THE ABDOMINAL WALL 227 



its floor, its anterior wall, and its posterior wall have still to 

 be examined. 



The floor of the lateral and deeper part of the canal is 

 formed by the upper grooved surface of the inguinal ligament. 

 Towards the outlet, however, the floor becomes broader and 

 more definite ; there it is formed not only by the inguinal 

 ligament, but also by the lacunar ligament. At that point, 

 as the dissector has previously noted, the cord rests 

 directly upon the abdominal surface of the lacunar ligament. 

 The parts which enter into the formation of the anterior wall 

 are (i) the aponeurosis of the external oblique, throughout 

 the entire extent of the canal ; and (2) the lower border of 

 the internal oblique, in the lateral third of the canal. These 

 facts can be readily verified if the structures are restored 

 to their original positions. The parts which compose the 

 posterior wall are still in situ. Named in order, from the 

 inlet to the outlet, they are (i) the fascia transversalis; 

 (2) the falx inguinalis; and (3) the ligamentum inguinale 

 reflexum, when that structure is developed (Fig. 102). 



But it may be asked, does the transversus abdominis muscle 

 take no part in the formation of the inguinal canal ? The 

 student can readily satisfy himself as to that point. He will 

 notice that the arched lower border of the transversus 

 muscle does not descend so low as the lower border of the 

 internal oblique ; that, in fact, it stops short immediately 

 above the abdominal inguinal ring. Therefore the trans- 

 versus abdominis takes no part in the formation of the 

 anterior wall of the canal. The canal is closed superiorly 

 by the approximation of the anterior and posterior walls, 

 above the cord, and by the intervention between the walls 

 of the lower border of the transversus abdominis. 



There is still another point to be noted, viz., the relation 

 which the inferior epigastric artery bears to the posterior wall 

 of the canal. That vessel can be felt (and, indeed, in most 

 cases seen) extending obliquely upwards and medially, 

 posterior to the transversalis fascia, to the lateral border of the 

 rectus. A triangular area is thus mapped out by the artery, 

 the inguinal ligament, and the lateral border of the rectus. 

 It receives the name of the triangle of Hesselbach. The 

 triangle lies behind the posterior wall of the inguinal canal, 

 and chiefly behind that part of it which is formed by the falx 

 inguinalis (O.T. conjoined tendon), 

 ii 15 



