536 DIGESTION. 



ment, and in them it becomes more indurated, by the absorption of the 

 fluid portions. In torpor of this part of the intestinal canal, the faeces 

 are retained, at times, so long, that they form hard balls or scybala; 

 and not unfrequently occasion the inflammation of the lining membrane 

 of the large intestine, which constitutes dysentery. The longitudinal 

 muscular fibres are concentrated into three ligamentous bands or fasci- 

 culi, which run the whole length of the intestine. These being shorter 

 than the intestine, pucker it, and are the occasion of the pouched or 

 saccated arrangement. The inner or circular muscular fibres are, like 

 those of the small intestine, uniformly spread over the surface, but are 

 stronger. Lastly, on the great intestine, especially the colon, are 

 numerous processes of the peritoneum containing fat, and hence called 

 appendiculse epiplo'icse and appendiculse pinguedinosse. These are seen 

 in greatest abundance on the right and left lumbar portions ot the 

 colon. 



The rectum terminates the intestinal canal, and extends from the end 

 of the colon to the anus. It commences about the fifth lumbar vertebra, 

 and descends vertically into the pelvis, following the concavities of the 

 sacrum and coccyx; and, consequently, is not straight, as its name 

 would import. At its upper part, there are a few appendiculse epiploicae ; 

 and a small duplicature of the mesentery, called mesorectum, attaches 

 it to the sacrum. It differs from the other intestines in becoming wider 

 in its progress downwards, and in its parietes being thicker. The lower 

 part of the mucous membrane exhibits several longitudinal folds or 

 rugae, called "columns," which have been considered as the effect of the 

 contraction of the circular fibres of the muscular coat. At the lower 

 ends of the wrinkles between the columns are small pouches, from two 

 to four lines in depth, the orifices of which point upwards. They are 

 occasionally the seat of disease, and, when enlarged, give rise to painful 

 itching. The nature of this affection was first pointed out by Dr. 

 Bhysick, and the remedy consists in slitting them open. The longi- 

 tudinal fibres of the muscular coat have a different arrangement from 

 that which exists in the other portions of the large intestine. They 

 are distributed over the whole surface, as in the small intestine, or 

 rather, as in the oesophagus. At the anus, an arrangement of the 

 muscular coat prevails, which has been pointed out by Professor Homer. 1 

 The longitudinal fibres, having reached the lower margin of the internal 

 sphincter, turn under this margin between it and the external sphincter, 

 and then ascend upwards for an inch or two in contact with the mucous 

 coat, into which they are finally inserted by fasciculi, which form the 

 base of the columns of the rectum : many of the fibres, however, termi- 

 nate also between the fasciculi of the circular fibres. The circular fibres 

 are more and more marked, as they approach the outlet, and, by cir- 

 cumscribing the margin of the anus, they form the sphincter ani muscle. 

 Immediately within the anus is the widest portion of the rectum ; and, 

 in this, accumulations of indurated faeces sometimes take place in old 

 people to a surprising extent, owing to torpor of the muscular powers 

 concerned in the expulsion of the faeces. The mucous coat of the rectum 

 is thick and red, and abounds in follicles. 



1 General Anatomy and Histology, 7th edit., ii. 50, Philada., 1846. 



