318 A YEAR IN SCIENCE 



the food from passing out of the stomach as soon as it 

 enters. 



The stomach is lined with a mucous membrane. This 

 is larger than the stomach and is thrown into folds 

 running lengthwise of the organ. When examined with 

 a lens, this membrane is seen to be covered with 

 numerous small pits, which are the openings of many 

 little tubes formed by the folding of the mucous mem- 

 brane. This further increases the internal surface of 

 the stomach. Each tube is the outlet of a gastric gland. 

 These glands secrete another digestive fluid, the gastric 

 juice. 



Intestines. The intestines are divided into two 

 regions. The first, a tube about twenty feet long and 

 with a diameter varying from two inches near the 

 stomach to one inch at the other end, is called the 

 small intestine. The second, the large intestine, is about 

 five feet long with a diameter varying from two and 

 one-half to one and one-half inches. The general 

 arrangement of the two intestines is shown in the figure. 

 Notice how the small intestine enters the large one. 

 Projecting from the sack-like pouch at the beginning 

 of the large intestine is a worm-like extension, the 

 vermiform appendix. Inflammation of the appendix 

 causes the disease known as appendicitis. 



The small intestine, like the stomach, is lined by a 

 mucous membrane which is thrown into folds across 

 the tube. The surface of the mucous membrane is 



