388 ABDOMEN 



corresponding fibres of the other side, and are inserted into 

 the front of the opposite pubic bone. The lateral or inferior 

 cms is simply the medial end of the inguinal ligament. It 

 is, therefore, thick and strong, and is fixed to the pubic 

 tubercle. The spermatic cord, as it issues from the sub- 

 cutaneous inguinal ring, rests upon the lateral crus. 



The size of the subcutaneous inguinal ring is very variable. 

 In the male the average length may be said to be one inch, 

 and the breadth about half an inch. In the female it is 

 much smaller, and the round ligament of the uterus which 

 passes through it ends in the superficial fascia of the groin. 



On a close inspection of the lower part of the external 

 abdominal aponeurosis, the student will observe a number of 

 cross fibres arching over its surface. These are called the 

 fibrae intercrurales, and in some cases they are very strongly 

 marked. They begin at the inguinal ligament, close to the 

 iliac spine, and curve upwards and medially, upon the 

 aponeurosis, above the subcutaneous inguinal ring. The 

 function of these fibres is very evident, and the term " inter- 

 crural" is derived from the part which they play. They 

 bind together the two crura of the ring, and prevent their 

 further separation or divarication. There is a direct con- 

 tinuity between the intercrural fibres and the external 

 spermatic fascia which clothes the cord, and consequently, 

 as already stated, the term " intercrural " is frequently applied 

 to the latter. 



Reflection of the Obliquus Externus. Between the last rib and the 

 crest of the ilium the posterior border of the external oblique muscle is 

 free, and as this border will be examined when the body is placed on its 

 face it must not be disturbed at present. Begin by detaching the upper 

 six serrations of the muscle from the ribs ; from the interval between the 

 sixth and seventh serrations carry an incision downwards, through the 

 fibres of the muscle, to the posterior border of the tubercle on the lateral 

 lip of the iliac crest. Raise the anterior portion of the muscle from the 

 surface of the subjacent internal oblique and turn it medially, dividing the 

 fleshy fibres inserted into the iliac crest close to the bone. Next divide 

 the aponeurosis horizontally, in a line leading from the anterior superior 

 spine to the lateral border of the rectus. The greater part of the muscular 

 and aponeurotic portion of the external oblique can now be thrown 

 medially. The dissector must proceed with care on approaching the 

 lateral border of the rectus, because a little beyond this the anterior lamella 

 of the aponeurosis of the internal oblique fuses with the deep surface of 

 the aponeurosis of the external oblique. Define the line of union, and 

 notice that it does not extend beyond the lower margin of the thorax. 

 Above this the rectus is simply covered by the aponeurosis of the external 

 oblique ; its outer margin in this locality is bare, and the hand can be. 

 freely passed between it and the costal cartilages. 



