 interval occupied only by loose areolar tissue and termed the prevesical space of 

 Retzius (page 1906). 



Laterally from the urachus a fibrous cord, the lateral ligament of the ^imbilicus, 

 may be seen on each side, passing from the side of the bladder to the umbilicus and 

 representing the obliterated hypogastric arteries of the foetus ; while still more laterally 

 there may be seen coming from the external iliac artery the inferior or deep epigas- 

 tric artery, which, passing immediately to the inner side of the internal abdominal 

 ring and posterior to the interfoveolar ligament (Fig. 532), extends upward and 

 inward to penetrate the posterior layer of the sheath of the rectus a short distance 

 below the level of the umbilicus. Both these structures produce a slight ridging or 

 fold of the peritoneum, that formed by the obliterated hypogastric artery being termed 

 Xh^ plica umbilicalis lateralis, while the other is the plica epigastrica. These two 

 folds, together with the urachus, mark of? the lower portion of the abdominal wall 



