288 



DIGESTION. 



testine, in the form of a horseshoe. 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 upward 

 to the under surface of the liver ; 

 the canal here turns at nearly 

 a right angle, passes across the 

 upper part of the abdomen, and 

 is called the transverse colon ; 

 it then passes downward 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 S. 

 This terminates in the rectum, 

 which is not straight, as its 

 name would imply, hut presents 

 at least three distinct curva- 

 [20 tures, as follows : it passes first 



in an oblique direction from the 

 left sacro-iliac symphysis to the 

 median line opposite the third 

 piece of the sacrum; it then 

 passes downward, in the me- 

 dian line, following the con- 

 cavity of the sacrum and coc- 

 cyx ; and the lower portion, 

 which is about an inch in length, 

 turns backward to terminate in 

 the anus. 



The form of the large intes- 

 tine is peculiar. The c&cum, 

 or caput coli, presents a round- 

 ed, dilated cavity, continuous 

 with the colon above and com- 

 municating 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 ver- 

 miform appendix. This is covered with peritoneum and is possessed of a muscular and 

 a mucous coat. It is sometimes entirely free and is sometimes provided with a short 

 fold of mesentery for a part of its length. The coats of the appendix are very thick. 

 The muscular coat consists of longitudinal fibres only. The mucous membrane is pro- 

 vided with tubules and closed follicles, the latter frequently being very numerous. This 

 little tube, which is only about one-third of an inch in diameter, generally contains a 

 quantity of clear, viscid mucus. The uses of the vermiform appendix are unknown. 



Ileo-ccBcal Valve. The most interesting anatomical peculiarity of the ca3cum is the 

 opening by which it receives the contents of the small intestine. This opening is ar- 

 ranged in the form of a valve, known as the ileo-csecal valve, situated at the inner and 

 posterior portion of the caecum. The small intestine, at its termination, presents a 



FIG. 79. Stomach, pancreas, large intestine, etc. (Sappey.) 

 1, anterior surface of the liver: 2, gall-bladder; 3,3, section of the dia- 

 phragm ; 4, posterior surface of the stomach ; 5, lobus Spigelii of the 

 liver ; 6, cceliac axis ; 7, coronary artery of the stomach ; 8, splenic 

 artery; 9, spleen; 10, pancreas; 11, superior mesenteric vessels; 12, 

 duodenum ; 18, upper extremity of the small intestine ; 14, lower end 

 of the ileum; 15, 15, mesentery; 1 6. ccecum ; 17, appendix vermi- 

 tormis; 18, ascending colon; 19, 19, transverse colon; 20, de- 

 scending colon; 21, sigmoid Jlexwe of the colon; 22, rectum; 23, 

 urinary bladder. 



