THE PERITONEUM. 1047 



in the male and the round ligament in the female pass through this fascia ; the 

 point where they pass through is called the internal or deep abdominal ring. This 

 opening is not visible externally, owing to a prolongation of the transversalis fascia 

 on the structures forming the infundibuliform fascia. 



The internal or deep abdominal ring is situated in the transversalis fascia, mid- 

 way between the anterior superior spine of the ilium and symphysis pubis, and 

 about half an inch above Poupart's ligament. It is of an oval form, its long 

 diameter being directed upward and downward ; it varies in size in different sub- 

 jects, and is much larger in the male than in the female. It is bounded above and 

 externally by the arched fibres of the Transversalis muscle, below and internally 

 by the deep epigastric vessels. It transmits the spermatic cord in the male arid 

 the round ligament in the female. From its circumference, a thin, funnel-shaped 

 membrane, the infundibuliform fascia, is continued round the cord and testis, 

 enclosing them in a distinct pouch. When the sac of an oblique inguinal hernia 

 passes through the internal or deep abdominal ring, the infundibuliform fascia 

 constitutes one of its coverings. 



The Subperitoneal Areolar Tissue. Between the transversalis fascia and the 

 peritoneum is a quantity of loose areolar tissue. In some subjects it is of consider- 

 able thickness and loaded with adipose tissue. Opposite the internal ring it is 

 continued round the surface of the cord, forming a loose sheath for it. 



The deep epigastric artery arises from the external iliac artery a few lines above 

 Poupart's ligament. It at first descends to reach this ligament, and then ascends 

 obliquely along the inner margin of the internal or deep abdominal ring, lying 

 between the transversalis fascia and the peritoneum, and passing upward pierces 

 the transversalis fascia and enters the sheath of the Rectus muscle by passing over 

 the seinilunar fold of Douglas. Consequently the deep epigastric artery bears a 

 very important relation to the internal abdominal ring as it passes obliquely up- 

 ward and inward from its origin from the external iliac. In this part of its course 

 it lies along the lower and inner margin of the internal ring and beneath the com- 

 mencement of the spermatic cord. At its commencement it is crossed by the vas 

 deferens in the male and by the round ligament in the female. 



The peritoneum, corresponding to the inner surface of the internal ring, presents 

 a well-marked depression, the depth of which varies in different subjects. A thin 

 fibrous band is continued from it along the front of the cord for a variable distance, 

 and becomes ultimately lost. This is the remains of the pouch of peritoneum which, 

 in the foetus, precedes the cord and testis into the scrotum, the obliteration of 

 which commences soon after birth. In some cases the fibrous band can only be 

 traced a short distance, but occasionally it may be followed, as a fine cord, as far 

 as the upper end of the tunica vaginalis. Sometimes the tube <of peritoneum is 

 closed only at intervals and presents a sacculated appearance, or a single pouch 

 may extend along the Avhole length of the cord, which may be closed above, or the 

 pouch may be directly continuous with the peritoneum by an opening at its upper 

 part. 



In the female foetus the peritoneum is also prolonged in the form of a tubular 

 process for a short distance into the inguinal canal. This process is called the 

 canal of Nuck. It is generally obliterated in the adult, but sometimes it remains 

 pervious even in advanced life. 



In order to understand the relation of the peritoneum to inguinal hernia, it is 

 necessary to view the anterior abdominal wall from its internal aspect, when it will 

 be seen as shown in Fig. 582. Between the upper margin of the front of the 

 pelvis and the umbilicus, the peritoneum, when viewed from behind, will be seen 

 to be raised into five vertical folds, with intervening depressions, by more or less 

 prominent bands which converge to the umbilicus. One of these is situated in the 

 median line, and is caused by the urachus, the remnant of the allantois : it extends 

 from the summit of the bladder to the umbilicus. The fold of peritoneum covering 

 it is known as the plica urachi. On either side of this is a prominent band, caused 

 by the obliterated hypogastric artery, which extends from the side of the bladder 



