422 ABDOMEN 



narrow but frequently very deep, lies between the fold containing the 

 obliterated part of the umbilical artery and that containing the inferior 

 epigastric artery. It is behind that part of the posterior wall of the inguinal 

 canal which is formed by the transversalis fascia only. The lateral inguinal 

 fossa lies to the lateral side of the fold formed by the inferior epigastric 

 artery and its lowest, medial, and deepest part corresponds with the 

 abdominal inguinal ring. 



Having determined these points, the dissector can proceed as follows : 

 Divide the lower part of the abdominal wall in a vertical direction along the 

 linea alba, from the umbilicus to the pubes. Make this incision a little on 

 one side of the urachus, and, on nearing the pubic symphysis, be careful not 

 to injure the bladder, which may project upwards beyond it. On throwing 

 the left flap 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 peritoneum from the 

 flap as far down as the inguinal ligament. This can be easily done with the 

 fingers, as its connection 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 this 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, hooking round 

 the inferior epigastric artery. Introduce the tip of the little finger into the 

 opening and push it gently downwards in the direction of the inguinal 

 canal. On raising the flap of the abdominal wall and looking at its front 

 aspect, a very striking demonstration of the infundibuliform fascia can thus 

 be obtained. 



When the dissection is satisfactorily completed the student should note 

 that there are three portions of each wall of the canal. At the medial end 

 of the anterior wall lies the subcutaneous inguinal ring covered, and to a 

 certain extent closed, by the intercrural fibres descending on the spermatic 

 cord. Immediately to the lateral side of the superficial 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 extremity. 

 The posterior wall on the contrary is strongest at its medial and weakest 

 at its lateral end. At its medial end, behind the subcutaneous inguinal 

 ring, it is three layers thick, the layers from before backwards being the 

 Jig. inguinale reflexum, the falx inguinalis, and the transversalis fascia. 

 More laterally, opposite the region where the anterior wall consists of external 

 oblique aponeurosis alone, the posterior wall is formed by the transversalis 

 fascia and the falx inguinalis, and still more laterally, where the anterior 

 wall is formed by both external oblique aponeurosis and internal oblique 

 muscle, the posterior wall is represented by transversalis fascia only. The 

 walls of the canal are well adapted, therefore, to resist the effects of intra- 

 abdominal pressure. The student must remember, however, that, for 

 practical purposes, in association with the formation of hernia, the contents 

 of the abdomen may be looked upon as being of a fluid or semifluid nature, 

 consequently if a portion of the abdominal contents happens to slip through 

 the abdominal inguinal ring, into a persisting though shrunken processus 

 vaginalis, the action of the abdominal pressure will, thenceforth, tend to 



