56 PROFESSOR A. BIRMINGHAM. 



the horizontal. Not uncommonly this latter curve represents 

 a knuckle-like projection, as seen on mesial section, immediately 

 aV>ove the anal canal. This is most marked in females, and some- 

 times appears as if the anterior wall of the bowel were doubled 

 back upon itself at this point. The floor of the cul-de-sac thus 

 formed may dip down in front, even below the level of the 

 upper aperture of the anal canal. This condition is most 

 common in multipara, and is evidently due to the relaxed con- 

 dition of the pelvic structures, the slight support afforded by the 

 perineal body to this part of the gut, and the great capacity 

 and shallowness of the pelvis in these. 



Although the sacculations which are so characteristic of the 

 large intestine cannot properly be said to exist in the rectum, 

 still it presents certain well marked inflexions which have been 

 described as lateral sacculations (Otis). The term ' sacculations ' 

 should, I think, be reserved for localised dilatations engaging a 

 part only of the wall of the gut ; if this is so, it cannot properly 

 be applied to the condition found in the rectum, which really 

 presents a series of flexures involving the whole tube, and 

 including in their inflexions the longitudinal muscular flbres. 

 When viewed from the front, the rectum is seen to be regularly 

 folded from side to side in a zigzag fashion, the folding being 

 slightly marked when the rectum is empty, but becoming much 

 more distinct with distension. In other words, when viewed from 

 the front, this division of the bowel presents in the majority of 

 cases three more or less distinct flexures. Of these, the upper 

 and lower have their concavities directed to the left as a rule ; 

 the third flexure, which is the best marked of the three, lies 

 between the other two, but on the right side. Not infrequently, 

 however, two flexures are on the right and one on the left. 

 There are thus produced three lateral inflections of the tube 

 as it passes from side to side, each of which appears on the ex- 

 terior as a transverse crease or angle, whilst in the interior they 

 project into the cavity of the bowel as three prominent cres- 

 centic shelves, known as the rectal valves (plicte transversales 

 recti ; valves of Houston or Kohlrausch), which help to support 

 the fftical contents when the rectum is distended. 



The rectum in animals generally is free from these inflections, 

 and the condition found in man is evidently an adaptation to the 



