HERNIA 421 



moreover, the constituent parts of the anterior and posterior 

 walls are so arranged that weakness of one wall is compen- 

 sated for by strength in the opposite wall. The dissector 

 should now proceed to demonstrate the truth of these state- 

 ments by making a special dissection of the inguinal region on 

 the left side of the body, which has been kept intact for the 

 purpose. 



Dissection. Begin by reflecting the aponeurosis of the external oblique. 

 Make a vertical incision through it, parallel to the lateral border of the 

 rectus, and carry the incision downwards on the medial side of the medial 

 crus of the subcutaneous inguinal ring. The aponeurosis can thus be thrown 

 downwards and laterally and, at the same time,- the subcutaneous ring 

 is preserved. The internal oblique, cremaster, and falx inguinalis should 

 now be cleaned, and their precise relations to the spermatic cord studied. 

 Notice that the fleshy lower border of the internal oblique overlaps the 

 upper part of the cord, whilst, towards the outlet of the inguinal canal, 

 the falx inguinalis lies behind the cord. Next replace the aponeurosis of the 

 external oblique, and introduce the point of the forefinger into the sub- 

 cutaneous ring and press directly backwards. Observe that the finger rests 

 upon either the lig. inguinale reflexum which lies anterior to the falx in- 

 guinalis, or, if the reflex inguinal ligament is absent, upon the falx inguinalis 

 itself; that, in fact, this fascia and tendon and the fascia transversalis inter- 

 vene between the finger and the extra-peritoneal fatty tissue and the 

 peritoneum. The lower part of the internal oblique muscle should now 

 be separated from the transversalis by insinuating the handle of the knife 

 between them. When this is done, divide the internal oblique close to 

 the inguinal ligament, and throw it medially. At the same time, make 

 a longitudinal incision through the cremaster muscle, and turn it aside 

 from the surface of the cord. 



All further dissection must be effected from the inside. Divide the 

 abdominal wall horizontally, from side to side, at the level of the umbilicus. 

 On raising the lower part and examining its posterior aspect three peritoneal 

 folds are seen, the plica timbilicales, a median and two lateral. In the 

 median fold lies the urachus, which descends from the umbilicus to the apex 

 of the bladder, and in each lateral fold is the obliterated portion of the 

 umbilicaj branch of the hypogastric artery of the corresponding side. Each 

 lateral fold, with the contained obliterated artery, descends from the um- 

 bilicus to the side of the bladder if the latter is distended, and to the lateral 

 wall of the pelvis if the bladder is empty. The lower part of the fold lies 

 on the posterior surface of the abdominal wall, a short distance to the . 

 medial side of the abdominal inguinal ring. There is still another fold 

 on each side of the posterior aspect of the abdominal wall, caused by the 

 inferior epigastric artery as it ascends to the posterior aspect of the rectus 

 abdominis ; it is placed at a short distance to the lateral side of the lateral 

 umbilical fold, but runs more or less parallel with it. 



By means of these folds three fossae are mapped out on each side of the 

 middle line above the inguinal ligament ; they are termed the supravesical, 

 the medial, and lateral inguinal fossre, and are regarded as determining, to 

 some extent, hernial protrusions in the inguinal region. The supravesical 

 fossa lies between the fold enclosing the urachus and that enclosing the 

 obliterated part of the umbilical artery, and the subcutaneous inguinal 

 ring is in front of its lower part, separated from it by the most medial part 

 of the posterior wall of the inguinal canal. The middle inguinal fossa, 

 127 a 



