THE ABDOMEN 



677 



triangle, the conjoined tendon, and the external abdominal ring. 

 The middle inguinal fossa is situated between the plica hypo- 

 gastrica and plica epigastrica, and lies behind the outer third 



Umbilictis 



Plica Urachi 



Plica Hypogastrica 



Plica Epigastrica 



External Inguinal 

 Fossa 



Anterior Crural 

 Nerve 



Bladder 



External Iliac 

 Artery 



External Iliac Vein 

 Middle Inguinal Fossa 



Fig. 293 



Internal Inguinal Fossa 



. — The Plic.e and Fossae on the Posterior Surface of 

 THE Anterior Abdominal Wall. 



of Hesselbach's triangle. The external inguinal fossa is situated 

 on the outer side of the plica epigastrica, and its lower and inner 

 part is behind the internal abdominal ring. 



INGUINAL HERNIA. 



By an inguinal hernia is meant a protrusion of a viscus (usually bowel, 

 or, it may be, great omentum) from the abdominal cavity in the inguinal region. 

 This region is predisposed to such an occurrence from the presence of the 

 two abdominal rings and inguinal canal, and the inguinal fossae. All forms 

 of inguinal hernia, if complete, ultimately protrude through the external 

 abdominal ring, and thereafter enter the scrotum. Relatively to the deep 

 epigastric artery there are two varieties of inguinal hernia, namely, external 

 and internal, the former leaving the abdominal cavity external to that vessel, 

 and the latter escaping internal to it. Inasmuch, however, as the region 

 inside the deep epigastric artery, namely, Hesselbach's triangle, is divisible 

 into an inner two-thirds and an outer third, there may be two forms of internal 

 hernia. Viewing, therefore, inguinal hernia in its relation to the abdominal 

 wall, there are three varieties, namely, external oblique, internal direct, and 

 internal oblique. 



External Oblique Inguinal Hernia. This variety is called external because 

 the hernia, as it leaves the abdominal cavity, is external to the deep 

 epigastric artery, and oblique, from its oblique course. The course of the 

 hernia is as follows : it enters the external inguinal fossa, and elongates 



