436 ABDOMEN 



elvic 



which passes over the upper border of the parietal pel 

 fascia into the obturator canal. The nerves lie outside the 

 fascia, and, with the exception of the obturator nerve^ those which 

 are leaving the pelvis do not require to pierce the fascia, but 

 the branches which are to supply the viscera pass through its 

 substance to gain their terminations, and the obturator nerve 

 pierces it posteriorly to gain the interior of the pelvis. The 

 difference between the nerves and blood vessels can be well 

 studied by. an examination of the fascia as it passes over the 

 greater sciatic foramen. 



The relation of the pelvic blood-vessels to the lining fascia 

 is a matter of some practical importance. The margins of 

 the apertures in the fascia through which the vessels pass are 

 usually strengthened by some encircling fibres ; still, a portion 

 of gut may make its way through one or other of the openings 

 in the fascia and form a hernia. Sciatic hernia consists of 

 a protrusion of the gut through the greater sciatic foramen. 

 The hernia may be situated either above or below the 

 piriformis. In the former case it escapes through the 

 aperture in the fascia made by the superior gluteal artery, 

 and in the latter, either through the aperture for the inferior 

 gluteal artery or through that for the internal pudendal artery. 

 A hernia may occur through the obturator foramen also 

 (obturator hernia). In that case the gut follows the obturator 

 artery over the upper border of the fascia and through the 

 obturator canal. 



Intestinum Rectum. The rectum is the portion of the 

 large intestine which extends from the termination of the 

 pelvic colon, opposite the middle of the third piece of the 

 sacrum, to the point about 38 mm. (one and a half inches) 

 in front of the tip of the coccyx, that is, -to the apex of the 

 prostate in the male, and to the apex of the perineal body 

 in the female. At that point it bends abruptly backwards, 

 pierces the rectal layer of pelvic fascia, and becomes the ana] 

 canal. 



The rectum is about five inches long. For the greater 

 part of its length it is adapted to the anterior surfaces of the 

 sacrum and coccyx (Fig. 202). It is curved, therefore, with the 

 concavity forwards. Beyond the coccyx, the lower 38 mm. (one 

 inch and a half) of the rectum is supported by pelvic floor, 

 formed by the levatores ani muscles, and by the ano-coccygeal 

 body. The ano-coccygeal body consists of a dense mass of 



