210 ABDOMEN 



circular, but triangular, in shape. The long axis of the 

 opening is very oblique, the base of the triangle being formed 

 by the crest of the pubis, whilst the apex is directed laterally 

 and slightly upwards. 



The subcutaneous inguinal ring, therefore, is merely a small 

 gap or interval left between that portion of the aponeurosis 

 of the external oblique muscle which forms the inguinal 

 ligament, and that portion which is inserted into the front of 

 the pubic bone. The margins of the aperture are termed 

 the crura of the ring. The superior crus is flat and broad, 

 and is attached to the body of the pubis. Some of its 

 fibres cross the median plane, decussate with the corre- 

 sponding fibres of the other side, and are inserted into the 

 front of the opposite pubic bone. The inferior crus is 

 merely 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 inferior crus. 



The size of the subcutaneous inguinal ring is very variable. 

 In the male, the average length may be said to be 25 mm. 

 (one inch), and the breadth about 12.5 mm. (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 

 oblique aponeurosis, the student will see a number of cross 

 fibres arching over its surface. They are called the 

 intercrural fibres, 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 the intercrural fibres is very evident, and the 

 term "intercrural" is derived from the part which they play. 

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

 their further separation. There is a direct continuity between 

 the intercrural fibres and the external spermatic fascia which 

 clothes the spermatic cord. 



Dissection. 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 



