EXTERNAL OR OBLIQUE HERNIA. 421 



exact extent outwards. The fascia transversalis and the spermatic cord 

 should be likewise nicely cleaned. 



Crossing the interval apparent below the border of the transversalis 

 muscle, are the epigastric vessels, which lie close to the inner side of the 

 internal abdominal opening, but beneath the fascia transversalis. A small 

 piece of the fascia may be cut out to show the vessels. 



INGUINAL HERNIA. A protrusion of intestine thorough the lower part 

 of the abdominal wall near Poupart's ligament (the part answering to the 

 inguinal region), is named an inguinal hernia. The escape of the intes- 

 tine in this region is predisposed to by the deficiencies in the muscular 

 strata, by the passage of the spermatic cord through the abdominal 

 parietes, and by the existence of fossae on the inner surface of the wall. 



The gut in leaving the abdomen either passes through the internal ab- 

 dominal ring with the cord, or is projected througli the part of the abdom- 

 inal wall between the epigastric artery and the edge of the, rectus muscle. 

 These two kinds of hernia are distinguished by the names external and 

 internal, from their position to the epigastric artery; or they are called 

 oblique and direct, from the direction they take through the abdominal 

 wall. Thus, the hernia protruding through the internal abdominal ring 

 with the cord is called external from being outside the artery, and oblique 

 from its slanting course ; whilst the hernia between the edge of the rectus 

 and the epigastric artery is named internal from being inside the artery, 

 and direct from its straight course. 



EXTERNAL or OBLIQUE INGUINAL HERNIA leaves the cavity of the 

 abdomen with the spermatic cord, and traversing the inguinal canal, makes 

 its exit from that passage by the external abdominal ring. 



Anatomy of the external hernia. To acquire a knowledge of the anatomy 

 of this hernia it will be necessary that the space in which it lies (inguinal 

 canal), the apertures by which it enters and leaves the wall of the abdo- 

 men (abdominal rings), and the coverings it receives in its progress to the 

 surface of the body, should be studied. 



The inguinal canal (fig. 140) is the interval between the flat muscles 

 of the abdominal wall, which contains the spermatic cord in the male, 

 and the round ligament in the female. Its direction is oblique down- 

 wards and inwards, being nearly parallel to, but above Poupart's ligament; 

 and its length is about one inch and a half. Superiorly it ceases at the in- 

 ternal abdominal ring ; and inferiorly it ends in the external abdominal 

 ring. 



Towards the surface of the body the canal is bounded by the teguments, 

 and the two oblique muscles in this way : The skin with the subjacent 

 fatty layer, and the aponeurosis of the external oblique, A, reach the 

 whole length of the passage ; but the internal oblique, B, extends only 

 along its outer third (half an inch). 



Towards the cavity of the abdomen the wall of the canal is constructed 

 by the conjoined tendon of the internal oblique and transversalis, and by 

 the deep membranous strata in the wall of the abdomen in this wise : 

 The conjoined tendon, H, placed in front of the other structures, reaches 

 along the inner two-thirds of the space (about an inch) ; and beneath or 

 behind it come the fascia transversalis, G, the subperitoneal fat, and the 

 peritoneum, in the order mentioned, which are continued all along the 

 passage. 



Along the lower part, or the floor, the canal is limited by the union of 

 the fascia transversalis with Poupart's ligament, and by the fibres of the 



