384: DIGESTION. 



inches. 1 Passing from the caecum, the canal diminishes in 

 calibre, gradually and very slightly, to where the sigmoid 

 flexure opens into the rectum. This is the narrowest portion 

 of the canal. Beyond .this, the rectum gradually increases 

 in diameter, forming a kind of pouch, which abruptly di- 

 minishes in size near the external opening, to form the anus. 



The general direction of the large intestine is from the 

 cascum in the right iliac fossa, to the left iliac fossa, thus sur- 

 rounding the convoluted mass formed by the small intestine, 

 in the form of a horse-shoe. From the caecum to the rectum 

 the canal is known as the colon. The first division of the 

 colon, called the ascending colon, passes almost directly up- 

 ward to the under surface of the liver ; the canal here turns 

 at nearly a right angle, passes across the upper part of the ab- 

 domen, and is called the transverse colon ; it then passes down- 

 ward at nearly a right angle, forming the descending colon. 

 The last division of the colon, called the sigmoid flexure, is 

 situated in the left iliac fossa and is in the form of the italic 

 letter 8. This terminates in the rectum, which is not straight, 

 as its name would imply, but presents at least three distinct 

 curvatures, as follows : it passes first in an oblique direction 

 from the left sacro-iliac symphysis to* the median line op- 

 posite the third piece of the sacrum ; it then passes down- 

 ward, in the median line, following the concavity of the sa- 

 crum and coccyx ; and the lower portion, about an inch in 

 length, turns backward to terminate in the anus. 



The form of the large intestine is peculiar. The caecum, 

 or caput coli, presents a rounded dilated cavity, continuous 

 with the colon above, and communicating by a transverse slit 

 with the ileum. At its lower portion is a small cylindrical 

 tube, from one to five inches in length, opening below and a 

 little posterior to the opening of the ileum, called the vermi- 

 form appendix. This is covered with peritoneum, and is pos- 

 sessed of a muscular and a mucous coat. It is sometimes en- 



1 BRINTON, Cyclopaedia of Anatomy and Physiology, London, 1859, vol. v., 

 supplement, p. 362. 



