1766 



HUMAN ANATOMY. 



{plica urachi) — is divided on each side into two shallow depressions by a slight eleva- 

 tion of the peritoneum over the deep epigastric artery {plica epigastrica) running 

 from a little internal to the middle of Poupart's ligament to a point on the outer 

 edge of the rectus muscle about one-third the distance between the level of the 

 symphysis pubis and that of the umbilicus. The outer of these depressions is called 

 the exteryial inguinal fossa (hernial fossa). The inner contains a triangular space 

 known as Hesselbach's triangle, bounded by the plica epigastrica, the outer edge 

 of the rectus, and Poupart's ligament. The whole inner region — extended to the 

 mid-line — is further subdivided by a line corresponding to the peritoneal fold over 

 the obliterated hypogastric artery {plica hypogastrica) into two other fossae, the 

 internal inguinal and the supravesical^ which are of use as aids to the description 

 of hernia, but, viewed as mechanical factors, have little bearing on its production. 



The external inguinal fossa is deepened just to the outer side of the epigastric 

 artery into a slight pouch (Fig. 1487), which marks the point of exit of the sper- 

 matic cord from the abdomen, and therefore the site of the internal abdominal ring 

 and of the mouth of one form of inguinal hernia, — the external, oblique, or indirect. 

 On the external surface of the abdomen this pouch corresponds to an area about three- 

 quarters of an inch in circumference, situated a finger' s-breadth above the middle of 

 Poupart's ligament. To the inner side of the epigastric artery are two other and 



Fig. 1487. 



Peritoneal surface 



Plica epigastrica —i 

 Hesselbach's triangle _!. 



Vas deferens 



External iliac artery— l- 

 External iliac vein 



Plica hypogastrica 



-/ 



-J — Outer edge of rectus 

 \ muscle 



Supravesical fossa 



— Outer inguinal fossa 

 -^ y? 1 Inner inguinal fossa 



^Bladder, somewhat 

 distended 



Median umbilical ligament 



. Posterior surface of anterior abdominal wall of formalin subject. 



still slighter depressions corresponding approximately, in position to the outer part 

 of the posterior wall of the canal and to the external abdominal ring (page 1771) and 

 the lower fifth of the inguinal canal. When viscera make their way outward 

 from either of these depressions as the point of departure, the resulting hernia 

 is known as direct because it does not pass through the entire length of the inguinal 

 canal, but takes a shorter route, or i)iternal because it lies to the inner side of the 

 epigastric artery. A further examination of the structures (already described on 

 pages 523, 524) which are related to the production of inguinal hernia will serve to ex- 

 plain its occurrence in certain localities and in certain forms that may now be considered 

 separately in their simpler varieties, the rarer and more complicated being merely 

 mentioned or altogether omitted as unessential to the anatomical study of hernia. 



Oblique, external, or indirect inguinal hernia, which makes its exit from the abdo- 

 men at the internal ring, is i^tcomplete if it remains in the inguinal canal, complete if it 

 emerges at the external ring, and scrotal if it descends into the scrotum. In frequency 

 it bears about the same relation to the other form of inguinal hernia — the direct — as 

 inguinal herniae do to all other forms of hernia in males, — viz., from 95-97 per cent. 

 This frequency depends upon the following anatomical conditions, {a) The descent 

 of the testicle from behind the peritoneum (page 2040), carrying with it a process 

 (vaginal) of peritoneum, a portion of the transversalis fascia (infundibuliform fascia), 



