254 ABDOMEN 



pubes. Make the incision a little on one side of the middle 

 umbilical ligament, and, when approaching the pubic symphysis, 

 be careful not to injure the urinary bladder, which may project 

 upwards above the symphysis. When the left flap is thrown 

 downwards and laterally, it may be possible to detect the position 

 of the abdominal inguinal ring, from the fact that in some cases 

 the peritoneum is slightly dimpled into it. Now strip the peri- 

 toneum from the flap as far down as the inguinal ligament. 

 That can be easily done with the fingers, as the connection of 

 the peritoneum with the extra-peritoneal fatty tissue is very 

 slight. Next, separate the extra-peritoneal fatty tissue from the 

 fascia transversalis with the handle of the knife, proceeding 

 with great care as the inguinal ligament is approached. The 

 abdominal inguinal ring, or the inlet of the inguinal canal, is 

 now seen from within. From that point of view the opening 

 is more like a vertical slit in the fascia transversalis than a ring. 

 Its lower and lateral margin will be seen to be specially strong 

 and thick. Note the inferior epigastric artery passing upwards 

 and medially, close to its medial, margin. Further, observe the 

 ductus deferens and the spermatic vessels entering it ; the former, 

 as it disappears into the canal, hooks round the inferior epigastric 

 artery. Introduce the tip of the little finger into the opening 

 and push it gently along the line of the inguinal canal. Whilst 

 the finger is still in the opening raise the flap of the abdominal 

 wall and look at it from the front, a very striking demonstration 

 of the internal spermatic fascia will then be obtained. 



If the dissection is satisfactorily completed the student will 

 be able to note that the canal possesses (i) an inlet, the 

 abdominal inguinal ring; (2) a floor formed laterally by the 

 upper concave aspect of the inguinal ligament and medially 

 by the lacunar ligament (Gimbernati) ; (3) an anterior wall; 

 (4) a posterior wall; (5) an exit, the subcutaneous inguinal 

 ring. A roof can scarcely be said to exist, for the anterior 

 and posterior walls are in contact above, but arching above 

 the lateral part of the canal are the lower borders of the 

 internal oblique and the transversus abdominis. He should 

 note also that there are three portions of the anterior wall 

 and three portions of the posterior wall. At the medial 

 end of the anterior wall lies the subcutaneous inguinal 

 ring, covered, and to a certain extent closed, by the inter- 

 crural fibres descending on the spermatic cord. Immediately 

 to the lateral side of the subcutaneous ring the anterior 

 wall is formed by the aponeurosis of the external oblique 

 only, and at its lateral end the anterior wall is composed 

 of the external oblique aponeurosis and the lower fibres of 

 the internal oblique muscle : the anterior wall, therefore, 

 is weakest at its medial and strongest at its lateral ex- 

 teemity. The posterior wall, on the contrary, is strongest 



