THE ABDOMEN, EXTERIOR. 461 



process, forming the infantile variety of rupture ; in this case 

 three layers of peritoneum intervene between the bowel and 

 skin ; or fluid may distend the tube, producing an encysted 

 hydrocele of the cord. 



Even if nature's processes are completed a hernia may 

 develop, pass out through the internal ring, inguinal canal, 

 and external ring. This is the indirect form of inguinal 

 hernia. If the hernial protrusion leaves through Hessel- 

 bach's triangle (see page 457) and appears at the external 

 ring, it becomes the direct form of inguinal hernia. 



The coverings of the indirect inguinal hernia are these : 

 The peritoneum, extraperitoneal tissue, the infundibuliform 

 fascia, the cremasteric fascia, the external spermatic fascia, 

 the superficial and deep layers of the superficial fascia, and 

 the integument. 



The direct inguinal hernia takes a course through Hessel- 

 bach's triangle and directly out through the external ring. 

 Its coverings are the peritoneum, extraperitoneal tissue, 

 fascia transversalis, conjoined tendon, external spermatic 

 fascia, two layers of the superficial fascia and the skin. 



DISSECTION. 



Raise the peritoneum from the iliac fossae, exposing the iliac vessels. This 

 shows how they may be reached and ligated without opening the peritoneum. 



Clean the extraperitoneal tissue from the surface of the peritoneum ; it will 

 be found thicker in the lower than the upper part. 



Find three fibrous cords passing from the umbilicus downward to the region 

 of the bladder. The two outside ones are the obliterated hypogastric arteries, 

 the middle one the urachus. The arteries return the blood in the foetus to the 

 placenta, the urachus connects the bladder with the allantois. By inflating 

 the bladder these cords can be easier dissected out, at the same time it will be 

 seen that the peritoneum does not cover the anterior wall of the bladder for a 

 distance of nearly two inches above the pubes. This area of bladder un- 

 covered by peritoneum and separated from the inside of the abdominal wall 

 by extraperitoneal tissue is the space of Retzius. Through this space supra- 

 pubic cystotomy is performed. 



