SUBACUTE OBSTRUCTION OF THE PELVIC FLEXURE 125 



point with which we are dealing. We shall find these 

 in the anatomical arrangement and distribution of this 

 portion of the colon. 



The first point of importance is the fact that in this 

 position there is a somewhat marked constriction in the 

 lumen of the gut. Considering the two portions of the 

 colon forming the flexure — -namely, the second and the 

 third — we see at once that while the second portion, from 

 the suprasternal flexure backwards, is of considerable 

 size, the third is comparatively small. 



Further, we notice that the diminution in lumen is 

 not gradual, but that it occurs with some degree of 

 suddenness, thus occasioning the constriction referred to. 

 A glance at Fig. 8 will explain. 



It needs no great amount of demonstration to point 

 out that the circumference of the bowel taken around the 

 second portion at a point indicated by the dotted line a h, 

 is distinctly larger than when taken around the pelvic 

 flexure at c d. This, as a matter of fact, is more evident 

 with the actual bowel before one than with merely the 

 photograph to- refer to. It is distinctly more marked, 

 too, in an animal that has been taking a normal amount 

 of food. In the case from which this illustration was 

 taken the animal had died from a wasting disease, and 

 the bowels were comparatively empty. 



In so much as that to some extent it exaggerates this 

 difference in size between the second and the third 

 portions of the colon, Fig. 9 will more clearly illustrate it. 



This is a photograph of one of the several cases of 

 twist of the pelvic flexure that have come under my 

 notice. Here, owing to the displacement of the bowel, 

 the ingesta is prevented from passing out of the second 

 portion of the bowel into the third. The second portion 

 is therefore shown distended to the full with accumulated 



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