SOME POINTS IN THE ANATOMY OF THE DIGESTIVE SYSTEM. 55 



baiid, which occupies nearly the whole width of the anterior 

 aspect in the lower portion of the pelvic colon. The postero- 

 internal taenia spreads out in a similar manner on the back, so 

 that in the lower half of this colon the longitudinal layer of the 

 muscular coat is complete, with the exception of a narrow part 

 on each side; here, the circular fibres come to the surface, and 

 the intestine presents a series of small sacculations. These, 

 however, disappear, and the longitudinal fibres form a con- 

 tinuous layer all round as the rectum proper is approached. 



The Rectum. 



The rectum, following Jonnesco's division, may be described 

 as the comparatively dilated portion of the bowel between the 

 pelvic colon above and the anal canal below. Normally, it 

 probably forms only a temporary reservoir, in which the fseces 

 accumulate a short time before defaecation takes place ; as a 

 result of habit, however, this temporary function may be con- 

 verted into a more or less permanent one. 



Although Jonnesco states that the rectum begins (that is, 

 the pelvic mesocolon ends) most frequently opposite the disc 

 between the third and fourth sacral vertebra, it has been my 

 experience that the rectum commences more frequently above 

 than below the third piece of the sacrum. It ends opposite 

 the lower and back part of the prostate in the male, or at a 

 point 1^ inches in front of, but at a lower level than, the tip of 

 the coccyx in both sexes, where the bowel bends abruptly down- 

 wards and backwards, and piercing the pelvic floor passes into 

 the anal canal. Its general direction is downwards, but at its 

 upper end, following the curve of the rectum, it also slopes 

 slightly backwards ; its middle portion is practically vertical, but 

 the terminal third or more is directed downwards and forwards 

 at an angle varying from 45° to 60° with the horizontal. The 

 pelvic floor upon which it rests forms here a similar angle with 

 the horizontal. The bend which the bowel forms behind the 

 lower end of the prostate where the rectum passes into the anal 

 canal is, as pointed out above, abrupt, and usually approaches a 

 right angle, so that the anal canal itself slopes downwards and 

 backwards at an angle, as a rule, of from 30 to 45 degrees with 



