CHAPTER XII. 



THE LARGE INTESTINE AND THE PROCESSES WHICH 

 HAVE THEIR SEAT IN IT. THE F^CES IN HEALTH 

 AND DISEASE. THE INTESTINAL GASES. INTES- 

 TINAL CONCRETIONS. 



SECT. 1. PRELIMINARY OBSERVATIONS ON THE ARRANGEMENT 

 AND STRUCTURE OF THE LARGE INTESTINE. 



As we trace the small intestine from its commencement at the 

 pyloric end of the stomach we find that this long tube, which in man 

 possesses an average length of 20 feet, gradually diminishes in calibre 

 as we pass from duodenum to jejunum and from jejunum to ileum. 

 At the lower end of the latter the small opens suddenly into the, 

 much wider, large intestine or 'colon:' though not at the very com- 

 mencement of this, which is a cul-de-sac (the caput ccecum coli or 

 ccecum), but at a point a little removed from this. The margins of 

 the aperture by which the small intestine opens into the large, project 

 into the latter in such a manner that, while they readily permit the 

 passage of matters from small into large intestine, any backward 

 movement of the contents of the large intestine would have the 

 effect of compressing the lips of the opening and closing it; this 

 arrangement constitutes the ilio-ccecal or ilio-colic valve. Connected 

 with the caput ccecum coli is (in man and monkeys) a small diver- 

 ticulum, like a narrow glove-finger, called the vermiform appendix. 

 The first and greater part of the large intestine is known as the 

 colon, the last as the rectum. The colon is subdivided into ascending 

 colon, transverse colon, and descending colon, the bend made by the 

 transverse in passing into the descending colon, receiving the name 

 of the sigmoid flexure. The total length is from five to six feet. 



The arrangements of the coats of the large intestine are similar 

 to those of the small, though modifications in each of the constituent 

 coats are obvious. 



The mucous membrane is characterised by the absence of villi. 

 It presents innumerable glands built on the type of the glands of 

 Lieberkiihn of the small intestine, but very much larger and especially 

 much longer than these and possessing a wider lumen. Their epi- 



