Till: INTESTINAL ('AXAL. 



1041 



In the second portion it covers the upper part of the anterior surface, a part of the 

 sides, and none of the posterior surface. The lower part is devoid of serous 

 covering. The peritoneum of the upper part of the rectum is thrown into a few 

 pouches, the appendices epiploicce. In women, where the cul-de-sac is lower than 

 in men. the peritoneum covers the whole of the anterior part of the middle 

 portion. 



The in>is<-nlar coat is thick ; the three bands of the colon do not spread out and 

 form the uniform layer as described. The anterior band descends along the mid- 

 dle portion of the rectum and continues to the anus. The external band joins the 

 anterior near the end of the sigmoid flexure and runs with it over the first part 

 of the rectum. The internal band is most marked along the middle portion of 

 the rectum and runs posteriorly to the anus. The three bands of the caecum and 

 colon are reduced to two on the rectum, an anterior and a posterior one. In pro- 

 portion as they descend they get larger. The endings of these fibres are various : 

 into pelvic fascia, anterior surface of coccyx, and deep surface of skin, just out- 

 side the anus. Tendencies to sacculation are described, as the longitudinal fibres 

 are rather short. The longitudinal layer is more or less complete between the 

 two bands. 



The c-ir<-ul.ai' fibres are well developed and especially thick between the sac- 

 culations. Below, in the anal portion, they become much augmented as the 

 Intern '/ itpliinctcr. This muscle is 3 cm. high, and 3 to 4 mm. thick ; below it is 

 precisely limited by the circular line, "white line," which marks the mucous 

 membrane from the skin. It surrounds the whole length of the anal canal and 

 ends very abruptly above in the thinner circular fibres. All these fibres are un- 

 striated. 



Posteriorly two Recto-coccygei muscles pass from the second or third vertebra 

 of the coccyx to the posterior part of the anal canal. 



The other muscles directly connected are the External sphincter, which de- 

 scends a little lower than the Internal and surrounds the anal orifice (Fig. 658), 

 and the Levator ani giving support on the sides. These have been described. 



The mni-i-'ii.it membrane of the rectum is thicker and more vascular than that 

 of the colon, and, moving quite freely on the muscular coat, makes a kind of 

 independent tube. When contracted it shows many folds of no special direction, 

 most of which can be obliterated : some, however, are more permanent, and are 



FIG. 659. Coronal section of pelvis. Posterior wall of rectum seen from in front. (Henle.) 



called valves of the rectum, or of Houston, or plicce recti. Usually three are 

 present, sometimes two or four. One of these, the largest and usually constant. 

 is situated on the right side of the rectum, about at the point where the perito- 



66 * 



